HDR and WCG Principles-Part 2

Dr. Mohieddin Moradi
mohieddinmoradi@gmail.com
Dream
Idea
Plan
Implementation
1

https://www.slideshare.net/mohieddin.moradi/presentations
2

− Elements of High-Quality Image Production
− CRT Gamma Characteristic
− Light Level Definitions & HVS Light Perception
− Dynamic Range Management in Camera
− An Introduction to HDR Technology
− Luminance and Contrast Masking and HVS Frequency Response
− SMPTE ST-2084: “Perceptual Quantizer”(PQ), PQ HDR-TV
− ARIB STB-B67 and ITU-R BT.2100, HLG HDR-TV
− Scene-Referred vs. Display-Referred and OOTF (Opto-Optical Transfer Function)
− Signal Range Selection for HLG and PQ (Narrow and Full Ranges)
− Conversion Between PQ and HLG
− HDR Static and Dynamic Metadata
− ST 2094, Dynamic Metadata for Color Volume Transforms (DMCVT)
Outline
3

− Different HDR Technologies
− Nominal Signal Levels for PQ and HLG Production
− Exposure and False Color Management in HDR
− Colour Bars For Use in the Production of HLG and PQ HDR Systems
− Wide Color Gamut (WCG) and Color Space Conversion
− Scene Light vs Display Light Conversions
− Direct Mapping in HDR/SDR Conversions
− Tone Mapping, Inverse Tone Mapping, Clipping and Color Volume Mapping
− HDR & SDR Mastering Approaches
− Color Representation for Chroma Sub-sampling
− UHD Phases and HDR Broadcasting, Encoding and Transmission HDR
− Different Log HDR-TV Standards
− Sony S-Log3 HDR Standard
− SR: Scene-referred and Super Reality (Scene Referred Live HDR Production) (SR Live Workflow )
Outline
4

Scene
Light
SDR
Signal
Camera
HLG
Signal
PQ
Signal
Sensor
Relative Linear Scene Light
(Volts)
Lens
Set Exposure (Iris)
Relative
Non-linear Signal
[0,1]
Absolute
Non-linear Signal
[0,1]
A Closer Look at the Camera
SDR OETF
(“Gamma”)
HLG OETF
PQ OETF
Relative
Non-linear Signal
[0,1]
6

EOTF and OETF for Different HDR Systems
7

Image Quantisation
Original Extreme Banding
Recall: Banding, Contouring or Ringing
8

∆𝑳
𝑳
= 𝑪𝒐𝒏𝒔𝒕𝒂𝒏𝒕 (≈ 𝟎. 𝟎𝟐)
Masker: Background 𝑳𝟏 (one stimulus)
Disk: Another stimulus 𝑳𝟏 + ∆𝑳𝟏
In the brighter parts of an image
∆𝑳
𝑳
Masker: Background 𝑳𝟐(one stimulus)
Disk: Another stimulus 𝑳𝟐 + ∆𝑳𝟐
In the dark parts of an image
Masker: Background 𝑳𝟐(one stimulus)
Disk: Another stimulus 𝑳𝟐 + ∆𝑳𝟐
∆𝑳𝟏 = 𝜶𝟏𝑳𝟏
∆𝑳𝟐 = 𝛂𝟐𝑳𝟐
Masker: Background 𝑳𝟏(one stimulus)
Disk: Another stimulus 𝑳𝟏 + ∆𝑳𝟏
∆𝑳𝟏 > ∆𝑳𝟐 ∆𝑳𝟏 > ∆𝑳𝟐
𝜶𝟐 > 𝜶𝟏
Weber-Fechner law and De Vries-Rose law
𝜶𝟐 = 𝜶𝟏 ≈ 𝟎. 𝟎𝟐
∆𝑳𝟏 = 𝜶𝟏𝑳𝟏
∆𝑳𝟐 = 𝛂𝟐𝑳𝟐
∆𝐿
𝐿
= 𝑪 (≈ 𝟎. 𝟎𝟐)
∆𝐿
𝐿
= 𝐾
∆𝐿
𝐿
=
𝐾
𝐿
9

Weber-Fechner law
Weber Fraction
∆L/L, Linear scale
Background Luminance, L (millilamberts), Log scale
∆𝑳
𝑳
In ∆𝑳, the object can be noticed by the HVS with a 50% chance.
Masker: Background 𝑳 (one stimulus)
Disk: Another stimulus 𝑳 + ∆𝑳
In the brighter parts of an image
Minimum Detectable Contrast
∆𝐿
𝐿
∆𝑳 𝒊𝒔 𝒂 𝒄𝒐𝒏𝒔𝒕𝒆𝒏𝒕 𝒑𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒐𝒇 𝑳
10

Weber-Fechner law
– The Weber-Fechner law is a classical representation of contrast sensitivity.
– According to this law, the minimum detectable contrast, i.e. the reciprocal of contrast sensitivity, is
constant regardless luminance.
– It is believed that the ratio is between 1/50 and 1/100. However, it increases below and above certain
luminances.
– In the brighter parts and highlights of an image the threshold for perceiving quantization error (banding or
contouring) is approximately constant, so quantization distortion visibility is constant.
Minimum Detectable Contrast
∆𝐿
𝐿
11

De Vries-Rose law, (Hessel de Vries, Albert Rose)
De Vries-Rose law
– In the low lights it becomes increasingly difficult to perceive banding.
– That is, the threshold of visibility for banding becomes higher as the image gets darker.
– It means for small values of 𝑳, with decreasing the 𝑳, ∆𝑳 is increased and is more percentage of
background luminance L.
– Note that for two values 𝑳𝟏 < 𝑳𝟐 ⇒ ∆𝑳𝟏< ∆𝑳𝟐 because ∆𝑳 = 𝑲 𝑳.
.
∆𝐿
𝐿
= 𝐾 𝐿 ↓ ∆𝐿 𝑖𝑠 𝑚𝑜𝑟𝑒 𝑝𝑒𝑟𝑐𝑒𝑛𝑡𝑎𝑔𝑒 𝑜𝑓 𝐿
⇒
∆𝐿
𝐿
=
𝐾
𝐿
12

log10 ∆𝐿 = log10 𝐶 + log10 𝐿
∆𝑳
𝑳
= 𝑪
∆𝑳
𝑳
= 𝑲 log10 ∆𝐿 = log10 𝐾 +
1
2
log10 𝐿
⇒
⇒
L (millilamberts), Log scale
Threshold
∆L (millilamberts), Log scale
Slope=1
Slope=1/2
Weber-Fechner law and De Vries-Rose law
13

Contrast Sensitivity
– This graph is redrawn from Schreiber’s Fundamentals of Electronic Imaging Systems.
At very low luminance values, the curve departs from logarithmic
behaviour and approximates a square-root; this characteristic is
called the de Vries-Rose law (Hessel de Vries, Albert Rose).
The flat portion of the curve shows that the
perceptual response to luminance – termed
lightness – is approximately logarithmic.
∆𝑳
𝑳
= 𝑪 ≈ 𝟎. 𝟎𝟐
Slope=0.5
The transition occurs between absolute
luminance values of 0.1 to 1 nt.
(0.025)
(0.0158)
(0.039)
(0.063)
(0.1)
(0.158)
(
∆𝑳
𝑳
)
Quantization Effects (Banding): The Schreiber Threshold
∆𝑳
𝑳
= 𝑲
Over a range of luminance values of about
300:1, the discrimination threshold of vision is
approximately a constant ratio of luminance. 𝑺 =
𝟏
𝑪𝒎𝒊𝒏
𝑪𝒎𝒊𝒏 =
∆𝑳𝒎𝒊𝒏
𝑳
14

0.03
0.02
0.01
0
0.04
0.05
0.06
0.07
0.08
0.1
0.09
0.01 0.1 100 1000 10000
Weber
Fraction
1 10
Display Luminance cd/m²
Schreiber
De Vries-Rose Law
Critical Contrast ∆𝑳 = 𝑲 𝑳
Weber–Fechner Law
Critical Contrast ∆𝑳 = 𝑪𝑳 ≈ 𝟎. 𝟎𝟐𝑳
∆𝑳
𝑳The actual CSF varies with the screen luminance, field of view, spatial frequency of the
image, etc. Barten’s model takes such conditions into account.
15

100
Minimum Detectable Contrast (%)
Minimum Contrast Step (%)
L: Luminance (nit)
Contouring
(Banding)
∆𝑳
𝑳
×100
Above Threshold
• Step edges are visible
• Visible contouring/banding
Below Threshold
• Step edges are invisible
• Smooth gradients
Barten Ramp
• ITU-R Report BT.2246
• Consensus threshold of human
visibility for normal images
∆𝑳 & L are Large ⇒ Less bits are required ⇒
Larger quantize step size
∆𝑳 & L are small ⇒ More bits are required ⇒
Smaller quantize step size
∆𝑳
𝑳
×100
∆𝑳
𝑳
×100
Barten Ramp
In the dark areas, the
threshold of visibility
for banding becomes
higher as the image
gets darker.
• The Barten Ramp is an extremely handy graph that plots out where most people can begin
to see banding in a gradient (ie, the steps between each shade, (𝑳 to 𝑳 + ∆𝑳 is perceivable
or not)) when mapping out all the way to 10,000 nits for potential HDR imagery.
• The area in green shows where no banding can be seen but the area in red shows where
banding can be seen and is therefore problematic.
Contouring
(Banding)
De Vries-Rose Law
Weber–Fechner Law
𝑳 ↓⇒ ∆𝑳 𝒊𝒔 𝒎𝒐𝒓𝒆 𝒑𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒐𝒇 𝑳 ∆𝑳 𝒊𝒔 𝒂 𝒄𝒐𝒏𝒔𝒕𝒆𝒏𝒕 𝒑𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒐𝒇 𝑳
16
The threshold for
perceiving banding is
approximately constant
in the brighter parts and
highlights of an image.

Above Threshold
Below Threshold
Barten Ramp
100
Minimum
Contrast
Step
(%)
Luminance (nit)
∆𝑳
𝑳
×
100
SDR (LCD, BT. 1886 Gamma)
The experience has shown that with realistic
camera noise levels, the slight quantization
artefacts predicted for 100 nits ITU-R BT.1886
are masked and thus do not present real
problems in television production.
BT. 1886 Performance in 8-Bit, 10-Bit and 15-bit for SDR
Optical
Electronic
OETF
(Camera Gamma)
How many bits is required for
avoiding banding effect?
17

Above Threshold
Below Threshold
Barten Ramp
100
Minimum
Contrast
Step
(%)
Luminance (nit)
∆𝑳
𝑳
×
100
HDR
BT. 1886 Performance in 12-Bit and 15-bit for HDR
Optical
Electronic
OETF
(Camera Gamma)
It
waste
bits
in
bright
regions
Banding
18

Sensitivity of the HVS to Potential Gamma Levels
– Levels below this dashed line are invisibly small to humans and levels above the line are potentially visible
– Lines above the threshold curve may exhibit visual artefacts, so traditional gamma is not OK for HDR.
EOTF used by today’s TV
systems, with 8-bit quantization
Result of extending traditional gamma
curve to a 10-bit gamma EOTF
EOTF used by today’s TV systems,
with 10-bit quantization..
SMPTE 10-bit: One of the
proposals for an EOTF that
has a better match over HDR
The dashed line shows the limit of human ability to
detect steps in luminance levels.(Bartens
Threshold: (L to L+dL is perceivable or not))
Luminance levels
19

Perceptual Quantizer (PQ) Electro-Optical Transfer Function (EOTF)
Code words are equally spaced in perceived brightness over this range of luminance.
Equally
Spaced
Code
Words
(10
bits)
Standardized as SMPTE ST-2084 and ITU-R BT.2100 (10 bit)
PQ HDR Display
Perceived Brightness
𝑭𝑫: Display Luminance
𝐹𝐷=EOTF[𝐸′
]=10000 Y
𝐸′
𝑚1 = 0.1593017578125
𝑚2= 78.84375
𝑐1= 0.8359375
𝑐2= 18.8515625
𝑐3= 18.6875
𝑌 =
max ሖ
𝐸
1
𝑚2 − 𝑐1 , 0
𝑐2 − 𝑐3
ሖ
𝐸
1
𝑚2
1
𝑚1
𝑬′ (video level) denotes a non-linear
colour value {𝑹′, 𝑮′, 𝑩′} or { 𝑳′, 𝑴′, 𝑺′} in
PQ space in the range [0:1]
𝐹𝐷
20

Code Levels Distribution in HDR
Uniform (equally spaced) Code Words for Perceived Brightness
21

More Code Words
for Dark Area
Less Code Words for
Bright Area
22

Code Words Utilization by Luminance Range in PQ
• PQ headroom from 5000 to 10,000
nits = 7% of code space
• 100 nits is near the midpoint of the
code range
23

4 129 254 379 504 629 754 879 1019
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
𝐜𝐝/𝐦𝟐
10 Bit Code Value
PQ Display Luminance Defined by Absolute Code Value
Display-referred
Image Data
SMPTE ST 2084
PQ 10K EOTF
Display Peak Luminance= 10000 nits
The PQ curve’s maximum brightness is always mapped to the
maximum brightness of the reference display to ensure the highest
fidelity if the reference and consumer display have similar properties.
4000 nits
2000 nits
3000 nits
1000 nits
24

10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
0
𝐜𝐝/𝐦𝟐
12 Bit Code Value: 16 516 1016 1516 2016 2516 3016 3516 4079
10 Bit Code Value: 4 129 254 379 504 629 754 879 1019
8 Bit Code Value: 1 32 64 95 126 157 189 220 255
SMPTE ST 2084
PQ 10K EOTF
4000 nits
2000 nits
3000 nits
1000 nits
Display-referred
Image Data
The PQ curve’s maximum brightness is always mapped to the
maximum brightness of the reference display to ensure the highest
fidelity if the reference and consumer display have similar properties.
25

4 129 254 379 504 629 754 879 1019
1000
900
800
700
600
500
400
300
200
100
0
SMPTE ST 2084
𝐜𝐝/𝐦𝟐
PQ 1K EOTF
10 Bit Code Value
4 129 254 379 504 629 754 879 1019
4000
3600
3200
2800
2400
2000
1600
1200
800
400
0
SMPTE ST 2084
𝐜𝐝/𝐦𝟐
PQ 4K EOTF
10 Bit Code Value
Display-referred
Image Data
Display Peak Luminance= 1000 nits Display Peak Luminance= 4000 nits
− The PQ curve’s maximum brightness is always mapped to the maximum brightness of the reference display
to ensure the highest fidelity if the reference and consumer display have similar properties.
26

Perceptual Quantizer (PQ) Electro-Optical Transfer Function (EOTF) on Barten Ramp
Optical
Electronic
OETF
(Camera Gamma)
Visible Difference between shades resulting in banding
Smooth gradient with no discernable difference between shades
∆𝑳
𝑳
×
100
Minimum
Contrast
Step
(%)
Luminance (nit)
27

Visually Observable Levels per F-Stop (Barten)
1 Stop Luminance Range
# of Visible
Levels
8192 – 4096 cd/m² 276
4096 – 2048 cd/m² 275
2048 – 1024 cd/m² 274
1024 – 512 cd/m² 271
512 – 256 cd/m² 266
256 – 128 cd/m² 260
128 – 64 cd/m² 251
64 – 32 cd/m² 238
32 – 16 cd/m² 224
16 – 8 cd/m² 206
8 – 4 cd/m² 186
4 – 2 cd/m² 165
1 Stop Luminance Range
# of Visible
Levels
2 – 1 cd/m² 142
1 – 1/2 cd/m² 120
1/2 – 1/4 cd/m² 99
1/4 – 1/8 cd/m² 79
1/8 – 1/16 cd/m² 62
1/16 – 1/32 cd/m² 48
1/32 – 1/64 cd/m² 36
1/64 – 1/128 cd/m² 27
1/128 – 1/256 cd/m² 20
1/256 – 1/512 cd/m² 15
1/512 – 1/1024 cd/m² 11
1/1024 – 1/2048 cd/m² 8 28

12 Bit PQ – Puts Levels Where They are Needed
(4096 Levels)
29

BT.1886 and PQ Performances in 10-Bit for HDR
Minimum
Contrast
Step
(%)
Display luminance (cd/𝒎𝟐
)
– Result of extending existing
(traditional) gamma BT.1886 curve
to a 10-bit gamma EOTF (without
any change to the value of
gamma)
– BT. 1886 EOTF used by today’s TV
10 bit PQ 10,000 nit
Large Contrast Step Small Contrast Step
∆𝑳
𝑳
×
100
30

BT.1886 and PQ Performances in 12-Bit for HDR
12 bit PQ 10,000 nit
– Result of extending existing
(traditional) gamma BT.1886 curve
to a 12-bit gamma EOTF (without
any change to the value of
gamma)
– BT. 1886 EOTF used by today’s TV
Large Contrast Step Small Contrast Step
∆𝑳
𝑳
×
100
)
Minimum
Contrast
Step
(%)
31

OpenEXR Raster Image Format
– OpenEXR: Open Extended Dynamic Range
– It is an open source image format created by Industrial Light and Magic with the purpose of being used as
an image format for special effects rendering and compositing.
– The format is a general purpose wrapper for the 16 bit half-precision floating-point data type, Half.
– The Half format, or binary16, is specified in the IEEE 754-2008 standard.
– OpenEXR also supports other formats such as both floating-point and integer 32 bit formats. Using the Half
data type the format will have 16 bits per channel, or 48 bits per pixel.
– The OpenEXR format is able to cover the entire visible gamut and a range of about 10.7 orders of
magnitude with a relative precision of 0.1%.
– Based on the fact that the human eye can see no more than 4 (or 5) orders of magnitude simultaneously,
OpenEXR makes for a good candidate for archival image storage.
32

PQ: Most efficient use of bits
throughout entire range with
precision below threshold of
visibility
SMPTE ST-2084: “Perceptual Quantizer”(PQ)
EXR: Well below Barten threshold = Invisible contrast steps
∆𝑳
𝑳
×
100
33

Design of the PQ Non-Linearity
Barten Ramp: 10-bit Quantization Noise visibility @ 0.01 – 1000 Nits
Contouring
− Though the signal lines all come above the threshold curve to some
extent, experience has shown that with realistic camera noise levels,
the slight quantization artefacts predicted for 100 nits ITU-R BT.1886 or
10000 nits PQ are masked and thus do not present real problems in
television production.
Larger Contrast Step Size Smaller Contrast Step Size
Minimum
Contrast
Step
(%)
)
∆𝑳
𝑳
×
100
Weber–Fechner Law
Critical Contrast or ∆𝑳 = 𝑪𝑳 ≈ 𝟎. 𝟎𝟐𝑳
2
34

Design of the PQ Non-Linearity
Barten Ramp: 12-bit Quantization Noise visibility @ 0.001 – 1000 Nits
– In PQ can be shown 0.00005 up to 10000 nits (~27.6 Stop).
– Lines which fall below Barten curve will not exhibit any visible
quantization artefacts (such as image banding).
– Lines above the Barten curve may exhibit visual artefacts
)
Minimum
Contrast
Step
(%)
∆𝑳
𝑳
×
100
Larger Contrast Step Size Smaller Contrast Step Size
2
Weber–Fechner Law
35

12 bit uniform JND curves
Code words are equally spaced in perceived brightness over Luminance
JNDs Based on Barten Model
− Human perceptible units called “Just Noticeable Difference” (JND); 1JND=the minimum noticeable difference for human.
− Uniform JND: When bit depth is limited, the code words are distributed evenly over perceived brightness and errors are
minimized.
⇒ By this approach, there are less code values wasted to encode sub JND steps in areas where JNDs are larger
∆𝑳
𝑳
×
100
Weber–Fechner Law
36

𝐶𝑆𝐹(𝑢)
Barten Parameters Chosen Conservatively
I. 40º angular size
II. Varied spatial frequency at every luminance level to track peaks of the CSF (Contrast Sensitivity Function)
III. Select peak luminance level
IV. Iteratively calculate the rest of the steps
37

𝐶𝑆𝐹(𝑢)
38

𝑀𝑜𝑑𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑇ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 𝑚𝑡 ≜ 1
𝐶𝑆𝐹 𝑢
Also
𝑀𝑜𝑑𝑢𝑙𝑎𝑡𝑖𝑜𝑛 𝑇ℎ𝑟𝑒𝑠ℎ𝑜𝑙𝑑 𝑚𝑡=
𝐿𝑚𝑎𝑥−𝐿𝑚𝑖𝑛
𝐿𝑚𝑎𝑥−𝐿𝑚𝑖𝑛
Once we know the sensitivity CSF(u), we also know the modulation threshold
𝐿𝑒𝑣𝑒𝑙𝑠 𝐿𝑗+1 = 𝐿𝑗
1+𝑓.𝑚𝑡
1−𝑓.𝑚𝑡
Choose peaks of 100, 1000, and 10,000 nits as before
Then pick 𝑓 so that a near zero minimum level is reached
(Pick JND fraction 𝑓 such that a near-zero bottom level is reached at the other end of the range)
– 0 to 100 nits, 𝒇 = 𝟎. 𝟒𝟔 JNDs per code word at 12 bits
– 0 to 1000 nits, 𝒇 = 𝟎. 𝟔𝟖 JNDs per code word at 12 bits
– 0 to 10,000 nits, 𝒇 = 𝟎. 𝟗 JNDs per code word at 12 bits
Merging with pick JND fraction, 𝒇
39

Generalized OOTF from ITU-R BT.1886 in Combination with ITU-R BT.709
– We want the image from an SDR source and that from an HDR source to match everywhere the HDR
image brightness overlaps the range of the SDR source (i.e. for less than 100 nits).
– In order to maximize compatibility with existing SDR signals, it is desired an OOTF consistent with the
effective OOTF of existing practice which is:
– This maximizes compatibility for mixed source applications wherein some sources are HDR and some are
SDR.
SDR Signal
PQ HDR Signal
with less than 100 nits
luminance
• It maximize compatibility for PQ
HDR content less that 100 nits.
• It emulates the “look” of ITU-R
BT.709 plus ITU-R BT.1886 for
display light up to the limit of SDR
SDR Display
PQ HDR Display
𝑂𝑂𝑇𝐹𝑆𝐷𝑅 = 𝐸𝑂𝑇𝐹1886[𝑂𝐸𝑇𝐹709]
PQ HDR Signal
(up to 10000 nits)
40

– It is only needed to extend the range of 𝑶𝑬𝑻𝑭𝟕𝟎𝟗 and 𝑬𝑶𝑻𝑭𝟏𝟖𝟖𝟔 for HDR.
– The extension factor for displayed light is 100.
– As the SDR OOTF has a roughly gamma = 1.2 characteristic at the high end, the extension relative to scene
light (the input to OOTF) is approximately
– It means that if we extend SDR OOTF for getting 10000 nits output, then the extension factor for the linear
scene light is about 46.42.
– For creating 𝐺709, the 𝐸𝑆𝐷𝑅 should be replace by 59.5208𝐸𝑆𝐷𝑅 in 𝑶𝑬𝑻𝑭𝟕𝟎𝟗 because 𝐸𝐻𝐷𝑅 = 59.5208𝐸𝑆𝐷𝑅
(𝐸𝐹𝑆)𝛾
= 𝐸𝐹𝐷
𝐸𝐹𝐷 =
𝐿𝐻𝐷𝑅
𝐿𝑆𝐷𝑅
=
10000
100
= 100
𝐸𝐹𝑆 = 100(
1
1.2
)
= 46.42.
When the exact equations for ITU-R BT.709 and BT.1886 are used, the extension for HDR is 59.5208.
41

– To expand the range of 𝑂𝐸𝑇𝐹709 to 𝐺709 for HDR the equation is therefore:
– Note: HDR E is normalized to range of 0 to 1
– Consequently, the range of 𝑬′ is [𝟎, 𝟔. 𝟖𝟏𝟑] for HDR while it remains [0,1] for SDR.
𝑬 = 𝟏 ⇒ 𝐸′
= 6.813
𝑬 =
𝟏
𝟓𝟗. 𝟓𝟐𝟎𝟖
⇒ 𝐸′
= 1
𝑬 = 𝟎 ⇒ 𝐸′
= 0
𝐸′ = 𝐺709 𝐸 =
1.099(59.5208𝐸)0.45 − 0.099
0.018
59.5208
< 𝐸 < 1
4.5(59.5208𝐸) 0 < 𝐸 <
0.018
59.5208
𝐸′
= 𝐺709 𝐸 = ቊ1.099(59.5208𝐸)0.45 − 0.099 0.0003024 < 𝐸 < 1
267.84𝐸 0 < 𝐸 < 0.0003024
𝑉 = 𝐺709 𝐿 = ൝
1.099(𝐿)0.45 − 0.099 0.018 < 𝐿 < 1
4.5(𝐿) 0 < 𝐿 < 0.018
𝐿 : luminance of the image 0 <𝐿< 1
𝑉 : corresponding electrical signal
SDR OETF, 𝑶𝑬𝑻𝑭𝟕𝟎𝟗
Extended SDR OETF, 𝑮𝟕𝟎𝟗
HDR
SDR
42

– To expand the range of 𝐸𝑂𝑇𝐹1886 to 𝐺1886 for HDR no change to the equation is necessary, the argument is
simply allowed to extend to 6.813 and hence the range increases from 100 to 10 000:
– These extensions satisfy the boundary conditions:
𝑬 = 𝟏 ⇒ 𝐸′
= 6.813 ⇒ A displayed luminance of 10 000 cd/m²
𝑬 =
𝟏
𝟓𝟗.𝟓𝟐𝟎𝟖
⇒ 𝐸′
= 1 ⇒ A displayed luminance of 100 cd/m²
FD = G1886[E'] = 100 E′ 2.4
FD = OOTF[E] = G1886 [G709[E]] =G1886 [E′] = 100𝐸′2.4
𝐸′
= 𝐺709 𝐸 = ቊ1.099(59.5208𝐸)0.45
− 0.099 0.0003024 < 𝐸 < 1
267.84𝐸 0 < 𝐸 < 0.0003024
𝑳 = 𝒂(𝐦𝐚𝐱 𝑽 + 𝒃 , 𝟎 )𝜸
𝑬𝑶𝑻𝑭𝟏𝟖𝟖𝟔 𝑮𝟏𝟖𝟖𝟔
The extension factor for
displayed light is 100.
𝑳 = (𝑽)𝜸
43

– The x-axis, is the same as 𝑬 for SDR while for HDR it is 𝟓𝟗. 𝟓𝟐𝟎𝟖𝑬 since the domain of 𝑬 is [0,1]:
OOTF[E] = G1886 [G709[E]]
• OETF709 is expanded to G709 for HDR
• EOTF1886 is expanded to G1886 for HDR
𝑶𝑶𝑻𝑭𝑺𝑫𝑹 = 𝑬𝑶𝑻𝑭𝟏𝟖𝟖𝟔[𝑶𝑬𝑻𝑭𝟕𝟎𝟗]
𝑶𝑶𝑻𝑭𝑯𝑫𝑹 = 𝑶𝑬𝑻𝑭𝑷𝑸 × 𝑬𝑶𝑻𝑭𝑷𝑸
FD
E
𝑬 =
𝟏
𝟓𝟗. 𝟓𝟐𝟎𝟖
°
44

Actual OOTFs from Manually Graded Content
Comparison of proposal OOTF with the actual OOTFs by
manually grading camera RAW output:
– The OOTF is the ratio of the graded linear output to
the RAW linear input.
– Figure shows several examples from the HDR
sequence “Fantasy Flights”:
– These Figures show:
• Scatter plots of the log of the output luminance derived
from the PQ grade
versus
• The log of the relative input luminance derived from the
ARRI RAW camera output
For comparison, the OOTF from the
combination of Recommendations ITU-R
BT.1886 and BT.709 are plotted in white.
These scatter plots are colour-coded (RGB) to match the
images shown in the lower right corner of each figure.
Toe
45

Actual OOTFs from Manually Graded Content
– This shows that the extracted OOTFs are, as one
would expect, a bit brighter than SDR.
– Some preliminary conclusions can be drawn from
this experimental data:
1. For this manually graded content, the OOTF is
not a straight line, and thus the actual OOTF
does not correspond to an overall “system
gamma”.
2. Darker indoor scenes tend to be noise limited at
the bottom end and the OOTF exhibits a very
clear toe.
3. The extracted OOTFs appear to have roughly
the same curvature in the mid-tones as the
proposed model.
For comparison, the OOTF from the
combination of Recommendations ITU-R
BT.1886 and BT.709 are plotted in white.
These scatter plots are colour-coded (RGB) to match the
images shown in the lower right corner of each figure.
Toe
46

Resultant PQ OETF from Generalization
– OOTF can be combined with the
inverse of the EOTF to produce an OETF.
– In actual cameras, there is noticeable
noise at low signal levels, and in
practice the OETF slope at low levels is
limited so as to “crush” the noise in
black, thereby putting a “toe” into the
response.
– The reference OETF does not have such
a “toe”, but one is apparent in the
OOTF plot for the indoor scene of
“Fantasy Flights” shown above.
Toe
• It imulates the “look” of ITU-R BT.709 plus ITU-R BT.1886 for display light
up to the limit of SDR
• It Facilitates mixing of legacy ITU-R BT.709 signals and PQ HDR signals
• It Offers reasonable behavior for levels above those of SDR.
OETFPQ, Camera = OOTFPQ, Camera × EOTF −𝟏
PQ, Camera
𝑬 𝑬′
PQ encoded
color value
The signal determined
by scene linear light
Scene
Light
OOTF
PQ
𝑬𝑶𝑻𝑭−𝟏
PQ OETF
47

The PQ HDR system generates content that is optimum for viewing on
I. A Reference Monitor
• 0.005 nits up to 10 000 nits, capable of showing the entire color gamut
II. A Reference Viewing Environment
• The viewing environment would ideally be dimly lit, with the area surrounding the monitor being a neutral grey
(6500 degree Kelvin) at a brightness of 5 nits.
Why Display Mapping (DM)
– Content often must be viewed or produced in environments brighter than the reference condition, and on
monitors that cannot display the deepest blacks or brightest highlights that the PQ signal can convey.
– Display Mapping can take the form of an EETF (Electrical-electrical Transfer Function) in the display.
Display Mapping and EETF (Electrical-electrical Transfer Function)
Scene
Light
OOTF
PQ
EOTF-1
EETF EOTF
Display
Light
PQ signal
48

This functions provide a toe and knee to gracefully roll off
the highlights and shadows providing a balance between
preserving the artistic intent and maintaining details.
Toe
Knee
EETF EOTF
Display
Light
PQ signal
Display Mapping and EETF (Electrical-electrical Transfer Function)
To “crush” the
noise in black,
49

Artistic OOTF
• If an artistic image “look” different from that produced by the reference OOTF is
desired, “Artistic adjust” may be used.
• An artistic adjustment may be used to further modify the creative intent of the image
The PQ EOTF replaces the BT.1886 function
of SDR HDTV, and the corresponding PQ
OETF replaces the BT.709 OETF as the
default camera capture curve.
A display adjustment is used to adapt the signal for
different display characteristics and display environments.
PQ HDR-TV system Architecture
No use of metadata is shown or required.
Camera
Sensor
Image
Display
Adjust
Creative
Intent
PQ
EOTF
PQ
EOTF
Reference
OOTF
Artistic
Adjust
PQ
EOTF −𝟏
PQ OETF
50

Reference OOTF = OETF (PQ) + EOTF (PQ)
– Opto-Electronic Transfer Function (OETF): Scene light to electrical signal
– Electro-Optical Transfer Function (EOTF): Electrical signal to scene light
OOTF (Opto-Optical Transfer Function)
PQ OETF PQ EOTF
𝑬: [𝟎, 𝟏] 𝑬′
: [𝟎, 𝟏]
𝑭𝑫
Linear Scene-light
Signals 𝑹𝒔, 𝑮𝒔, 𝑩𝒔
Non-linear
Linear Display-light
Signals 𝑹𝑫, 𝑮𝑫, 𝑩𝑫
𝑭𝑺
51

PQ OETF PQ EOTF
𝑬: [𝟎, 𝟏] 𝑬′
: [𝟎, 𝟏]
Linear Scene-light
Non-linear
Non linear color value,
encoded in PQ space in
the range [0,1].
The signal determined by scene
linear light, scaled by camera
exposure in the range [0:1].
𝑭𝑫 :The luminance of a displayed linear
component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫, in cd/m².
The luminance of a single colour component (𝑹𝑫, 𝑮𝑫,
𝑩𝑫), means the luminance of an equivalent achromatic
signal with all three colour components having that
same value.
𝑭𝑫
𝑭𝑺
52

– There are different type of signal formats; 𝑅𝐺𝐵, 𝑌𝐶𝑟𝐶𝑏 and 𝐼𝐶𝑇𝐶𝑃.
– 𝑭𝑫 is the luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫, in cd/m².
– The luminance of a single colour component (𝑹𝑫, 𝑮𝑫, 𝑩𝑫 ), means the luminance of an equivalent
achromatic signal with all three colour components having that same value.
Equivalent Achromatic Signal Equivalent Achromatic Signal Equivalent Achromatic Signal
𝑌′
= 0.2126𝑅′
+ 0.7152𝐺′
+ 0.0722𝐵′
𝑌 = 0.2126𝑅 + 0.7152𝑅 + 0.0722𝑅 𝑌 = 0.2126𝐺 + 0.7152𝐺 + 0.0722𝐺 𝑌 = 0.2126𝐵 + 0.7152𝐵 + 0.0722𝐵
53

To display HDR accurately, same settings between OETF of camera and EOTF of display are needed!!
--> Different settings make HDR signal and display to look wrong
Linear Scene Light
Cancel
OOTF=Artistic Intent
(seasoning)
EOTF-1
OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
OETF
Optical Signal
Scene Light
Electronic Signal
EOTF
OOTF Position in PQ
Display-Referred Signal
Output [%]
Input [cd/㎡ ]
Display Linear Light
54

Linear Scene Light
Cancel
(seasoning)
EOTF-1
OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
OETF
Optical Signal
Scene Light
Electronic Signal
EOTF
OOTF Position in PQ
Output [%]
Input [cd/㎡ ]
The PQ system specifies a display-referred HDR signal which means that the PQ signal describes the
absolute output light from the mastering display.
• Therefore, the mastering display EOTF transfer characteristics is implemented in the display and the
signal produced by the camera is dependent to the mastering display.
• That means that there is additional processing and metadata are required to convert the signal for a
particular screen.
55

PQ End to End Chain + Metadata
𝑬 𝑬′
𝑭𝑫
Non linear color value, encoded
in PQ space in the range [0,1].
by scene linear light, scaled by
camera exposure in the range [0:1]. The luminance of a displayed linear
component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫.
Scene
Light
OOTF
PQ
Display-referred
Image Data
PQ OETF
PQ
EOTF
Display
Light
Decoding
Camera
Encoding
Mastering Display
E = {𝑹𝒔, 𝑮𝒔, 𝑩𝒔, 𝒀𝒔, or 𝑰𝒔}: The signal determined by scene linear light and scaled by camera exposure in the range [0:1].
E’= {R', G', B'} or { L', M', S'}: A non-linear PQ encoded color value in PQ space in the range [0,1].
𝑭𝑫: The luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫, in cd/m².
• The luminance of a single colour component (𝑅𝐷, 𝐺𝐷, 𝐵𝐷), means the luminance of an equivalent achromatic signal
with all three colour components having that same value.
56

𝑬 𝑬′
camera exposure in the range [0:1].
Scene
Light
OOTF
Display-referred
Image Data
PQ OETF
PQ
EOTF
Display
Light
Decoding
Camera
Encoding
Mastering Display
Display
Light
Display Adjustment
Other Display and Environments
OOTF
Adjust
PQ
EOTF
Decoding
Optional
Metadata
PQ
Metadata is needed for
display adjustment
The luminance of a displayed linear
𝑭𝑫
57

 
 
  1
2
2
1
1
3
2
1
1
0
,
max
10000
EOTF
m
m
m
D
E
c
c
c
E
Y
Y
E
F
















Parameter Values
Input signal to PQ electro-optical transfer
function (EOTF)
𝑬′ : Non-linear PQ encoded value.
The EOTF maps the non-linear PQ signal into display light.
Reference PQ EOTF 4a
(Note 4a – This same non-linearity (and its
inverse) should be used when it is necessary to
convert between the non-linear representation
and the linear representations.)
(Note 4b – In this Recommendation, when
referring to the luminance of a single colour
component (𝑅𝐷, 𝐺𝐷, 𝐵𝐷), it means the luminance
of an equivalent achromatic signal with all three
colour components having that same value.)
where:
𝑬′ (video level) denotes a non-linear colour value {𝑹′, 𝑮′, 𝑩′} or { 𝑳′, 𝑴′, 𝑺′} in PQ space in the range [0:1]
𝑭𝑫 is the luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫, in cd/m². 4b
𝒀 denotes the normalized linear colour value, in the range [0:1] (Y=1 correspond to 𝑭𝑫=10000 nits)
𝑚1 = 2610/16384 = 0.1593017578125
𝑚2 = 2523/4096 × 128 = 78.84375
𝑐1 = 3424/4096 = 0.8359375 = 𝑐3 − 𝑐2 + 1
𝑐2 = 2413/4096 × 32 = 18.8515625
𝑐3 = 2392/4096 × 32 = 18.6875
Reference PQ EOTF, PQ OETF and PQ OOTF
𝑭𝑫
PQ
EOTF
Display
Light
Decoding
𝑬′
𝐹𝐷=EOTF[𝐸′
]=10000 Y
𝑌 =
max ሖ
𝐸
1
𝑚2 − 𝑐1 , 0
𝑐2 − 𝑐3
ሖ
𝐸
1
𝑚2
1
𝑚1
58

Parameter Values
Input signal to PQ opto-electronic
transfer function (OETF)
𝑬: Scene linear light.
The OETF maps relative scene linear light into the non-linear PQ signal value.
Reference PQ OETF
Use of this OETF will yield the reference
OOTF when displayed on a reference
monitor employing the reference EOTF.
Where
𝑬′ is the resulting non-linear signal (𝑹′, 𝑮′, 𝑩′) in the range [0:1]
𝑭𝑫 and 𝑬 are as specified in the opto-optical transfer function
𝑚1, 𝑚2, 𝑐1, 𝑐2, 𝑐3 are as specified in the electro-optical transfer function.
𝐸′
= OETF[E] = EOTF−1
[OOTF[E]] = EOTF−1
[𝐹𝐷]
𝑭𝑫
PQ
EOTF
Display
Light
Decoding
Mastering Display
𝑬 𝑬′
OOTF
PQ
PQ OETF
Encoding
Scene
Light
𝐸𝑂𝑇𝐹−1
𝐹𝐷 =
𝑐1 + 𝑐2𝑌𝑚1
1 + 𝑐3𝑌𝑚1
𝑚2
𝑌 = 𝐹𝐷/10000
59

Parameter Values
Input signal to PQ opto-optical transfer
function (OOTF)
𝑬: Scene linear light.
The OOTF maps relative scene linear light to display linear light.
Reference PQ OOTF
(Note 4c – The mapping of the camera
sensor signal output to 𝐸 may be
chosen to achieve the desired
brightness of the scene.)
where:
𝑬 = {𝑹𝒔, 𝑮𝒔, 𝑩𝒔, 𝒀𝒔, or 𝑰𝒔} is the signal determined by scene light and scaled by camera exposure
The values 𝑬 = {𝑹𝒔, 𝑮𝒔, 𝑩𝒔, 𝒀𝒔, or 𝑰𝒔} are in the range [0:1] 4c
𝑭𝑫 is the luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} or 𝒀𝑫 or 𝑰𝑫, in cd/m².
𝑬′ is a non-linear representation of 𝑬
FD = G1886[E'] = 100 E′ 2.4
FD = OOTF[E] = G1886 [G709[E]]
FD = G1886 [G709[E]] = G1886 E′
𝐸′
= 𝐺709 𝐸 = ቊ1.099(59.5208𝐸)0.45 − 0.099 0.0003024 < 𝐸 < 1
267.84𝐸 0 < 𝐸 < 0.0003024
FD = OOTF[E] = G1886 [G709[E]] =G1886 [E′] = 100𝐸′2.4
E:
OOTF[E] = G1886 [G709[E]]
𝑭𝑫
PQ
EOTF
Display
Light
Decoding
Mastering Display
𝑬 𝑬′
OOTF
PQ
PQ OETF
Encoding
Scene
Light
60

4 129 254 379 504 629 754 879 1019
1000
900
800
700
600
500
400
300
200
100
0
SMPTE ST 2084
𝐜𝐝/𝐦𝟐
PQ 1K EOTF
10 Bit Code Value
4 129 254 379 504 629 754 879 1019
4000
3600
3200
2800
2400
2000
1600
1200
800
400
0
SMPTE ST 2084
𝐜𝐝/𝐦𝟐
PQ 4K EOTF
10 Bit Code Value
Display-referred
Image Data
Display Peak Luminance= 1000 nits Display Peak Luminance= 4000 nits
− The PQ curve’s maximum brightness is always mapped to the maximum brightness of the reference display
to ensure the highest fidelity if the reference and consumer display have similar properties.
Display of PQ signals
61

− The content represented by PQ signals:
• may be limited to the expected capabilities of the displays on which they are intended to be viewed
• may be unlimited and represent the full level of highlights captured by the camera
− In practice, monitors may not reach the full extent of the BT.2100 gamut or the 10 000 𝑐𝑑/𝑚2
limit of the PQ
signal, resulting in the possibility that some encoded colours may not be displayable on some monitors.
− Monitors that support PQ may or may not include tone-mapping to bring very high brightness signals down to
the capability of that monitor.
• Some monitors may clip at their peak output capability (e.g. 2000 𝑐𝑑/𝑚2
).
• Some monitors may contain tone mapping that provides a soft-clip.
62

− If the consumer display has a much lower maximum brightness than the reference display:
⇒ then the entire PQ curve cannot be utilized, resulting in greater quantization (loss of brightness resolution),
………which can lead to visible contouring artifacts in bright areas.
− For example,10-bit content mastered on a 10000-nit display would use all 1023 values for the brightness level.
− Currently most content is mastered on 4000-nit displays, which minimizes this problem.
Only 769 values can be viewed, i.e. up to 1000 nits.
Code word 768 is correspond to 1000
nits in 10 bit for PQ10K EOTF
63

In
display,
the
code
words
equate
to
specific
screen
Luminance
Code
words
are
equally
spaced
in
perceived
brightness
over
Luminance
0.005
to
10000
nits.
• The entire PQ curve cannot be utilized
• Only 769 values can be viewed on 1000
nit consumer display.
• Loss of brightness resolution
• Resulting in greater quantization (769
quantized levels is used for 1000 nits in
comparison of a 1000 nits mastered PQ
signal with1024 quantized levels for)
• It can lead to visible contouring artifacts
in bright areas.
10-bit content mastered on a
10000-nit display 10-bit content on a 1000-nit
consumer display
Code Value 1023
Code Value 0
Code Value 768 (1000 nits)
Code Value 0
Display of PQ signals Code word 768 is correspond to
1000 nits in 10 bit for PQ10K EOTF
64

Code words are equally spaced in perceived brightness over this range of luminance.
Equally
Spaced
Code
Words
(10
bits)
𝑭𝑫: Display Luminance
65

− For Production Use:
• Monitors should generally perform a hard clip to the display capabilities
• Monitors should provide a means to identify pixels that are outside the display’s capability (either in
brightness or colour)
− Care should be taken for any content that is allowed to go outside the reference monitor colour gamut or
dynamic range as that would not have been accurately presented to the operator and cannot be trusted as
part of the approved or intended appearance.
− Reference monitors could provide a selectable overall brightness-attenuation in order to temporarily bring
high brightness signals down to be within the display capability in order to provide a check on any content
encoded brighter than the capability of the reference display.
If a soft-clip is desired, a Look-up-table (LUT) can be
applied to the signal to provide any desired tone mapping.
Display Peak Luminance
500 nits
Display Peak Luminance
10000 nits
Content encoded
brighter than the
capability of the
reference display.
66

1D LUT
− For each input value, there is one and one only output value; interesting but less than useful for video, where
we are almost always dealing with at least three values for Red, Green and Blue.
− 1D LUTs have a 1:1 correspondence between the bit-depth and the number of entries.
− A basic type of LUT for video is three 1D LUTs, one for each color channel.
− 1D LUTs are useful for adjusting contrast and gamma per color channel.
− There is no interaction between color channels.
− As an example a 3X (three channels) 1D LUT could be like this:
R, G, B
3, 0, 0
5, 2, 1
9, 9, 9
− LUTs consist of long lists of these sets of numbers. This means that:
• For input R=G=B=0, the output is R=3, G=0, B=0.
• A 1D LUT has separate tables for each color
channel, however for imaging purpose, it is
almost always three 1D LUTs; one for each color
channel.
• The values of 0 to 255 are the digital color values.
R=G=B=1
R=G=B=0
R=G=B=3
⇒
⇒
⇒
67

3D LUT
− A 3D LUT is more complex but also allows for more control of the image.
− 3D LUTs are useful for converting from one color space to another.
• 3D LUTs use a more sophisticated method of mapping color values from different color spaces.
− It applies a transformation to each value of a color cube in RGB space.
− A 3D LUT provides a way to represent arbitrary color space transformations, as opposed to the 1D LUT where a
value of the output color is determined only from the corresponding value of the input color.
The color cube of an unaffected image.
The same image with a LUT applied.
The cube diagram shows how the
colors are shifted by the LUT.
A 3D LUT is a cube or lattice. The values
of 0 to 255 are the digital color values.
68

3D LUT
− A 3D LUT allows for cross-talk between color channels:
• A component of the output color is computed from all components of the input color providing the 3D
LUT tool with more power and flexibility than the 1D LUT tool.
− Because it would be impossibly large to include every single value for each channel, the number of nodes is
limited.
• With 𝟏𝟕 coordinates per axis (a typical size) there are 𝟏𝟕 × 𝟏𝟕 × 𝟏𝟕 = 𝟒, 𝟗𝟏𝟑 nodes total.
• With 𝟐𝟓𝟕 coordinates per axis there are 𝟐𝟓𝟕 × 𝟐𝟓𝟕 × 𝟐𝟓𝟕 = 𝟏𝟔, 𝟗𝟕𝟒, 𝟓𝟗𝟑 nodes total.
− For this reason, only nodes are precisely calculated; between nodes, the value is interpolated, meaning it is
less precise.
R
G
B
⇒ R’
R
G
B
⇒ G’
R
G
B
⇒ B’
69

3D LUT
− While 1D LUTs are useful for adjusting contrast and gamma per color channel, 3D LUTs are usually more
flexible.
− 3D LUTs can
• cross-convert colors between channels
• alter saturation
• independently control saturation, brightness, and contrast
− 3D LUTS must be interpolated from a subset or the LUT could be over a gigabyte in size.
− 3D LUTs can be integer values or floating point.
• 𝟖 × 𝟖 × 𝟖 = 𝟓𝟏𝟐 nodes ⇒ too small for most transforms
• 𝟏𝟔 × 𝟏𝟔 × 𝟏𝟔 = 𝟒𝟎𝟗𝟔 nodes ⇒ a reasonable size for preview
• 𝟔𝟒 × 𝟔𝟒 × 𝟔𝟒 = 𝟐𝟔𝟐𝟏𝟒𝟒 nodes ⇒ a rendering quality
70

− If the BT.2100 PQ signal is presented to a monitor that expects a Recommendation ITU-R BT.709 (BT.709) input:
• Image will appear dim and washed out
• Colours will be desaturated
• There will be some hue shifts
PQ HDR Signal
SDR BT.709 Display
HDR Monitor (4K, PQ) SDR Monitor (HD, PQ)
71

− An external 3D LUT can provide the down-mapping function necessary to bring both colour and brightness
into the BT.709 colour volume, thus allowing satisfactory display on the legacy BT.709 monitor.
− Some monitors may provide this function by means of an internally provided 3D LUT.
• While this allows viewing on the BT.709 monitor, the resulting images should not be used to make critical
judgements of the HDR production.
− If PQ signals must be monitored in an environment brighter than the reference environment (5 𝑐𝑑/𝑚2
surround), manufacturers may provide modified brightness and display characteristics intended to
compensate for the different viewing environment.
PQ HDR Signal
SDR BT.709 Display
HDR Monitor (4K, PQ) SDR Monitor (HD, PQ)
3D LUT
72

SMPTE
2084
PQ
Look
Up
Tables
Linear Ramp Test Signal BT.709
Look Up Table SMPTE 2084 1000nits
Reference White 100nits
Look Up Table SMPTE 2084 1000nits
Reference White 300nits
73
Using Look Up Tables (LUTs) In Post Production
2084 HDR (PQ) 0% 2 % 18% 90%
100
%
BT.709 100nits 0 9 41 95 100
HDR 1000nits 0 37 58 75 76
Camera-Side Conversion BT.709 (SDR) to PQ1K

600 cd/m² “shading”
e.g. OB truck
e.g. studio gallery
e.g. Code Values 81 - 674
2000 cd/m² “grade”
Display
Re-mapping
e.g. Code Values 74 –636
e.g. Code Values 81 -728
• The signal varies with mastering display.
• Display re-mapping often required.
PQ Represents Absolute Brightness
Display
Re-mapping
Display
Re-mapping
Display
Re-mapping
e.g. 400 cd/m², home theatre
e.g. 1000 cd/m², evening viewing
e.g. 2000 cd/m², daytime viewing
e.g. 4000 cd/m², signage display
74

75
Difference between PQ-BT2100 and PQ-ST2084
− Dolby's perceptual quantizer (PQ) has been standardized as SMPTE ST-2084 as EOTF and OETF.
− In this standardization the OETF is considered to be the exact inverse of the EOTF, resulting in a linear
OOTF, i.e. no reference OOTF is applied.
− In addition, PQ is based on an SMPTE and Dolby subject study to determine audience preference over
the required dynamic range. Since the study showed that viewers prefer a luminance range between
0.001 cd/m² and 10,000 cd/m², the standard covers exactly this dynamic range.

76
Difference between PQ-BT2100 and PQ-ST2084
− ITU-R BT.2100, specifies PQ as a 10-bit EOTF and OETF, but in combination with a reference OOTF.
− The OOTF being considered in the camera (or being imposed in the production process), makes PQ a
display-related system that is initially designed to provide an intended image impression in a BT.2100
defined reference environment (5 nits or cd/m² around the monitor while avoiding scattered light on the
display). If this reference condition is not fulfilled, the viewer will get a wrong impression of the image.
− Therefore, PQ as an absolute brightness metric basically ensures that an image is reproduced on all
systems with the same absolute luminance, which ensures good comparability.

77
Relevant Cases of PQ and HLG Looks

Human Eye Sensitivity and Dynamic Range
Highlights
• The human eye is less sensitive to changes in brightness for
bright areas of a scene.
• Not so much dynamic range is required for these areas and
they can be compressed without reducing display quality.
Mid-tones
• The human eye is reasonably sensitive to
changes in mid-tone brightness.
Low-lights
• The human eye is more sensitive to changes in
brightness in darker areas of a scene and plenty of
dynamic range is needed to record these areas well.
Eye
Sensitivity
Scene Brightness
Less
Dynamic
Range
More
Dynamic
Range
∆𝑰
𝑰
79

Eye
Sensitivity
Scene Brightness
Less
Dynamic
Range
More
Dynamic
Range
• For much brighter specular highlights, do not need as
many code words to represent them (large L).
• In the darker areas of a picture (small L), minor changes
can be seen much more than in brighter areas of a
picture (small ∆L is detectable). So more code words
should be given to the darker areas.
• The eye needs more dynamic range in low light
levels than in high light levels
• More Code Words or More Bits
Minimum Detectable Contrast (%) =
𝐌𝐢𝐧𝐢𝐦𝐮𝐦 𝐃𝐞𝐭𝐞𝐜𝐭𝐚𝐛𝐥𝐞 𝐃𝐢𝐟𝐟𝐞𝐫𝐞𝐧𝐜𝐞 𝐢𝐧 𝐋𝐮𝐦𝐢𝐧𝐚𝐧𝐜𝐞
𝐁𝐚𝐜𝐤𝐠𝐫𝐨𝐮𝐧𝐝 𝐋𝐮𝐦𝐢𝐧𝐮𝐧𝐜𝐞 𝐋𝐞𝐯𝐞𝐥
× 𝟏𝟎𝟎
For a constant number of bits (ex, 10 bits codes), we need to give more code words to the lower light levels than bright areas to improve how we see the blacks.
=
∆𝑳
𝑳
×100
80

− Linear sampling wastes codes
values where they do little good.
− Log encoding distributes codes
values more evenly — in a way
that more closely conforms to
how human perception works.
Eye
Sensitivity
Scene Luminance
Eye
Sensitivity
Scene Luminance
Steep perceptual slope means
high gain to blacks
Eye
Sensitivity
Scene Brightness
Perceptual
Quantizer (PQ)
Perception is 1/3 power-law
“cube-root”
81

Contouring
(Banding)
BT. 1886 Performance in 10-Bit, 15-Bit and 13-Bit Log
Optical
Electronic
OETF
(Camera Gamma)
avoiding banding effect? Gamma: Wasted bits in bright regions
Log: Wasted bits in dark regions
Above Threshold
Below Threshold
Minimum
Contrast
Step
(%)
Luminance in nits (𝒄/𝒎𝟐)
∆𝑳
𝑳
×
100
82

Optical
Electronic
OETF
(Camera Gamma)
PQ EOTF on Barten Ramp
Gamma: Wasted bits in bright regions
Log: Wasted bits in dark regions
Above Threshold
Below Threshold
Contouring
(Banding)
Luminance in nits (𝒄/𝒎𝟐)
Minimum
Contrast
Step
(%)
∆𝑳
𝑳
×
100
83

Contrast Sensitivity
– This graph is redrawn from Schreiber’s Fundamentals of Electronic Imaging Systems.
At very low luminance values, the curve departs from logarithmic
behaviour and approximates a square-root; this characteristic is
called the de Vries-Rose law (Hessel de Vries, Albert Rose).
The flat portion of the curve shows that the
perceptual response to luminance – termed
lightness – is approximately logarithmic.
∆𝑳
𝑳
= 𝑪 ≈ 𝟎. 𝟎𝟐
Slope=0.5
The transition occurs between absolute
luminance values of 0.1 to 1 nt.
(0.025)
(0.0158)
(0.039)
(0.063)
(0.1)
(0.158)
(
∆𝑳
𝑳
)
∆𝑳
𝑳
= 𝑲
Over a range of luminance values of about
300:1, the discrimination threshold of vision is
approximately a constant ratio of luminance. 𝑺 =
𝟏
𝑪𝒎𝒊𝒏
𝑪𝒎𝒊𝒏 =
∆𝑳𝒎𝒊𝒏
𝑳
84

HLG OETF Facts
1
0.8
0.6
0.4
0.2
0
Video Signal
Relative Sensor Output
0 0.5 1 1.5 2 2.5 3
ConventionalSDR CameraCurve
In the low lights it becomes increasingly difficult to perceive banding. That is, the
threshold of visibility for banding becomes higher as the image gets darker. It
means for small values of 𝑳, with decreasing the 𝑳, ∆𝑳 is increased.
• So an ideal OETF would be a gamma law in the low lights because it has
invisible quantization distortion because of higher threshold for visibility of
banding or contouring.
De Vries-Rose law
𝑳 ↓ ∆𝑳 𝒊𝒔 𝒎𝒐𝒓𝒆 𝒑𝒆𝒓𝒄𝒆𝒏𝒕𝒂𝒈𝒆 𝒐𝒇 𝑳
⇒
De Vries-Rose Law
85

HLG OETF Facts
1
0.8
0.6
0.4
0.2
0
Video Signal
0 0.5 1 1.5 2 2.5 3
Camera LogCurve
In the brighter parts and highlights of an image the threshold for
perceiving quantization error (banding or contouring) is approximately
constant, so quantization distortion visibility is constant.
• This implies a logarithmic OETF would provide the maximum
dynamic range for a given bit depth.
Weber’s law
Weber–Fechner Law
86

HLG OETF Facts
1
0.8
0.6
0.4
0.2
0
Video Signal
0 0.5 1 1.5 2 2.5 3
Best ofBoth
87

1
0.8
0.6
0.4
0.2
0
Video Signal
0 0.5 1 1.5 2 2.5 3
HLG HDR Camera Curve
Ideal OETF
An ideal OETF might be logarithmic in the high tones and a gamma law in
the low lights, which is essentially the form of the hybrid log-gamma OETF.
HLG OETF Facts
88

Conventional SDR CameraCurve
Video
Signal
Camera Log Curve
Video
Signal
Best of both should be selected.
Video
Signal
Hybrid Log Gamma HDR Camera Curve
Video
Signal Relative Sensor Output
HLG OETF Facts
In the low lights it becomes increasingly difficult to perceive
banding. That is, the threshold of visibility for banding
becomes higher as the image gets darker.
• So an ideal OETF would be a gamma law in the low
lights because it has invisible quantization distortion
because of higher threshold for visibility of banding
or contouring.
In the brighter parts and highlights of an image the
threshold for perceiving quantization error (banding or
contouring) is approximately constant, so quantization
distortion visibility is constant.
• This implies a logarithmic OETF would provide
the maximum dynamic range for a given bit
depth.
Weber’s law
De Vries-Rose law
0 0.5 1 1.2 2 2.5 3 0 0.5 1 1.2 2 2.5 3
0 0.5 1 1.2 2 2.5 3
0 0.5 1 1.2 2 2.5 3
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
An ideal OETF might be logarithmic in the high tones
and a gamma law in the low lights, which is essentially
the form of the hybrid log-gamma OETF.
Ideal OETF
89

HLG OETF Facts
Knee
– The knee characteristic compresses the image highlights to prevent the signal from clipping or being “blown out”
(overexposed) and so extend the dynamic range of the signal
Weber’s law
– In the brighter parts and highlights of an image the threshold for perceiving quantization error (banding or contouring)
is approximately constant, so quantization distortion visibility is constant.
• This implies a logarithmic OETF would provide the maximum dynamic range for a given bit depth.
De Vries-Rose law
– Proprietary logarithmic OETFs are in widespread use. But in the low lights it becomes increasingly difficult to perceive
banding. That is, the threshold of visibility for banding becomes higher as the image gets darker.
– The conventional gamma OETF used for SDR comes close to matching the De Vries-Rose law, which is perhaps not
coincidental since gamma curves were designed for dim CRT displays.
• So an ideal OETF would be a gamma law in the low lights because it has invisible quantization distortion because
of higher threshold for visibility of banding or contouring.
.
So an ideal OETF might be logarithmic in the high tones and a gamma law in the low
lights, which is essentially the form of the hybrid log-gamma OETF. 90

Hybrid Log-Gamma (HLG) HDR-TV OETF
Standardized as ARIB STB-B67 and ITU-R BT.2100
a = 0.17883277
b = 0.28466892
c = 0.55991073
𝑬′
= 𝑶𝑬𝑻𝑭 𝑬 =
𝟑𝑬 𝟎 ≤ 𝑬 ≤
𝟏
𝟏𝟐
𝒂. 𝒍𝒏 𝟏𝟐𝑬 − 𝒃 + 𝒄
𝟏
𝟏𝟐
< 𝑬 ≤ 𝟏
a = 0.17883277, b = 0.28466892, c = 0.55991073
Linear Scene Light
Signal
Level
SDR OETF
SDR with Knee
HDR HLG OETF
Knee point: 87.5% signal level
Reflectance Object or Reference
(Luminance Factor, %)
Nominal Signal
Level (%)
Grey Card (18% Reflectance) 42.5
Reference or Diffuse White (100%
Reflectance)
79
A notional SDR “knee” is shown on the same plot, with
a breakpoint of 87.5% signal level, which extends the
SDR dynamic capture range substantially.
SDR OETF
SDR with Knee
HDR HLG OETF
E (Scene Light) : signal for each colour component {Rs, Gs, Bs} proportional to scene linear light and scaled by
camera exposure, normalized to the range [0:1]
E′ (Video Level): The resulting non-linear signal {R′, G′, B′} in the range [0:1].
ITU-R Application 2 ,ARIB B67 (Association of Radio Industries and Businesses)
HLG can capture
nearly a factor of 3
more luminance than
100% reflectivity.
91

Standardized as ARIB STB-B67 and ITU-R BT.2100
a = 0.17883277
b = 0.28466892
c = 0.55991073
𝑬′
𝟑𝑬 𝟎 ≤ 𝑬 ≤
𝟏
𝟏𝟐
𝒂. 𝒍𝒏 𝟏𝟐𝑬 − 𝒃 + 𝒄
𝟏
𝟏𝟐
< 𝑬 ≤ 𝟏
E (Scene Light) : signal for each colour component {Rs, Gs, Bs} proportional to scene linear light and scaled by
camera exposure, normalized to the range [0:1]
E′ (Video Level): The resulting non-linear signal {R′, G′, B′} in the range [0:1].
a = 0.17883277, b = 0.28466892, c = 0.55991073
Linear Scene Light
Signal
Level
SDR OETF
SDR with Knee
HDR HLG OETF
Knee point: 87.5% signal level
More
Code
Words
for
Dark
Area
Less
Code
Words
for
Bright
Area
A notional SDR “knee” is shown on the same plot, with
a breakpoint of 87.5% signal level, which extends the
SDR dynamic capture range substantially.
Nominal Signal
Level (%)
Grey Card (18% Reflectance) 42.5
Reference or Diffuse White (100%
Reflectance)
79
SDR OETF
SDR with Knee
HDR HLG OETF
ITU-R Application 2 ,ARIB B67 (Association of Radio Industries and Businesses)
HLG can capture
nearly a factor of 3
more luminance than
100% reflectivity.
92

93

More Code Words
for Dark Area
Less Code Words for
Bright Area
94

Code Words Utilization by Luminance Range, Gamma 2.4
Too many code words allocated
to very bright regions and not
enough allocated to dark regions.
95

– These plots assume that two cameras, one Recommendation ITU-R BT.2020 and the other BT.2100 (that is,
one SDR and one HDR), are set up with the same sensitivity.
– The 18% grey may be useful when trying to match SDR and HDR cameras as the 18% grey should not be
affected by any SDR camera “knee”.
• E.g. if both cameras were looking at the same 18% grey chart, then their sensitivities (gain, iris, and shutter
time) could be adjusted so that the signal level was 42.5% of nominal full signal level for both cameras.
• Setting 18% grey to 42.5% results in the diffuse white signal level being 100% for SDR, and 79% for HLG.
SDR ITU-R BT.2020
HDR ITU-R BT.2100
18% Grey Chart
Nominal Full Signal Level
42.5%
42.5%
100%
79%
100% Grey Chart
96

− Above 50% signal level the HDR OETF is logarithmic, which means it can capture higher light levels (such
as specular reflections and highlights) without clipping.
− When the two cameras’ (SDR and HDR) sensitivities are equalized:
• For signal levels at.or below 50% both the SDR (BT.2020) and HDR responses to light amplitude would
be almost the same.
Reflectance Object or
Reference
Nominal
Signal Level
(SDR%)
Nominal
Signal Level
(HLG%)
Grey Card (18%
Reflectance)
42.5 42.5
Reference or Diffuse White
(100% Reflectance)
100 79
SDR OETF
SDR with Knee
HDR HLG OETF
97

𝐕 = 𝟏. 𝟎𝟗𝟗𝑳𝟎.𝟒𝟓
− 𝟎. 𝟎𝟗𝟗 0.018 < L <1
𝐕 = 𝟒. 𝟓𝟎𝟎𝑳 0 < L < 0.018
𝑬′
𝟑𝑬 𝟎 ≤ 𝑬 ≤
𝟏
𝟏𝟐
𝒂. 𝒍𝒏 𝟏𝟐𝑬 − 𝒃 + 𝒄
𝟏
𝟏𝟐
< 𝑬 ≤ 𝟏
HLG OETF
0.2
0.18
0.16
0.14
0.12
0.1
0.08
0.06
0.04
0.02
0
0 0.01 0.05
Video
Signal
0.02 0.03 0.04
HLG
BT.709
SDR OETF
– There are small differences between the two plots below 50% of nominal signal range.
– This is because SDR OETFs include a linear portion near black (𝐕 = 𝟒. 𝟓𝟎𝟎𝑳) to avoid excessive noise
amplification. HLG, by contrast, uses a pure square root OETF at low levels ( 𝟑𝑬).
• This allows HLG to achieve higher dynamic range “in the blacks”, but it does mean that camera
manufacturers must use an alternative to the linear part of the SDR OETF to avoid excessive noise
amplification in the black.
98

Preferred Min.
Preferred Max.
(Narrow Range)
(White)
(Black)
(super-whites)
(sub-blacks)
System
Bit Depth
Range in Digital sample (Code) Values
Nominal
Video Range
Preferred
Min./Max.
Total Video
Signal Range
8-bit 16-235 5-246 1-254
10-bit 64-940 20-984 4-1019
12-bit 256-3760 80-3936 16-4079
16-bit 4096-60160 1280-62976 256-65279
Extended
Range
EBU R103: Video Signal Tolerance in Digital Television Systems
− Television and broadcasting
do not primarily use the “full
range” of digital sample
(code) values available in a
given format.
− Another term, “extended
range” is not formally defined
but is sometimes used for the
range 64 – 1019 (10-bit), so
including super-whites, whilst
maintaining sub-blacks.
− SDI always reserves some
code values for its own signal
processing requirements.
99
This percentage are used just in narrow range.

Preferred Min.
Preferred Max.
(Narrow Range)
(White)
(Black)
(super-whites)
(sub-blacks)
System
Bit Depth
Range in Digital sample (Code) Values
Nominal
Video Range
Preferred
Min./Max.
Total Video
Signal Range
8-bit 16-235 5-246 1-254
10-bit 64-940 20-984 4-1019
12-bit 256-3760 80-3936 16-4079
16-bit 4096-60160 1280-62976 256-65279
Extended
Range
− Often “Narrow Range” or
“Video Range” is used in
television and
broadcasting.
− Narrow range signals
• may extend below black
(sub-blacks)
• may exceed the nominal
peak values (super-
whites)
• should not exceed the
video data range.
100
This percentage are used just in narrow range.

Video Signal
− In a video signal, each primary component should lie between 0 and 100% of the Narrow Range (Video Range) between
black level and the nominal peak level (R and G and B).
Video Signal Tolerance
− The EBU recommends that, the RGB components and the corresponding Luminance (Y) signal should not normally exceed
the “Preferred Minimum/Maximum” range of digital sample levels.
− Any signals outside the “Preferred Minimum/Maximum” range are described as having a gamut error or as being “Out-of-
Gamut”.
− Signals shall not exceed the “Total Video Signal Range”, overshoots that attempt to “exceed” these values may clip.
System Bit Depth Range in Digital sample (Code) Values
Nominal Video Range Preferred Min./Max. Total Video Signal Range
8-bit 16-235 5-246 1-254
10-bit 64-940 20-984 4-1019
12-bit 256-3760 80-3936 16-4079
16-bit 4096-60160 1280-62976 256-65279
101

– Note that the conventional ‘narrow range’ digital signal can actually support signal levels of up to 109% of
nominal full scale.
• This is to accommodate overshoots and highlights.
– If this additional signal range is used (though not all equipment supports it) then even higher light levels
may be captured without clipping.
Preferred Max.
(Narrow Range)
(White)
(super-whites)
102

– Considering a nominal full scale signal (i.e. 100% signal level), and with the cameras set up as mentioned
(When the two cameras’ (SDR and HDR) sensitivities are equalized):
– If the signal is not allowed to excurse to the maximum 100% signal range then:
⇒ The SDR camera can capture objects no brighter than 100% reflective (i.e. no highlights).
⇒ The HLG camera increases the luminance that can be captured by a factor of 3.
SDR ITU-R BT.2020
HDR ITU-R BT.2100
42.5%
42.5%
100%
100%
Luminance Equivalent to 300% Reflectivity
(“3 times more than diffuse white” )
18% Grey Chart
(“diffuse white” )
103

– Considering a nominal full scale signal (i.e. 100% signal level), and with the cameras set up as mentioned
(When the two cameras’ (SDR and HDR) sensitivities are equalized):
– If the signal is allowed to excurse to the maximum 109% range (super-whites) then:
⇒ SDR can capture luminance equivalent to 120% reflectivity
⇒ HLG can capture nearly a factor of 5 more luminance than 100% reflectivity
SDR ITU-R BT.2020
HDR ITU-R BT.2100
42.5%
42.5%
100%
100%
(“1.2 times more than diffuse white” )
(“5 times more than diffuse white” )
18% Grey Chart
104

– A native interpretation of these plots might suggest that the dynamic range of HLG is only 3 times greater
than SDR, but this is not the case because:
I. HDR is about more than just increasing the brightness of highlights.
 Creating the detail in “lowlights” and “in the black” is also very important and HLG adds much
dynamic range here.
II. The OETF describes the capture dynamic range. The dynamic range on the display is greater
because of overall system gamma.
 The OOTF maps relative scene linear light to display linear light.
 With a typical system gamma of 1.2, and the camera sensitivity adjusted as described, HLG
supports display highlights which are a factor of 3.7 (or 6.9 with super-whites) higher than diffuse
white.
31.2
= 3.7
51.2
= 6.9
𝑬𝒊𝒏
OOTF
𝑬𝒐𝒖𝒕
𝑬𝒐𝒖𝒕 = 𝑬𝒊𝒏
𝛾𝒔𝒚𝒔𝒕𝒆𝒎
105

– The foregoing discussion assumes that “diffuse white” produces 100% signal output for SDR cameras.
– Whilst this may be true for some programmes, the signal level for diffuse white is not defined for SDR signals.
• In practice diffuse white varies between about 90% and 115% depending on genre, geographical
region, and artistic preference.
• Drama, in particular, tends to set diffuse white at a lower signal level.
 This supports more artistically pleasing pictures that can contain some highlight detail.
– HLG supports a much greater dynamic range than SDR, and can take advantage of this by setting diffuse
white at a lower signal level to support more highlight dynamic range.
106

Report ITU-R BT.2408:
− For HLG HDR, diffuse white should be
set at a signal level of 75%.
− It configured by making the output
from an 18% grey card correspond to
a signal level of 38%, rather than the
42.5%.
– Setting 18% grey to 38% results in the
diffuse white signal level being 89% for
SDR, and 75% for HLG.
Nominal Signal Level
(HLG %)
Grey Card (18% Reflectance) 38
Reference or Diffuse White (100% Reflectance) 75
18% grey card correspond to a signal level of
38% and diffuse white at a signal level of 75%.
18% grey card correspond to a signal level of
42.5%, diffuse white at a signal level of 79%.
Report ITU-R BT.2408
With slightly lower signal level for diffuse white, the
dynamic range available for highlights is increased.
SDR ITU-R BT.2020
HDR ITU-R BT.2100
18% Grey Chart
38%
38%
89%
75%
100% Grey Chart
107

– If the signal is not allowed to excurse to the maximum 100% signal range then SDR can now support scene
luminance equivalent to 125% of diffuse white, and HDR can support scene luminance of 375% diffuse
white.
SDR ITU-R BT.2020
HDR ITU-R BT.2100
38%
38%
100%
100%
18% Grey Chart
108

– These figures increase to 150% and about 620% if super-whites (109% signal range) are used.
• So the use of super-whites is much more advantageous for HLG than it is for SDR.
SDR ITU-R BT.2020
HDR ITU-R BT.2100
38%
38%
100%
100%
(“1. 5 times more than diffuse white” )
18% Grey Chart
Preferred Max.
(Narrow Range)
(White)
(super-whites)
109

– Note that these figures increase further to 163% and 890% at the display when a typical system gamma of
1.2 is used.
1.51.2
= 1.63
6.21.2
= 8.9
SDR ITU-R BT.2020
HDR ITU-R BT.2100
38%
38%
100%
100%
(“1. 5 times more than diffuse white” )
𝑬𝒊𝒏
OOTF
𝑬𝒐𝒖𝒕
𝑬𝒐𝒖𝒕 = 𝑬𝒊𝒏
𝛾𝒔
110

Reference Viewing Environment for Critical Viewing of HDR
Parameter Parameter Value
Surround and Periphery 3a Neutral grey at D65
Luminance of Surround 5 nits
Luminance of Periphery ≤ 5 nits
Ambient Lighting Avoid light falling on the screen
Viewing Distance 3b
For 1920 ×1080 format: 3.2 picture heights
For 3840 ×2160 format: 1.6 to 3.2 picture heights
For 7680 ×4320 format: 0.8 to 3.2 picture heights
Peak Luminance of Display 3c ≥ 1 000 nits
Minimum Luminance of Display (Black Level) 3d ≤ 0.005 nits
Note 3a – “Surround” is the area surrounding a display that can affect the adaptation of the eye, typically the wall or curtain
behind the display; “Periphery” is the remaining environment outside of the surround.
Note 3b – When picture evaluation involves resolution, the lower value of viewing distance should be used. When resolution
is not being evaluated, any viewing distance in the indicated range may be used.
Note 3c – This is not to imply this level of luminance must be achieved for full screen white, rather for small area highlights.
Note 3d – For PQ in a non-reference viewing environment, or for HLG (in any viewing environment), the black level should
be adjusted using the PLUGE test signal and procedure specified in Recommendation ITU-R BT.814.
111

− The overall system non-linearity, or “rendering intent” is defined by the opto-optical transfer function, or
OOTF.
− The OOTF maps relative scene linear light to display linear light.
− Rendering intent is needed to compensate for the psychovisual effects of watching an emissive screen in
a dark or dim environment, which affects the adaptation state (and hence the sensitivity) of the eye.
System Gamma
Normalized RGB
R’G’B
𝜸𝑺
(To compensate for the psychovisual effects of watching
an emissive screen in a dark or dim environment)
Output Luminance
112

System Gamma in Cinema:
− Traditionally movies were, and often still are, shot on negative film with a gamma of about 0.6.
− They were then displayed from a print with a gamma of between 2.6 and 3.0.
− This gives movies a system gamma of between 1.6 (0.6×2.6) and 1.8 (0.6×3), which is needed because of
the dark viewing environment.
System Gamma in SDR:
− The SDR TV has an OOTF which is also a gamma curve with a system gamma of 1.2.
System Gamma
113

− Simply applying a gamma curve to each red, green and blue components separately as is done for SDR
television distorts the colour; in particular it distorts saturation but also to a lesser extent the hue.
− Example:
− In this example, the ratio of green to blue and red has increased (from 3:1 to 9:1).
− This means, a green pixel would have appeared as a discernibly different shade of green.
− This approach is far from ideal if it is wished to avoid distorting colours when they are displayed.
The Problem of Appling Gamma to R,G and B Components
Normalized RGB
(0.25, 0.75, 0.25)
R’G’B
(0.0625, 0.5625, 0.0625)
(i.e. squaring the value of the components)
Pixel has got slightly darker
𝜸𝑫 = 𝟐 Gamma Circuit
Gamma Circuit
Gamma Circuit
114

=
OOTF
gamma 1.5
on RGB
Scene Light Display Light
=
30% 90% 95% 78% 16% 85% 93% 71%
• Each production format looks different due to different OOTFs (Hue, Saturation, Tone)
• BT.709/sRGB colour simulation
• OOTF gamma 1.5 to highlight effect
• Traditional OOTF “gamma” on RGB increases colour saturation
Increased
colour
saturation
Gamma Circuit
Gamma Circuit
Gamma Circuit
115

=
=
30% 90% 95% 78% 16% 85% 93% 71%
OOTF
gamma 1.5
on RGB
• BT.709/sRGB colour simulation
• OOTF gamma 1.5 to highlight effect
• Traditional OOTF “gamma” on RGB increases colour saturation
• Scene and Display Light are Different Colours
Increased
colour
saturation
Gamma Circuit
Gamma Circuit
Gamma Circuit
116

=
=
30% 90% 95% 79% 26% 78% 84% 68%
OOTF
gamma 1.5
on Luminance
in HLG
Resultant
colour
saturation
Appling OOTF to Luminance Component to Avoid Colour Changes
• HLG Applies Gamma on Luminance to Preserves Colour Saturation of Original Scene
• Necessary as different peak luminance displays require different gammas
117

− Instead of the current SDR practice of applying a gamma curve independently to each colour
component, for HDR it should be applied to the luminance alone.
− By applying rendering intent (OOTF) to the luminance component only it is possible to avoid colour
changes in the display.
− According to Recommendation ITU-R BT.2100, luminance is given by:
− 𝒀𝒔: normalized linear scene luminance
− 𝑹𝒔, 𝑮𝒔 and 𝑩𝒔: normalized linear scene light (i.e. before applying OETF) colour components signals
𝒀𝒔 = 𝟎. 𝟐𝟔𝟐𝟕𝑹𝒔 + 𝟎. 𝟔𝟕𝟖𝟎𝑮𝒔 + 𝟎. 𝟎𝟓𝟗𝟑𝑩𝒔
HLG OETF HLG EOTF
𝑬: [𝟎,𝟏] 𝑬′: [𝟎,𝟏]
𝑭𝑫
Linear Scene-light
Non-linear
𝑭𝑺
118

− The HLG reference OOTF is therefore given by:
𝑭𝑫: luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, or 𝑩𝑫}, in cd/m²
𝑬: signal for each colour component {𝑹𝑺, 𝑮𝑺, 𝑩𝑺} proportional to scene linear light and scaled by camera
exposure, normalized to the range [0:1].
𝜶 : user adjustment for the luminance of the display, commonly known in the past as a “contrast control”.
• It represents 𝑳𝑾, the nominal peak luminance of a display for achromatic pixels in cd/m².
𝜸 : is an exponent, which varies depending on 𝑳𝑾, and which is equal to 1.2 at the nominal display peak
luminance of 1000 cd/m²
𝒀𝒔 = 𝟎. 𝟐𝟔𝟐𝟕𝑹𝒔 + 𝟎. 𝟔𝟕𝟖𝟎𝑮𝒔 + 𝟎. 𝟎𝟓𝟗𝟑𝑩𝒔
𝑭𝑫 = 𝑶𝑶𝑻𝑭 𝑬 = 𝛂𝒀𝑺
𝜸−𝟏
𝑬
𝑹𝑫 = 𝛂𝒀𝑺
𝜸−𝟏
𝑹𝑺
𝑮𝑫 = 𝛂𝒀𝑺
𝜸−𝟏
𝑮𝑺
𝑩𝑫 = 𝛂𝒀𝑺
𝜸−𝟏
𝑩𝑺
119

Reference OOTF = OETF (HLG) + EOTF (HLG)
HLG OETF HLG EOTF
𝑬: [𝟎, 𝟏] 𝑬′
: [𝟎, 𝟏]
𝑭𝑫
Linear Scene-light
Non-linear
𝑭𝑺
120

HLG OETF HLG EOTF
𝑬: [𝟎, 𝟏] 𝑬′
: [𝟎, 𝟏]
Linear Scene-light
Non-linear
Non linear color value,
encoded in PQ space in
the range [0,1].
The signal determined by scene
linear light, scaled by camera
exposure in the range [0:1].
𝑭𝑫 :The luminance of a displayed linear
component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫} in cd/m².
The luminance of a single colour component (𝑹𝑫, 𝑮𝑫,
𝑩𝑫 ), means the luminance of an equivalent
achromatic signal with all three colour components
having that same value.
𝑭𝑫
𝑭𝑺
121

Cancel
(seasoning)
OETF-1 OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
EOTF
Optical Signal
Scene Light
Electronic Signal
OETF
OOTF Position in HLG
Scene-Referred Signal
Linear Scene Light
Output [%]
Input [cd/㎡ ]
122

Cancel
(seasoning)
OETF-1 OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
EOTF
Optical Signal
Scene Light
Electronic Signal
OETF
Linear Scene Light
Output [%]
Input [cd/㎡ ]
The HLG system specifies a scene-referred HDR signal which means that every pixel value in the image
represents the light intensity in the captured scene.
• Therefore, the transfer characteristics can be implemented directly in the camera and the signal
produced by the camera is independent of the display.
• That means that there is no additional processing and no metadata are required to convert the signal
for a particular screen.
123

HLG End to End Chain
𝑬
𝑭𝑫
in HLG space in the range [0,1].
The luminance of a displayed
linear component
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
Reference Display
HLG
O𝐄𝐓𝐅 −𝟏
Decoding
OOTF
HLG EOTF
𝑬′
𝑬 = {𝑹𝒔, 𝑮𝒔, 𝑩𝒔}: The signal determined by scene linear light and scaled by camera exposure in the range [0:1].
𝑬’= {𝑹′, 𝑮′, 𝑩′}: A non-linear PQ encoded color value in PQ space in the range [0,1].
𝑭𝑫: The luminance of a displayed linear component in nits.
The luminance of a single colour component (𝑹𝑫, 𝑮𝑫, 𝑩𝑫), means the luminance of an equivalent achromatic signal with
all three colour components having that same value.
124

𝑬
linear component
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
Reference Display
HLG
Decoding
OOTF
HLG EOTF
𝑬′
𝑭𝑫
linear component
Non-reference
Display Light
Non Reference Display and Environment
HLG
Decoding
OOTF
HLG EOTF
Reference
No Metadata is needed for
display adjustment
𝑬′
Display Adjustment
OOTF
Adjust
𝑭𝑫
Reference
125

Parameter Values
Input signal to HLG OETF
E: Scene linear light signal.
The OETF maps relative scene linear light into the non-linear signal value.
HLG Reference OETF 5a
𝑬 is a signal for each colour component {𝑹𝒔, 𝑮𝒔, 𝑩𝒔} proportional to scene linear light normalized to the range
[0:1]. 5b
𝑬′ is the resulting non-linear signal {𝑹′, 𝑮′, 𝑩′} in the range [0:1].
𝒂 = 𝟎. 𝟏𝟕𝟖𝟖𝟑𝟐𝟕𝟕, 𝒃 = 𝟏 − 𝟒𝒂, 𝒄 = 𝟎. 𝟓 − 𝒂. 𝒍𝒏(𝟒𝒂) 5c
Hybrid Log-Gamma (HLG) System Reference Non-linear Transfer Functions
• Note 5a – The inverse of this non-linearity should be used when it is necessary to convert between the non-linear representation and the linear representation of scene light.
• Note 5b – The mapping of the camera sensor signal output to E may be chosen to achieve the desired brightness of the scene.
• Note 5c – The values of b and c are calculated to b = 0.28466892, c = 0.55991073.
𝑬′ = 𝑶𝑬𝑻𝑭 𝑬 =
𝟑𝑬 𝟎 ≤ 𝑬 ≤
𝟏
𝟏𝟐
𝒂. 𝒍𝒏 𝟏𝟐𝑬 − 𝒃 + 𝒄
𝟏
𝟏𝟐
< 𝑬 ≤ 𝟏
𝑬 𝑬′
𝑭𝑫
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
HLG
Decoding
OOTF
HLG EOTF
126

Parameter Values
HLG Input signal to OOTF
E: Scene linear light signal.
The OOTF maps relative scene linear light to display linear light.
HLG Reference OOTF 5i
𝑭𝑫 is the luminance of a displayed linear component {𝑹𝑫, 𝑮𝑫, 𝑩𝑫}, in 𝒄𝒅/𝒎𝟐. 5d
𝑬 is a signal for each colour component {𝑹𝒔, 𝑮𝒔, 𝑩𝒔} proportional to scene linear light normalized to the range [𝟎: 𝟏].
𝒀𝑺 is the normalized linear scene luminance.
α is the variable for user gain in 𝒄𝒅/𝒎𝟐. It represents 𝑳𝑾, the nominal peak luminance of a display for achromatic pixels.
𝜸 is the system gamma.
𝜸 = 𝟏. 𝟐 at the nominal display peak luminance of 𝟏𝟎𝟎𝟎 𝒄𝒅/𝒎𝟐. 5e, 5f, 5g
𝜸−𝟏
𝑬
𝜸−𝟏
𝑹𝑺
𝜸−𝟏
𝑮𝑺
𝜸−𝟏
𝑩𝑺
𝒀𝒔 = 𝟎. 𝟐𝟔𝟐𝟕𝑹𝒔 + 𝟎. 𝟔𝟕𝟖𝟎𝑮𝒔 + 𝟎. 𝟎𝟓𝟗𝟑𝑩𝒔
𝑬 𝑬′
𝑭𝑫
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
HLG
Decoding
OOTF
HLG EOTF
127

• Note 5d – In this Recommendation, when referring to the luminance of a single colour component (RD, GD,
BD), it means the luminance of an equivalent achromatic signal with all three colour components having
that same value.
• Note 5e – This EOTF applies gamma to the luminance component of the signal, whereas some legacy
displays may apply gamma separately to colour components. Such legacy displays approximate this
reference OOTF.
• Note 5f – For displays with nominal peak luminance (LW) greater than 1000 cd/m², or where the effective
nominal peak luminance is reduced through the use of a contrast control, the system gamma value
should be adjusted according to the formula below, and may be rounded to three significant digits:
γ = 1.2 + 0.42 log10(
LW
1000
)
128

• Note 5g – The system gamma value may be decreased for brighter background and surround conditions.
• Note 5i – The inverse of HLG OOTF is derived as follows:
• For processing purposes, when the actual display is not known, 𝜶 may be set to 1.0 cd/m².
𝑹𝑺 = (
𝒀𝑫
𝜶
)
𝟏−𝜸
𝜸 𝑹𝑫
𝜶
𝒀𝑫 = 𝟎. 𝟐𝟔𝟐𝟕𝑹𝑫 + 𝟎. 𝟔𝟕𝟖𝟎𝑮𝑫 + 𝟎. 𝟎𝟓𝟗𝟑𝑩𝑫
𝑮𝑺 = (
𝒀𝑫
𝜶
)
𝟏−𝜸
𝜸 𝑮𝑫
𝜶
𝑩𝑺 = (
𝒀𝑫
𝜶
)
𝟏−𝜸
𝜸 𝑩𝑫
𝜶
129

Parameter Values
Input signal to HLG EOTF
𝑬′: Non-linear HLG encoded signal.
The EOTF maps the non-linear HLG signal into display light.
HLG Reference EOTF
Note 5h:
• During production, signal values are expected to
exceed the range E′ = [0:1]. This provides processing
headroom and avoids signal degradation during
cascaded processing.
• Such values of E′, below 0 or exceeding 1, should not
be clipped during production and exchange.
• Values below 0 should not be clipped in reference
displays (even though they represent “negative”
light) to allow the black level of the signal (LB) to be
properly set using test signals known as “PLUGE”.
𝑭𝑫 is the luminance of a displayed linear component signal {RD, GD, BD}, in 𝒄𝒅/𝒎𝟐.
𝑬′ is the non-linear signal {𝑹′, 𝑮′, 𝑩′} as defined for the HLG Reference OETF. 5h
OOTF[ ] is as defined for the HLG Reference OOTF.
𝐎𝐄𝐓𝐅−𝟏[] is:
The values of parameters 𝒂, 𝒃, and 𝒄 are as defined for the HLG Reference OETF.
β is the variable for user black level lift and:
𝑳𝑾 is nominal peak luminance of the display in 𝒄𝒅/𝒎𝟐 for achromatic pixels.
𝑳𝑩 is the display luminance for black in 𝒄𝒅/𝒎𝟐.
𝑭𝑫 = 𝑬𝑶𝑻𝑭 𝐦𝐚𝐱 𝟎, 𝟏 − 𝜷 𝑬′
+ 𝜷
𝑭𝑫 = 𝑶𝑶𝑻𝑭[𝑶𝑬𝑻𝑭−𝟏
𝒎𝒂𝒙 𝟎, 𝟏 − 𝜷 𝑬′
+ 𝜷 ]
𝑬 𝑬′
𝑭𝑫
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
HLG
Decoding
OOTF
HLG EOTF
𝑬 = 𝑶𝑬𝑻𝑭−𝟏 𝑬′ =
𝑬′𝟐
𝟑
𝟎 ≤ 𝑬′
≤
𝟏
𝟏𝟐
𝒆(
𝑬′−𝒄
𝒂
)
+ 𝒃
𝟏𝟐
𝟏
𝟏𝟐
< 𝑬′
≤ 𝟏
𝜷 = 𝟑
𝑳𝑩
𝑳𝑾
ൗ
𝟏
𝜸
130

Increasing Colour Saturation with Leaving the Overall Tone Curve Unchanged in HLG
– The HLG OOTF (system gamma applied on luminance) uses scene-referred camera signals that result in a
display that closely preserves the chromaticity of the scene as imaged by the camera.
– This differs from the traditional colour reproduction provided by the HDTV and UHDTV OOTFs, which
produce more saturated colours which viewers of existing SDR content have become familiar with.
Traditional Colour Reproduction for Camera Signals
HLG HDR firmware
1000 nits peak
luminance
HDR Signal
Scene-referred Camera Signals
It preserves the
chromaticity of the scene
SDR Mode
(ITU-R BT.1886, 100
nits peak luminance)
SDR Signal More Saturated Colours
132

Increasing Colour Saturation with Leaving the Overall Tone Curve Unchanged in HLG
– The effect of applying following processing is to increase colour saturation whilst leaving the overall tone
curve unchanged.
Traditional Colour Reproduction for Camera Signals
Applying gamma separately to
red, green and blue components:
It does two things:
• Firstly, it adjusts the
overall tone curve.
• Secondly, because it is
applied separately to the
colour components, the
colour saturation is
increased.
Applying an inverse gamma (𝛾= 1/1.2) to the luminance component:
• It undoes the modification of the tone curve by applying an inverse gamma (𝛾=
1/1.2) to the luminance component of the signal.
• Applying gamma to the luminance component only (as in the HLG OOTF) leaves
the ratio of the red to green to blue components unchanged and, hence, does
not change the saturation.
• Conversely, it would be possible to use similar processing to modify a signal
representing the traditional look to instead more closely represent the
chromaticity of the scene as imaged by the camera.
Inverse Gamma
Scene
Light HLG OETF
Encoding
𝜸 = 𝟏. 𝟐 Applied on
R, G, B
𝜸 = 𝟏/𝟏. 𝟐 applied
on Luminance
HLG Scene-
referred Signal
Saturation
overall tone curve is change.
Saturation
overall tone curve is unchanged
133

– The HLG signal characteristic is similar to that of a SDR camera with a “knee” and no production metadata
is requires.
– HLG is not specified for use with metadata, and instead has a specified relationship between overall
system gamma (implemented as part of the display EOTF) and peak display brightness.
– An overall system gamma of 1.2 is specified for HLG when displayed on a 1,000 nit monitor.
a = 0.17883277
b = 0.28466892
c = 0.55991073
Linear Scene Light
Signal
Level
SDR OETF
SDR with Knee
HDR HLG OETF
Relationship Between Overall System Gamma and Peak Display Brightness
HLG HDR Display
1000 nits
HDR Signal
𝜸𝑺𝒚𝒔𝒕𝒆𝒎 = 𝟏. 𝟐
134

− In HDR TV, the brightness of displays and backgrounds/surround will vary widely, and the system gamma
will need to vary accordingly.
1- NHK indoor test scene for a 1000 nits reference display and 2000 nits display:
− Lighting was adjusted so that the luminance level of the diffuse white was 1200 𝑐𝑑/𝑚2
.
− The subjects were requested to adjust the system gamma and camera iris with reference to the real scene so that
a tone reproduction similar to the scene could be obtained on the display.
• For a 1000 nits OLED display (Sony BVM-X300) the average optimum system gamma was found to be 1.18
• For a 2000 nits peak luminance LCD display (Canon DP-V3010), the average preferred system gamma was 1.29
Appropriate System Gamma, Test 1
Sony BVM-X300 OLED display, 1000 nits
HLG HDR Display
1000 nits
HLG HDR Display
2000 nits
Canon DP-V3010 LCD display, 2000 nits
HDR Signal
System Gamma
Changing
Camera Iris
Changing
Target: A Similar Tone Reproduction to the Scene
by HDR Displays with Different Peak Luminances
135

2- BBC tests for delivering the best compatible SDR image:
− Similarly, the BBC conducted subjective tests to determine the value of system gamma that delivers the best
compatible SDR image (backwards compatibility with SDR displays).
• The value of system gamma that delivers the best SDR compatible picture with a 1000 nits display was 1.29
Sony BVM-X300 OLED display in SDR mode
SDR Mode
(ITU-R BT.1886, 100
nits peak luminance)
HLG HDR firmware
500 nits peak
luminance
Sony BVM-X300 OLED display in HDR mode
System Gamma
Changing
Camera Iris
Changing
HDR Signal
HLG HDR firmware
1000 nits peak
luminance
Sony BVM-X300 OLED display in HDR mode
SDR Signal
Target: To deliver Best Compatibility SDR Image
by HDR Displays with Different Peak Luminances
136

1- NHK indoor test scene for a 1000 nits reference display and 2000 nits display:
• For a 1000 nits OLED display (Sony BVM-X300) the average optimum system gamma was found to be 1.18
• For a 2000 nits peak luminance LCD display (Canon DP-V3010), the average preferred system gamma was 1.29
2- BBC tests for delivering the best compatible SDR image:
Result: Appropriate System Gamma
When designing the HLG HDR system, it was considered more important to weigh the
choice of gamma value in favour of HDR production, rather than backwards compatibility
with SDR displays. So a value of 1.20 was adopted for the reference 1000 cd/m² display.
137

Reference Peak
Brightness
Display
Non-Reference
Peak Brightness
Display Test subjects were asked to perceptually match as
closely as possible an image by adjusting the system
gamma applied to the non-reference brightness image.
(in a fixed background luminance of 5 nits)
Gamma
Changing
The pictures from HDR linear light
images from Mark Fairchild’s HDR
Photographic Survey (Image
peak luminance are different).
– From Previous Tests The system gamma needs to vary according to display peak brightness.
– New Tests The system gamma needs to vary according to image peak luminance's.
Two tests have been done:
Test 1: corresponds to peak luminances from 1000 to 4000 cd/m²
Test 2: from 100 to 1000 cd/m²
• Both tests are normalised so that gamma=1.2 at 1000 cd/m²
Target: to Match Images with Different
Peak Luminance with HDR Displays with
Different Peak Luminances
138

Test 1 corresponds to images with peak luminances from 1000 to 4000 nits.
Test 2 corresponds to images with peak luminances from 100 to 1000 nits.
Both tests are normalized so that gamma=1.2 at 1000 nits.
0.6
0.7
0.8
0.9
1
1.1
1.2
1.3
1.4
1.5
100 1000
Gamma
Peak image luminance in cd/m2
Test 1
Test 2
ITU
Rec BT.2100 Note 5e:  = 1.2 at the nominal display peak luminance of 1000 cd/m².
Gamma
Target: to Match Images with Different
Peak Luminance with HDR Displays with
Different Peak Luminances
𝛄 = 𝟏. 𝟐 ∗ 𝜿 )
𝐋𝐨𝐠𝟐(𝑳 Τ
𝒘 𝟏𝟎𝟎𝟎 κ = 1.111
𝜸 = 𝟏. 𝟐 + 𝟎. 𝟒𝟐 𝒍𝒐𝒈𝟏𝟎(
𝑳𝑾
𝟏𝟎𝟎𝟎
)
𝑳𝑾
400 cd/m² to 2000 cd/m²
139

− Bringing together the results of all studies, it is found that the appropriate system gamma (𝛄) for different
brightness displays, in the reference environment, can be determined using the following equation:
𝐋𝐖 : Nominal peak luminance of the display in nits
− According to the subjective tests conducted by the BBC, displays for a range of different values of
nominal peak luminance, specifically the range from 400 cd/m² to 2000 cd/m², can be shown to provide
a consistent look by varying the value of gamma in the HLG OOTF in accordance with the equation
above.
− This allows programmes to be made using displays with different peak luminance.
𝛾 = 1.2 + 0.42 𝑙𝑜𝑔10(
𝐿𝑊
1000
)
Appropriate System Gamma for Different Brightness Displays (Reference Environment)
140

− Outside this range of peak luminance (Outside 400 cd/m² to 2000 cd/m²) the match of this simple model
to the experimental detail starts to deteriorate.
− An extended model, “Extended Model” illustrated in the figure ., is given by:
− This may be used for displays with peak luminance outside the range above (outside 400 cd/m² to 2000
cd/m²).
− Within that range the two models are virtually identical and will provide equally good performance.
− It should be noted that using a gamma adjustment to adapt to different peak luminances has its
limitations.
• Television receivers typically apply different and more sophisticated methods.
• The acceptability of displays with different peak luminance values is a decision for individual
producers, and might differ between productions.
𝛄 = 𝟏. 𝟐 ∗ 𝜿 )
𝐋𝐨𝐠𝟐(𝑳 Τ
𝒘 𝟏𝟎𝟎𝟎 where: κ = 1.111
Appropriate System Gamma for Different Brightness Displays (Reference Environment)
141

− The luminance on a production monitor corresponding to nominal peak, 100%, signal level, should be
adjusted to a comfortable level for the viewing environment.
− The nominal peak luminance of 1000 𝒄𝒅/𝒎𝟐
, identified in Recommendation ITU-R BT.2100, has been found to
work well in typical production environments.
− The system gamma value may be decreased for brighter background and surround conditions.
Appropriate System Gamma for Non-Reference Environments
OB truck Studio
HLG HDR Display
1000 nits Peak
luminance
Nominal peak signal level (100% signal level) does not have to be set to the peak
luminance of the monitor, which may be too bright for comfortable viewing.
E.g. by decreasing system gamma we set nominal peak signal level to 950
nits to compensate for the differences in the adaptation state of the eye.
HLG Signal
5 cd/m²
142

− Many television programmes are produced in environments that differ considerably from the reference
viewing environment.
− The luminance of the surround may be considerably higher than the recommended 5 cd/m².
− Recommendation ITU-R BT.2100 recognises that the HLG display gamma may need to be reduced in
brighter viewing environments, to compensate for the differences in the adaptation state of the eye.
OB truck Studio
Many television programmes are produced in environments that differ considerably from the reference viewing environment.
143

− The BBC conducted subjective tests to measure the change in gamma necessary to perceptually match
images displayed across a range of peak luminances in the reference and in non-reference
environments.
− By adjusting the display gamma to compensate for non-reference viewing environments more consistent
results may be achieved in a wide range of production environments.
− Twenty-one viewers participated in the tests. The results, from 21 viewers, that show the reduction in
gamma as the surround brightness increases are presented below in the figure .
HLG HDR Display
1000 nits Peak
luminance
Nominal peak signal level (100% signal level) does not
have to be set to the peak luminance of the monitor.
By changing system gamma we set nominal peak signal level to appropriate
value to compensate for the differences in the adaptation state of the eye.
HLG Signal
948 nit 990 nits 980 nits …
100% signal level 100% signal level 100% signal level …
144

100 𝒄𝒅/𝒎𝟐 Peak Brightness
1000 𝒄𝒅/𝒎𝟐
Peak Brightness
2000 𝒄𝒅/𝒎𝟐
Peak Brightness
Reduction in gamma as the surround brightness increases to
compensate for the differences in the adaptation state of the eye.
γ = 1.2 + 0.42 log10(
LW
1000
)
Equation
145

− The line of best fit, which provides an indication of how gamma should be adjusted in non-reference
environments, is given by the equation below:
𝜸𝒃𝒓𝒊𝒈𝒉𝒕 : system gamma for display surrounds greater than 5 cd/m²
𝜸𝒓𝒆𝒇 : system gamma for reference environment
𝑳𝒂𝒎𝒃 : ambient luminance level in cd/m².
− An alternative model which matches the form of the “extended model” for the variation of gamma with
peak display luminance and which also includes the variation of gamma with surround luminance is as
flows where 𝛾𝑟𝑒𝑓 is 1.2, µ = 0.98 , κ = 1.111 and the reference surround luminance 𝐿𝑟𝑒𝑓𝑒𝑟𝑒𝑛𝑐𝑒 is 5 cd/m².:
𝜸𝒃𝒓𝒊𝒈𝒉𝒕 = 𝛄𝒓𝒆𝒇 − 𝟎. 𝟎𝟕𝟔 𝐥𝐨𝐠𝟏𝟎
𝑳𝒂𝒎𝒃
𝟓
   
ref
surround
surround
ref
W L
L
L
L 2
2 Log
Log
ref
γ
γ 
 


146

Code Values 64 –940
Code Values 64 -940
Code Values 64 -940
Code Values 64 - 940
e.g. code values 64 - 940
HLG Represents Relative Brightness
e.g. OB truck
e.g. studio gallery
• The signal is constant with different mastering displays.
• Display adaptation inherent part of HLG EOTF 147

HLG is based on Relative Brightness, Just Like Existing TV Systems
− Signal independent of the display
• Utilises entire code range regardless of mastering monitor
• Preserves the value of the archive as consumer displays get brighter
− Engineers and Craft staff read waveform monitors in the conventional way
− By design, entire image gets brighter as display brightness increases
• Allows HDR viewing in brighter environments whilst maintain the creative intent
• Allows consistent signals across a wide range of production environments and displays
148

HDR Viewing in Home Environments
− Essential that HDR TV is suitable for HOME viewing environments
− Absolute brightness approach of PQ is well suited to Cinema where all viewing environments are the
same.
− Relative brightness approach of HLG, well suited to diverse home TV viewing.
• The viewers should not have to draw curtains during the daytime to watch HDR-TV.
• To preserve details in the blacks, presentation needs to be brighter than in grading suite
• To preserve the impact of highlights, consumer screens may need to be brighter than grading screens
• HDMI 2.0b (HLG software upgrade)
Grading Suite, Grating Screen Presentation, Consumer Screens
149

Relative Light Approach of HLG Allows HDR Viewing All Day Long
− By design as HLG displays get brighter so does entire image, enabling HDR in brighter environments, e.g.,
Home Theatre Projector
e.g. 400 cd/m² peak
Graphics “Ref” (75% HLG), 100 cd/m²
Dim Evening Living Room
Bright Daytime Living Room
Environment Simulated images
150

Recall: Gamma Adjustment Allows Consistent Signals to be Produced
− Following specifies how the display’s gamma is adjusted to compensate for changes in the response of the
human visual system as the eye adapts, when using HLG displays of different peak luminance.
• The gamma adjustment allows consistent signals to be produced from a range of displays with different
peak luminance.
− The display’s gamma should further be adjusted to compensate for the adaptation state of the eye in non-
reference production environments.
• The gamma adjustment allows consistent signals to be produced in non-reference production
environments.
γ = 1.2 + 0.42 log10(
LW
1000
)
γ𝑏𝑟𝑖𝑔ℎ𝑡 = γ𝑟𝑒𝑓 − 0.076 log10
𝐿𝑎𝑚𝑏
5
151

Display of HLG Signals
The contrast, brightness and display system gamma (𝜶, 𝜷 and 𝜸 in OOTF and EOTF) are adjusted according
to the viewing environment and nominal peak luminance of the display, as appropriate.
𝜸−𝟏
𝑹𝑺
𝜸−𝟏
𝑮𝑺
𝜸−𝟏
𝑩𝑺
𝒀𝒔 = 𝟎. 𝟐𝟔𝟐𝟕𝑹𝒔 + 𝟎. 𝟔𝟕𝟖𝟎𝑮𝒔 + 𝟎. 𝟎𝟓𝟗𝟑𝑩𝒔
𝑭𝑫 = 𝑬𝑶𝑻𝑭 𝐦𝐚𝐱 𝟎, 𝟏 − 𝜷 𝑬′
+ 𝜷
𝑭𝑫 = 𝑶𝑶𝑻𝑭[𝑶𝑬𝑻𝑭−𝟏
𝒎𝒂𝒙 𝟎, 𝟏 − 𝜷 𝑬′
+ 𝜷 ]
𝑬 = 𝑶𝑬𝑻𝑭−𝟏
𝑬′
=
𝑬′𝟐
𝟑
𝟎 ≤ 𝑬′
≤
𝟏
𝟏𝟐
𝒆(
𝑬′−𝒄
𝒂
)
+ 𝒃
𝟏𝟐
𝟏
𝟏𝟐
< 𝑬′
≤ 𝟏
𝜷 = 𝟑
𝑳𝑩
𝑳𝑾
ൗ
𝟏
𝜸
𝜸−𝟏
𝑬
152

Display of HLG Signals (1)
− Firstly, the monitor gamma is adjusted to the appropriate value for the target nominal peak luminance of the
display. The target nominal peak luminance may depend on the viewing environment.
• Table shows the gamma values for a range of typical production monitors in the reference viewing
environment (5 𝒄𝒅/𝒎𝟐
surround).
• For displays with nominal peak luminance (𝐿𝑊) greater than 1000 𝒄𝒅/𝒎𝟐
, or where the effective nominal
peak luminance is reduced through the use of a contrast control, the system gamma value should be
adjusted according to the formula, and may be rounded to three significant digits:
𝛾 = 1.2 + 0.42 𝑙𝑜𝑔10(
𝐿𝑊
1000
)
HLG Display Gamma
Nominal Peak Luminance (cd/m²) Display Gamma
400 1.03
600 1.11
800 1.16
1000 1.20
1500 1.27
2000 1.33 153

− Secondly, the display’s nominal peak luminance signal is adjusted using the user gain control (legacy
“contrast” control) and a photometer (luminance meter), with an HDR reference white (75% HLG) window test
patch (typically 1% screen area).
• Table shows the luminance levels for a range of typical production monitors.
Test Patch Luminance Levels for Different Nominal Peak Displays (HLG)
(the luminance levels for a range of typical production monitors)
Nominal Peak Luminance (cd/m²) HDR Reference White (cd/m²)
400 101
600 138
800 172
1000 203
1500 276
2000 343
154

− Thirdly, in non-reference viewing environments, a further adjustment should be made to the display’s system
gamma to compensate for the adaptation state of the eye.
• The Table illustrates the recommended gamma adjustments for a range of common production
environments, assuming a surround reflectance of approximately 60%, typical of light coloured walls.
• However, for the greatest signal consistency, the reference conditions specified in ITU-R BT.2100 should be
used.
Typical Environment Typical Illumination ∗ (Lux) Typical Luminance (cd/m²) Typical Gamma Adjustment
Office Based Production, Sunny Day 130 25 −0.05
Office Based Production, Cloudy Day 75 15 −0.04
Edit Suite 50 10 −0.02
Grading Suite 25 5 0.00
Production Gallery/Dark Grading Suite 3 0.5 +0.08
Typical production environments with different surround conditions
* Measured perpendicular to the screen.
155

− As a guide, a gamma adjustment of 0.03 is just visible to the expert viewer when viewed side-by-side.
• Thus, no additional gamma adjustment is necessary across the majority of critical television production
environments.
− However, a gamma adjustment is suggested for bright environments such as those sometimes used for news
production, or where a colourist prefers to work in a very dark environment.
− Lastly, the display black level is adjusted using the black level lift control (legacy “brightness” control) and
the Recommendation ITU-R BT.814 PLUGE signal, such that the negative stripes on the test pattern disappear,
whilst the positive stripes remain visible.
156

What range of luminances are judged comfortable by viewers?
− A number of SDR images (static images) that, on a 100 cd/m² reference monitor, varied in average
luminance over a range of 10-50 cd/m², were used.
− The study was conducted using a relative display system that employed a 3500 cd/m² display that was
adjusted to simulate a range of display luminance levels, thus the results are relevant to the HLG system that
also employs displays with relative luminance.
− Peak luminances of 500, 1000, 2000, and 2500 cd/m² were simulated.
− Viewers were asked to judge whether images were
• “Appropriate”
• “Too Bright
• “Too Dark”
Comfortable Brightness of Static Images
SDR Images with
average luminance
variation: 10-50 cd/m².
(on a 100 cd/m²
reference monitor)
HDR Display, up to
3500 cd/m²
To simulate a range of display luminance
levels (500, 1000, 2000, and 2500 cd/m² )
In reference viewing environment (dim surround)
(NHK)
By simulate
157

Peak luminance 500 cd/m² Peak luminance 1000 cd/m²
158

Peak luminance 2000 cd/m² Peak luminance 2500 cd/m²
159

− For each simulated display peak luminance,
• Images with average luminance less than 25% of the peak luminance being simulated were not judged
as “too bright” by many viewers.
• Images with average luminance greater than 25% of peak luminance began to be judged as “too
bright” by many viewers.
− The judgements were essentially independent of the peak luminance being simulated on the display; this
indicates that viewers’ eyes were adapting to the different display luminances.
The implication of these results is that HLG images with average luminance
of less than 250 cd/m² on a 1000 cd/m² HLG monitor, would not be judged
as too bright on an HLG monitor of any luminance up to at least 2500 cd/m².
160

Comfortable Brightness of Dynamic Images (Video Sequences)
− Having seen HDR video sequences on HLG displays with peak luminance levels of 1000 cd/m² and 4000
cd/m².
− These scenes had average luminance levels of 268 and 363 cd/m² on a 1000 cd/m² display.
• 25% of subjects commented informally that the brightest scenes were uncomfortably bright regardless of
any jumps.
HLG HDR Display
1000 nits Peak
luminance
HLG
Signal
HLG HDR Display
4000 nits Peak
luminance
HLG
Signal
Average
luminance levels of
268 and 363 cd/m²
161

Comfortable Brightness of Dynamic Images (Video Sequences)
− Having seen HDR video sequences on HLG displays with peak luminance levels of 1000 cd/m² and 4000
cd/m².
− These scenes had average luminance levels of 144 and 128 cd/m² on a 1000 cd/m² display.
• Similar comments were not made about the test scenes that had average luminances of 144 and 128
cd/m² on a 1000 cd/m² display.
HLG HDR Display
1000 nits Peak
luminance
HLG
Signal
HLG HDR Display
4000 nits Peak
luminance
HLG
Signal
Average
luminance levels of
144 and 128 cd/m²
Even when the static levels would be acceptable, sudden changes in
brightness can be uncomfortable, so different requirements are needed to
ensure viewer comfort when brightness jumps can occur.
162

Tolerance to Programme Brightness Shifts
− Unexpected changes in image brightness might occur between programmes, for example with interstitials.
− It is important to ensure that the brightness variations within HDR programmes are constrained to avoid viewer
discomfort.
− What is viewer tolerance to sudden changes in overall brightness for HDR television, using the mean pixel
display luminance as a measure of brightness?
− BBC test situation and results:
• The luminance behind the screen is 5 cd/m²
• The peak screen luminance is 1000 cd/m².
• Subjects were asked to rate the change in overall brightness between two still HDR images.
⇒ The measure has been shown to correlate well with subjective ratings of the overall brightness
⇒ But there may occasionally be a scene with an inhomogeneous luminance distribution where the
measure does not fully correspond to subjective brightness.
HLG HDR Display
1000 nits Peak
luminance
HLG Still Image 1
HLG Still Image 2
163

Transitions from mean luminance A (cd/m²)
to mean luminance B (cd/m²)
categorised by level of annoyance
− Two regions are marked in the figure with thick blue lines.
• The inner region, with mean display luminance levels
of 5 to 80 cd/m², contains only one possible “slightly
annoying” jump, and so could be considered a
suitable range for operation that will not cause viewer
discomfort.
• The outer region, with mean display luminance levels
up to 160 cd/m², includes several “slightly annoying”
jumps, and so could be considered an extended
range for creative effect.
− Further experiments reported by the BBC show that this
outer region can be extended down to 2.5 cd/m², and
production trials with a prototype meter suggest that this
extended range is appropriate.
164

− Specific delivery requirements for luminance ranges are left to individual service providers, depending on
their requirements.
− An example of requirement could be that the suggested ranges can be freely exceeded over a short
timescale, but the mean luminance over the length of a programme is kept within an operating range of 5 to
80 cd/m².
• It should be noted that this range still allows for significant differences in brightness between programmes,
so, for example, a “moody” or “bright” look can be achieved overall.
Short Timescale Short Timescale
Dynamic
Range
Time
165

− The eye adapts to a particular luminance level.
• Hence the scene-light levels corresponding to specified brightness shift tolerances are likely to be
broadly applicable for HLG displays over a range of different peak luminances.
− This is supported by experiments reported by the BBC, which suggest that the ranges (5 to 80 cd/m²) are
applicable for HLG displays up to a peak luminance of 4000 cd/m².
− It should be noted that shadow detail may be lost after a transition from a bright scene to a very dark scene,
even if the transition is not uncomfortable, because it takes time for the eyes to adapt.
− Also, a comfortable overall brightness does not ensure that the content makes good use of the available
dynamic range.
166

HLG and PQ Backwards Compatibility with SDR Displays
SDR Monitor (HD PQ)
HDR Monitor (4K HLG) SDR Monitor (HD HLG)
Slim
Wide & Tall
HDR Monitor (4K PQ)
167

HDR Signal
SDR UHDTV
ITU-R BT.709 Color Space
HDR metadata simply is ignored
(Limited Compatibility)
(Color Signal) (B & W Display)
– Most of encoder/decoder and TVs are SDR (encoders/decoders replacement !!?? )
– Settling on an approach that doesn’t require the replacement of encoders/decoders is very important to
some pay TV companies, distributors and device manufacturers.
– Both HLG and PQ include in DVB, ARIB and YouTube for HDR TV Distribution
– Backwards compatibility is less of an issue in some distribution ecosystems, such as over-the-top (OTT).
– A situation could arise in which supporting HDR would require the change of encoders, decoders and
cable set-top boxes.
Slim
Wide & Tall
168

HLG
BT.2020
SDR
BT.2020 Color Space
• It has a degree of compatibility.
• Hue changes can be perceptible in bright areas
of highly saturated color or very high code
values (specular highlights in small proportion of
the picture)
• Both PQ and HLG provide limited
compatibility when directly connected to
legacy SDR displays with BT.709
colorimetry.
HLG/PQ
BT.2020
SDR
BT.709 Color Space
– Non backwards-compatible approaches no doubt will lead to significant expense to various members of
the ecosystem because maintaining two sets of content (SDR and HDR) may become necessary.
 Both HLG and PQ are backward compatible.
 Dolby Vision, Technicolor, Philips, Samsung and BBC/NHK are all backwards compatible.
Slim
Wide
Wide & Tall
169

HLG and PQ signals Conversion to SDR BT.709
– When PQ or HLG HDR signals are converted for use in SDR ITU-R BT.709 facilities, the conversion process is
expected to perform following conversion in such a way as to minimize perceptible changes in color for
all types of HDR content, regardless of the code value ranges in use.
• The color space
• HDR to SDR
• Any video format conversion (UHD to HD,…)
PQ or HLG HDR signals SDR BT.709 Signal
Slim
Wide & Tall
170

Display of HLG Signals on SDR Screens
− For best results when displaying HLG signals on SDR screens, the SDR monitor should support the
Recommendation ITU-R BT.2020 (BT.2020) colour gamut.
− However, BT.709 colour monitors will show a de-saturated image with visible hue shifts.
− A three-dimensional look-up table (3D-LUT) may be included in the monitoring chain to down-convert from
BT.2100 HDR signals to BT.709 SDR, minimising colour distortions on such displays.
− Suitable look-up tables are often included within the display monitors themselves.
HLG
BT.2020
SDR
BT.709 Display
• De-saturated image
• Visible hue shifts
Slim
Wide & Tall
Wide
171

– The design of the HLG HDR signal parameters is intended to allow distribution networks to provide a single
bit stream that can target both SDR and HDR receivers, where those SDR receivers support the
Recommendation ITU-R BT.2020 color container.
Single Video Stream
(HLG HDR, BT. 2020)
It may produce acceptable
results on SDR displays
HDR (4K HLG)
SDR Display
HLG HDR Display
HLG Backwards Compatibility with SDR Display
Slim
Wide & Tall
Wide & Tall
172

– The acceptability of the degree of compatibility of HLG might be a commercial decision by specific
broadcasters or for a specific application.
– HLG is compatible with conventional standard dynamic range production equipment, tools and
infrastructure:
• Thus HDR monitors are only necessary in critical monitoring areas.
• Non-critical production monitors, such as multi-view production monitors, may be SDR BT.709 displays.
• For simple confirmation of the presence or absence of a signal, SDR BT.709 display may be sufficient.
4K HDR Monitor (HLG) HD SDR Monitor (HLG)
Wide & Tall
Slim
173

– When a hybrid log gamma HDR video
signal is displayed on a conventional SDR
display the effect is similar to the use of a
digital camera with a knee.
– It is not surprising therefore, that the HLG
video signal is highly compatible with
conventional SDR displays, because what
you see is very similar to the signal from an
SDR camera.
– The knee characteristic of the HLG
characteristic, defined in ITU-R BT.2100
provides an extended range that is
conservative compared with current SDR
practice.
a = 0.17883277
b = 0.28466892
c = 0.55991073
Linear Scene Light
Signal
Level
SDR OETF
SDR with Knee
HDR HLG OETF
Thanks to the use of a gamma curve for a large
part of the signal range, HLG signals provide
backward compatibility with legacy displays.
174

Live Output HLG Signal Adjustment
− SDR studio cameras are equipped with various image manipulation
functions such as black gamma, knee adjustment, color matrix
adjustment, and so on to manage difficult scene content and provide
more tools to deliver a desired look.
− In HDR shooting, the same image manipulation functions are
expected.
− The HDR compatible studio cameras have introduced black gamma,
knee adjustment, color matrix and similar image quality adjustment
functions popular in SDR to the HDR image, and therefore can create
an appropriate picture according to the scene content and the
sensibilities of the producer.
− With these adjustment capabilities confirmation of this picture quality is
critical, so we think that it is important to output directly viewable HDR
from the camera with HLG so it can be viewed as it adjusted.
175

− HLG developed to allow straightforward migration to HDR Television (Television Broadcasting)
• Supports a wide range of displays and environments ⇒ Delivers high quality pictures on diverse displays
• No need for metadata as OOTF is part of display EOTF⇒ Can be displayed unprocessed on SDR screen
− In TV Production HLG can use existing SDR infrastructure and monitoring displays
• Only critical monitoring requires HDR displays
− Metadata Free Operation Key to Unlocking Benefits
• Allows use of conventional circuits, routers, switchers and codecs
• Enables simple reliable and consistent production
• Delivers consistent results on consumer screens and devices
• Places no constraints on operational practices
 Even simple metadata prevents, mixes, DVE and complicates graphics
 Same issues apply in consumer equipment
HLG Enables Easy Migration to HDR TV Production & Distribution
176

HLG Enables Easy Migration to HDR TV Production & Distribution
− In Production:
• Requires no metadata
• Compatible with existing 10-bit infrastructure, codecs and equipment
• Provides compatible picture on SDR screens
• Migration only requires
 HDR cameras
 HDR displays in critical monitoring areas
− In Distribution:
• Supported by HEVC and HDMI 2.0b (via software upgrade)
• Specified (alongside PQ) by DVB, ARIB and YouTube
177

HDR in Distribution
− Both HLG and PQ Will be Supported in Devices in Most World Markets
− HLG and PQ Included in
• ARIB STD-B32, Video Coding, Audio Coding And Multiplexing Specifications for Digital Broadcasting
• DVB/ETSI TS 101 154 v2.3.1, Specification for the use of Video and Audio Coding in Broadcasting
Applications based on the MPEG-2 Transport Stream
• YouTube HDR
https://support.google.com/youtube/answer/7126552
• Korea announced will support both HLG and PQ
European Telecommunications Standards Institute (ETSI) 178

Subjective Evaluation of HLG for HDR and SDR distribution
179

Review of Rec 709, SMPTE 2084 and HLG
ITU-R BT.709 SDR (up to 100 nits)
– The reference EOTF (exponent function) used in HDTV.
HLG (Up to 1000 nits)
– It uses a logarithmic curve for the upper half of the
signal values which allows for a larger dynamic range
– It offers a degree of compatibility with legacy displays
by more closely matching the previously established
television transfer curves.
Perceptual Quantizer (PQ), SMPTE ST 2084 (up to 10,000 nits)
– In the darker areas of a picture, minor changes can be
seen much more than in brighter areas of a picture.
• More code words should be given to the darker
areas.
• For much brighter specular highlights, do not need
as many code words to represent them.
SDR HLG
PQ
181

PQ (Perceptual Quantization) HLG (Hybrid Log-Gamma)
Main curve Display EOTF (Absolute Value EOTF) Camera OETF (Relative Value OETF)
Target Production (Movie, OTT, Internet video streaming, packaging)
Prepared shooting environment or grading in sufficient time after shooting
Broadcast TV, live video
Downward compatible (to SDR)
Advantages Handles brightness in absolute values of up to 10,000 cd/m²
New gamma curve based on human visual perception
Handles brightness as relative values (same as existing
standards) up to 1000 cd/m²
Peak Brightness Absolute value of 10,000 cd/m²
The signal varies with mastering display.
Relative value of 1,000 cd/m²
The signal is constant with mastering display.
Black Level 0.005 cd/m² or lower 0.005 cd/m² or lower
Proposed by Dolby BBC & NHK
Reference Standards SMPTE ST 2084、ITU-R BT.2100 ARIB STB-B67 and ITU-R BT.2100
Reference
Standards
SMPTE ST 2084 & ITU-R BT.2100 Outstanding Good
Appearance on SDR TVs Poor Fair
Live Broadcasts Fair Outstanding
0 2000 4000 6000
1
0.2
0
0.4
0.6
0.8
Input
EOTF
8000 10000 0 500 1000 1500 2000
1
0.2
0
0.4
0.6
0.8
output
OETF
PQ and HLG Summary
182

Scene
Light
SDR
Signal
Camera
HLG
Signal
PQ
Signal
Sensor
Relative Linear Scene Light
(Volts)
Lens
Set Exposure (Iris)
Relative
Non-linear Signal
[0,1]
Absolute
Non-linear Signal
[0,1]
A Closer Look at the Camera
SDR OETF
(“Gamma”)
HLG OETF
PQ OETF
Relative
Non-linear Signal
[0,1]
184

Optical
Electronic
1023
768
512
256
400 600 800 1000 1200
OETF
E
Ref. white
(10bit)
O
200
100
0
0
ITU-R BT-709
S-log3
SMPTE ST2084
Hybrid Log-Gamma
940
Recorded
Code
Value
Relative Scene Luminance (Exposure)
SDR display
185

The CRT EOTF is commonly
known as gamma
Optical
Electronic
1023
768
512
256
400 600 800 1000 1200
EOTF
E
Ref. white
(10bit)
O
200
100
0
0
ITU-R BT-709
S-log3
SMPTE ST2084
Hybrid Log-Gamma
940
SDR display HDR display
Luminance on Display (𝒄𝒅/𝒎𝟐)
Recorded
Code
Value
186

Optical
Electronic
The CRT EOTF is commonly
known as gamma
Optical
Electronic
1023
768
512
256
400 600 800 1000 1200
OETF
E
Ref.white
(10bit)
O
200
100
0
0
ITU-R BT-709
S-log3
SMPTE ST2084
Hybrid Log-Gamma
940
Recorded
Code
Value
Relative Scene Luminance (Exposure)
SDR display
1023
768
512
256
400 600 800 1000 1200
EOTF
E
Ref.white
(10bit)
O
200
100
0
0
ITU-R BT-709
S-log3
SMPTE ST2084
Hybrid Log-Gamma
940
SDR display HDR display
Luminance on Display (𝒄𝒅/𝒎𝟐)
Recorded
Code
Value
187

1023
768
512
256
0
0 200 1000 1200
ITU-R BT-709
S-log3
SMPTE ST2084
Hybrid Log-Gamma
Recorded
data
value
400 600 800
HDR brightness
SDR brightness
Relative scene Luminance (exposure) 188

189

Same Look
System (total) gamma to adjust the final look of displayed images
(Actual Scene Light to Display Luminance Transfer Function)
OETF EOTF
190

Reference OOTF = OETF + EOTF
OETF
HLG/PQ
EOTF
HLG/PQ
𝑬: [𝟎, 𝟏] 𝑬′
: [𝟎, 𝟏]
𝑭𝑫
Linear Scene-light
Non-linear
191

Scene-Referred HDR System (HLG)
– The HLG signal describes the relative light in the scene
– The signal is specified by the camera OETF characteristic
– The signal produced by the camera is independent of the display
Display-Referred HDR System (PQ)
– The PQ signal describes the absolute output light from the mastering display
– The signal is specified by the mastering display EOTF characteristic (in production)
– The signal produced by the camera is dependent to the mastering display
Scene-Referred vs. Display-Referred
Mastering Display
1000 nits, 2000nits,…?
PQ
PQ Encoding
Display
Light
Display-referred
Video Signal PQ EOTF
HLG Encoding
Scene
Light
Scene-referred
Video Signal
HLG OETF
192

Scene-Referred HDR System (Scene-based) (HLG)
– The HLG signal is specified by the camera OETF and describes the relative scene light.
– Every pixel in the image represents the light intensity in the captured scene
– The signal produced by the camera is independent of the display.
– The Display EOTF output is normalized against the original scene brightness levels and not to any specific display.
– No metadata, making it suitable for live video production.
– Never needing further mastering and color correction for future displays.
– The HLG based HDR standard is ‘relative' so it is possible to increase the display's light output to overcome
surrounding room light levels. The TV can be made brighter to overcome uncontrollable light environments,
including the use of different gamma values (+)
The EOTF output values can therefore be considered as a percentage relative to the scene light
by the display, thus simplifying processing by the display to display light.
HLG Encoding
Scene
Light
Scene-referred
Video Signal
HLG OETF
193

Display-Referred HDR System (Display-based) (PQ)
– The PQ signal is specified by the mastering display EOTF and describes the absolute output light from it.
– The EOTF produces the absolute brightness levels as set on a reference display during production process.
– The brightness and color levels can be changed on a frame-by-frame (or scene-by-scene) basis by the colorist as
part of the artistic process to maintain the highest picture quality and rendering/artistic intent during the post
production process.
• Metadata is required in order to inform the consumer display of these changes as they occur.
– It may also require re-mastering in the future to support new display types.
– The PQ based HDR standard is 'absolute' so it is not possible to increase the display's light output to overcome
surrounding room light levels - the peak luminance cannot be increased, and neither can the fixed EOTF curve.(-)
The PQ curve’s maximum brightness is always mapped to the maximum brightness of the reference
display, so output values are effectively a percentage of the reference display scene brightness
Mastering Display
1000 nits, 2000nits,…?
PQ
PQ Encoding
Display
Light
Display-referred
Video Signal PQ EOTF
194

EOTF and OETF Standardization in Scene-Referred and Display-Referred Systems
Display-Referred (PQ):
– The PQ signal describes the
absolute output light from the
mastering display.
– The PQ signal is specified by the
mastering display EOTF
characteristic (in production).
Scene-Referred (HLG):
– The HLG signal produced by the
camera is independent of the
display.
– The HLG signal is specified by the
camera OETF.
Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
195

Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
PQ
EOTF
HLG
OETF
Display-Referred (PQ):
– The PQ signal describes the
absolute output light from the
mastering display.
– The PQ signal is specified by the
mastering display EOTF
characteristic (in production).
Scene-Referred (HLG):
– The HLG signal produced by the
camera is independent of the
display.
– The HLG signal is specified by the
camera OETF.
EOTF and OETF Standardization in Scene-Referred and Display-Referred Systems
196

– The “reference OOTF” compensates for difference in tonal perception between the environment of the
camera and that of the display specification.
Same Look
OOTF
Where is OOTF Position?
Scene-referred
Image Data
(HLG Codded)
HLG OETF HLG EOTF
Scene
Light
Display
Light
Display-referred
Image Data
(PQ Codded)
PQ OETF PQ EOTF
Scene
Light
Display
Light
OOTF
OOTF
197

Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
EOTF
OETF
198

Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
EOTF
OETF
OOTF 𝑬𝑶𝑻𝑭−𝟏
OOTF
𝑶𝑬𝑻𝑭−𝟏
Cancel
Cancel
199

Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
EOTF
OETF
OOTF
Cancel
Cancel
For viewing in the end-user consumer TV, a display mapping should be performed to adjust the reference OOTF in
viewer side on the basis of mastering peak luminance metadata of professional mastering display
OOTF is implemented within the display and is aware of its peak luminance and environment (no metadata is needed)
200

The HDR Broadcast Standard (BT.2100) OOTF on HDR
– The HDR broadcast standard (BT.2100) presents two options for OOTF on HDR as follows and opens the way
towards wider adoption of HDR broadcasting.
• Perceptual Quantization (PQ)
• Hybrid Log-Gamma (HLG)
– The PQ system was designed so that the OOTF is considered to be in the camera (or imposed in the
production process).
– The HLG system was designed so that the OOTF is considered to be in the display.
OOTF on HDR, defined by ITU-R BT.2100, includes PQ (Perceptual
Quantization) and HLG (Hybrid Log-Gamma)
201

Cancel
(seasoning)
EOTF-1
OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
OETF
Optical Signal
Scene Light
Electronic Signal
EOTF
OOTF Position in PQ
Output [%]
Input [cd/㎡ ]
Linear Scene Light
202

Cancel
(seasoning)
EOTF-1
OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
OETF
Optical Signal
Scene Light
Electronic Signal
EOTF
OOTF Position in PQ
Output [%]
Input [cd/㎡ ]
The PQ system specifies a display-referred HDR signal which means that the PQ signal describes the
absolute output light from the mastering display.
• Therefore, the mastering display EOTF transfer characteristics is implemented in the display and the
signal produced by the camera is dependent to the mastering display.
• That means that there is additional processing and metadata are required to convert the signal for a
particular screen.
Linear Scene Light
203

Cancel
(seasoning)
OETF-1 OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
EOTF
Optical Signal
Scene Light
Electronic Signal
OETF
Linear Scene Light
Output [%]
Input [cd/㎡ ]
204

Cancel
(seasoning)
OETF-1 OOTF
Input [%]
Output
[cd/㎡ ]
Camera Monitor
Display Light
EOTF
Optical Signal
Scene Light
Electronic Signal
OETF
Linear Scene Light
Output [%]
Input [cd/㎡ ]
The HLG system specifies a scene-referred HDR signal which means that every pixel value in the image
represents the light intensity in the captured scene.
• Therefore, the transfer characteristics can be implemented directly in the camera and the signal
produced by the camera is independent of the display.
• That means that there is no additional processing and no metadata are required to convert the signal
for a particular screen.
205

𝑬 𝑬′
Scene
Light
OOTF
Display-referred
Image Data
PQ OETF
PQ
EOTF
Display
Light
Decoding
Camera
Encoding
Mastering Display
Display
Light
Display Adjustment
OOTF
Adjust
PQ
EOTF
Decoding
Optional
Metadata
PQ
Metadata is needed for
display adjustment
The luminance of a displayed linear
𝑭𝑫
206

𝑬
linear component
Scene
Light
Scene-referred
Image Data
HLG OETF
Display
Light
Encoding
Reference Display
HLG
Decoding
OOTF
HLG EOTF
𝑬′
𝑭𝑫
linear component
Non-reference
Display Light
Non Reference Display and Environment
HLG
Decoding
OOTF
HLG EOTF
Reference
No Metadata is needed for
display adjustment
𝑬′
Display Adjustment
OOTF
Adjust
𝑭𝑫
Reference
207

Relationship between the OETF, EOTF and OOTF
System Transfer Function for CRT
OOTFSDR = OETF709, Camera × EOTF709, Display
System Transfer Function for LCD
OOTFSDR = OETF709, Camera × EOTF1886, Display
System Transfer Function for HDR
OOTFPQ = OETFPQ, Camera × EOTFPQ, Display
System Transfer Function for HDR
OOTFHLG = OETFHLG, Camera × EOTFHLG, Display
OETFHLG, Camera × OETF −𝟏
HLG, Display × OOTFHDR, Display
OOTFPQ, Camera × EOTF −𝟏
PQ, Camera × EOTFPQ, Display
Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
EOTF
OETF
OOTF
Cancel
Cancel
208

Relationship between the OETF, the EOTF and the OOTF
Concatenation
   
 
   
 
   
 
B
G
R
B
G
R
B
G
R
B
G
R
B
G
R
B
G
R
B
B
B
G
G
G
R
R
R
,
,
OETF
EOTF
,
,
OOTF
,
,
OETF
EOTF
,
,
OOTF
,
,
OETF
EOTF
,
,
OOTF



1
1
1
1
1
1
1
1
1
OOTF
EOTF
OETF
OETF
OOTF
EOTF
OETF
EOTF
OOTF
EOTF
OOTF
OETF
OOTF
OETF
EOTF
EOTF
OETF
OOTF





















Display
Light
Display
Light
Scene
Light
Scene
Light
OETF
OETF
EOTF
EOTF
Camera
Camera Display
Display
PQ
HLG
Standardized
Standardized
EOTF
OETF
OOTF
Cancel
Cancel
209

e.g. OB truck
e.g. studio gallery
Display
Re-mapping
e.g. Code Values 74 –636
• The signal varies with mastering display.
• Display re-mapping often required.
PQ Represents Absolute Brightness
Display
Re-mapping
Display
Re-mapping
Display
Re-mapping
210

Code Values 64 –940
Code Values 64 -940
Code Values 64 -940
Code Values 64 - 940
e.g. code values 64 - 940
HLG Represents Relative Brightness
e.g. OB truck
e.g. studio gallery
• The signal is constant with mastering displays.
• Display adaptation inherent part of HLG EOTF 211

HLG
− The signal is constant with mastering display
− Brighter display for brighter environment
− Image brightness changes with display brightness
− Dynamic Range of highlights is constant
• It is determined by diffuse white
− Display adaptation is an inherent part of HLG EOTF
PQ
− The signal varies with mastering display
− Brighter displays for more highlights
− Images brightness is constant with display brightness
− Dynamic range of highlights increases with peak
brightness of the display used for measuring
− Display re-mapping often required
Image Presentation
212

Artistic OOTF
– Using a “reference OOTF” allows consistent end-to-end image reproduction (to adjust the final look of
displayed image).
OOTF
Reference
Reference OOTF
Environment of
the Camera
Environment of
the Display
Scene Light
Reference
Display Light
213

Artistic OOTF
displayed image).
– Artistic adjustment may be made to enhance the picture. These alter the OOTF, which may then be called
the “Artistic OOTF”. Artistic adjustment may be applied either before or after the reference OOTF.
Environment of
the Camera
Environment of
the Display
Scene Light
Reference
Display Light
OOTF
Reference
Artistic OOTF
Artistic
Adjustment
Scene Light
Reference
Display Light
OOTF
Reference
Artistic
Adjustment
Environment of
the Camera
Environment of
the Display
OR
214

Artistic OOTF
displayed image).
– Artistic adjustment may be made to enhance the picture. These alter the OOTF, which may then be called
the “Artistic OOTF”. Artistic adjustment may be applied either before or after the reference OOTF.
– In general the Artistic OOTF is a concatenation of the OETF, artistic adjustments, and the EOTF.
Environment of
the Camera
Environment of
the Display
Scene Light
Reference
Display Light
Artistic
Adjustment
OETF EOTF
Artistic OOTF
215

⇒ Use of a “reference OOTF” allows consistent end-to-end image reproduction
⇒ To adjust the final look (colours and tones) of displayed image.
− OOTF is recognized as a overall system gamma, “overall system non-linearity” or “total gamma”
• Overall System gamma to adjust the final look of displayed images
• Actual scene linear light to display linear luminance transfer function
OETF, EOTF and OOTF Summary
216

Look
• The native appearance of colours and tones of a particular system (for example, PQ, HLG, BT.709) as seen
by the viewer.
• A characteristic of the displayed image.
Artistic/Creative Intent (⇒ Artistic Rendering Intent)
• A creative choice that the programme maker would like to preserve, primarily conveyed through the use
of colour and tone.
Rendering Intent (OOTF Gamma) (⇒ Adjustment Rendering Intent)
1. Rendering Intent is critical as display capabilities are so diverse (different display brightness).
2. Rendering intent is needed to compensate for the psychovisual effects of watching an emissive screen in a
dark or dim environment, which affects the adaptation state (and hence the sensitivity) of the eye.
• The “rendering intent” is defined by the OOTF.
• OOTF varies according to display brightness and viewing environment.
OETF, EOTF and OOTF Summary
217

Artistic (“Creative”) Intent
– Brighter environments need brighter pictures
– Different environments need different display gamma.
– Preserving luminance does NOT maintain creative intent
– The HLG signal, representing the camera output, remains constant.
• HLG displays adapt to preserve artistic intent (defined in BT2100).
– The PQ signal represents the image specifically for a reference display.
• Dim environment only
 Adaption for other brightness and environments ill-defined
218

Artistic (“Creative”) Intent
In Dim Environment
– Consumer Display Brightness = Production Display Brightness
• Both PQ and HLG maintain creative intent.
– Consumer Display Brightness < Production Display Brightness
• HLG: Dimmer image – but maintains creative intent.
• PQ: Highlights crushed (desaturated), reduced creative intent.
– Consumer Display Brightness > Production Display Brightness
• HLG: Brighter image – and maintains creative intent.
• PQ: Maintains creative intent . But versioning (archive) issue.
In Brighter Environment (& Consumer Brighter Display)
• HLG brighter image , no banding , maintains creative intent.
• PQ brighter image , increased banding , compromised creative intent.













Production Display Brightness
Consumer Display Brightness
Versioning: HDR to SDR grading (tone-mapping)
219

Potential Issues with Bright HDR displays
− Colour shift in the Mesopic-level adaption
• As light moves below Photopic (dominated by cones) and gets closer to Scotopic (dominated by
rods) colour saturation will diminish
• This may occur in dark scenes in low-light home theatres
− Light/Dark Adaption (‘bleaching’ process rather than pupil size)
• Sustained bright images cause the photopigment in the retina to reduce and can result in the
perception of after-images
• Dark adaption can take seconds or even minutes
• Changes from bright to dark scenes may take longer in dark theatre as opposed to same scene in
higher ambient light
220

Potential Issues with Bright HDR displays
− Viewing Distance
• Static adaption is only about 7 to 9 stops
• To take full advantage of HDR (>9 stops) with local adaption, you need to be closer than 2 screen
widths (eye strain risk)
− Large Area Flicker
• Strobing of high peak light levels may cause distress (PSE BT.1702)
• Perceptual flicker frequency may be increased since it is a function of retinal adaption
• Frame rate judder may be more visible
221

Artistic Control for HLG and PQ.
− One challenge to live HDR productions is that an artistic control of the look of the images is requested by
users. A new set of controls have been implemented in the latest HDR-capable cameras which allows
modifying the HLG or PQ curves to achieve a certain look to the image.
222

Artistic Control for HLG and PQ.
− If the specified HDR curve is modified after the output of the camera (which means in the 10-bit domain), it
would reduce the headroom of the signal. Therefore it is important that the HDR workflow selected allows
having these functions inside the camera head where a much larger bit depth is available, preserving the
full native 10-bit HDR performance.
223
Workflow diagram for native HDR operation with artistic control inside the camera head

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