HDR and WCG Principles-Part 5

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

Gamut of a Color Space (Color Gamut)
https://nick-shaw.github.io/cinematiccolor/common-rgb-color-spaces.html 6
• Outside edge defines fully
saturated colours.
• Purple is “impossible”.
• No video, film or printing
technology is able to fill all the
colors can be see by human eye.

– The maximum (“brightest”) and minimum (“darkest”)
values of the three components R, G, B define an
space in CIE 1931 color space known as the “color
space”.
− The Gamut of a color space is the complete range of
colors allowed for a specific color space.
• It is the range of colors allowed for a video signal.
− Each corner of the gamut defines the primary
colours.
Gamut of a Color Space (Color Gamut)
𝑥 + 𝑦 + 𝑧 = 1
𝑥 =
𝑋
𝑋 + 𝑌 + 𝑍
𝑦 =
𝑌
𝑋 + 𝑌 + 𝑍
𝑧 =
𝑍
𝑋 + 𝑌 + 𝑍
BT.2020
7

Gamut of a Color Space (Color Gamut) on WFM
Waveform Monitor
BT.2020
8

𝒙 + 𝒚 + 𝒛 = 𝟏
𝒙 =
𝑿
𝑿 + 𝒀 + 𝒁
𝒚 =
𝒀
𝑿 + 𝒀 + 𝒁
𝒛 =
𝒁
𝑿 + 𝒀 + 𝒁
Color Gamut on WFM
9

ITU-R BT. 601 Color Spaces
– The Rec. 601 color gamut has been
specified in the ITU standard ITU-R BT.601 for
SDTV (Standard Definition Television) as the
first television color space defined for digital
television.
– The Rec. 601 color space, which is very
similar to the HDTV color space Rec. 709,
however, has a slightly different color
triangle.
– While the Rec. 601 color gamut specifies a
few more colors in the green-blue area,
Rec. 709 defines slightly more colors in the
green-red area
10

ITU-R BT. 709 Color Spaces
– The Rec. 709 color space has been
specified in the ITU standard ITU-R BT.709
and is therefore still valid as today’s HDTV
color space.
– Unlike Rec. 601, Rec. 709 specifies slightly
more colors in the green-red area, but
fewer colors in the green-blue area.
11

BT. 601 and BT.709 Color Spaces
– Rec-601 and Rec-709 are basically on top of
each other.
– So, we can use the same screen for SD and
HD (with Rec-709) with out going through
conversion in the Monitor to change the
color space.
12
709 Color Space 601 Color Space
Vector look is same as each other

WCG
Wide Color Space (ITU-R Rec. BT.2020)
75.8%, of CIE 1931
Color Space (ITU-R Rec. BT.709)
35.9%, of CIE 1931
CIE 1931 Color Space
Wide Color Gamut Makes Deeper Colors Available
13
– Deeper Colors
– More Realistic Pictures
– More Colorful

0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
(a) Carnation
x
(b) Geranium and marigold
x
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
c) Sunflower
x
(d) Butterfly
x
14
– Deeper Colors
– More Colorful
75.8%, of CIE 1931
35.9%, of CIE 1931
75.8%, of CIE 1931
35.9%, of CIE 1931

15
– Deeper Colors
– More Colorful
(Inner triangle: HDTV primaries, Outer triangle: UHDTV primaries)
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
(a) Carnation
x
(b) Geranium and marigold
x
75.8%, of CIE 1931
35.9%, of CIE 1931
75.8%, of CIE 1931
35.9%, of CIE 1931

16
– Deeper Colors
– More Colorful
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
c) Sunflower
x
(d) Butterfly
x
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
0 .1 .2 .3 .4 .5 .6 .7 .8
0
.1
.2
.3
.4
.5
.6
.7
.8
y
(e) Model car
x
(f) Stained glass
x
75.8%, of CIE 1931
35.9%, of CIE 1931
75.8%, of CIE 1931
35.9%, of CIE 1931

BT. 2020 Color Space
− By changing the relative positions of the R, G and
B primaries to lie as close as possible to the
spectral locus, while keeping the definition of the
white point intact, BT.2020 is created.
– Rec. 2020 color space covers 75.8%, of CIE 1931
while Rec. 709 covers 35.9%.
Chromaticity coordinates of Rec. 2020 RGB primaries and
the corresponding wavelengths of monochromatic light
Parameter Values
Opto-electronic transfer
characteristics before
non-linear pre-correction
Assumed linear
Primary colours and
reference white
Chromaticity coordinates
(CIE, 1931)
x y
Red primary (R) 0.708 0.292
Green primary (G) 0.170 0.797
Blue primary (B) 0.131 0.046
Reference white (D65) 0.3127 0.3290
𝑥 + 𝑦 + 𝑧 = 1
𝑥 =
𝑋
𝑋 + 𝑌 + 𝑍
𝑦 =
𝑌
𝑋 + 𝑌 + 𝑍
𝑧 =
𝑍
𝑋 + 𝑌 + 𝑍
17

BT.709 Color Space BT.2020 Color Space
18

19

DCI P3 Color Space (SMPTE 431-2), A digital Cinema Color Space
− It stands for Digital Cinema Initiatives – Protocol 3 and
pairs beautifully with 10-bit, 1.07 billion color displays.
− The DCI-P3 color space is an RGB color space that
was introduced by DCI and standardized by SMPTE.
− This color space features a Color Gamut that is much
wider than sRGB.
− All Digital Cinema Projectors are capable of
displaying the DCI-P3 color space in its entirety.
− Wide Color Rec 2020 color, it is 27% wider than P3.
− Note that D65-P3 means that the color temperature of
the white point is set at D65 instead of the “DCI” white
point.
− 4K can use Rec 709, DCI P3, or Rec 2020 with 10 or 12
bits.
𝑥 + 𝑦 + 𝑧 = 1
𝑥 =
𝑋
𝑋 + 𝑌 + 𝑍
𝑦 =
𝑌
𝑋 + 𝑌 + 𝑍
𝑧 =
𝑍
𝑋 + 𝑌 + 𝑍
20

XYZ Color Space
– To emulate rich film-based cinema colors, the XYZ
color space allows for richer colors on digital cinema
applications.
– The CIE 1931 chromaticity diagram was derived from
XYZ color space.
21

Academy Color Encoding System (ACES) Color Space
– File based system
– Method for conversion between range of color spaces
• 33 bit floating point (16-bit, half-floats)
• 10-bit proxy output in stops (log2)
22
SMPTE Reference Projector
Rec. BT.709 ACES
Spectrum Locus
XYZ Color Space
ACES Color Space
CIE x CIE y
Red 0.73470 0.26530
Green 0.00000 1.00000
Blue 0.00010 -0.07700
CIE 2 Degree
Chromaticity Diagram
More Info: https://chrisbrejon.com/cg-cinematography/chapter-1-5-academy-color-encoding-system-aces/

– It is the dynamic range and wide color gamut preserving
workflow, not an HDR format.
– An industry standard for managing color throughout the
life cycle of a motion picture or television production.
– ACES is a free, open, device-independent color
management and image interchange system that can
be applied to almost any current or future workflow.
– ACES solves numerous integration challenges (Ex. images
from different cameras) by enabling consistent, high-
quality color management from production to
distribution.
– ACES ensures a consistent color experience that
preserves the creative vision.
The ACES color
space includes
everything the
human eye can see.
ACES industry standard for color
23

– ACES is a series of color spaces and transforms that allows
you to manipulate them. This standard consists of
• encoding specifications, transform definitions, guidelines
• metadata definitions
• standard screen specifications
• specifications for archive-ready image data and
metadata
– ACES is currently being integrated in many of the
hardware and software tools you already use.
– From capture through editing, VFX, mastering, public
presentation, archiving and future remastering.
– For every type of color management in workflow, from
image capture to distribution (from beginning up to the
end of workflow).
24
The ACES color
space includes
everything the
human eye can see.
ACES industry standard for color

25
https://www.youtube.com/watch?v=DX5tQix9NbY&t=96s

Here is a list of the five ACES color spaces:
• ACES 2065-1 is scene linear with AP0 primaries. It remains the core of ACES
and is the only interchange and archival format (for Digital Cinema
Distribution Master (DCDM)).
• ACEScg is scene linear with AP1 primaries (the smaller “working” color
space for Computer Graphics).
• ACEScc, ACEScct and ACESproxy all have AP1 primaries and their own
specified logarithmic transfer functions.
26
AP0 is defined as the smallest set of primaries that
encloses the whole CIE 1964 standard-observer
spectral locus; thus theoretically including, and
exceeding, all the color stimuli that can be seen by
the average human eye.
AP1 primaries are nearer the spectral locus, and are
closer to traditional grading primaries than are the AP0
primaries.

ACES is composed of three main processes described in the following image:
• A. IDT (Input Device Transform) is the import/conversion of the images to the ACEScg color space.
• B. ACEScg is the rendering/working space.
• C. RRT (Reference Rendering Transform) + ODT (Output Device Transform) are the Output Transform to any
monitor or video projector.
27

Sony S-Gamute3
(Production Format)
29

Chromaticity Coordinates and Corresponding Wavelengths of
Monochromatic Light
30

CIE XY Coordinates for Various Color Gamut
Monochromatic Light
𝑥 + 𝑦 + 𝑧 = 1
𝑥 =
𝑋
𝑋 + 𝑌 + 𝑍
𝑦 =
𝑌
𝑋 + 𝑌 + 𝑍
𝑧 =
𝑍
𝑋 + 𝑌 + 𝑍
31

𝑥 + 𝑦 + 𝑧 = 1
𝑥 =
𝑋
𝑋 + 𝑌 + 𝑍
𝑦 =
𝑌
𝑋 + 𝑌 + 𝑍
𝑧 =
𝑍
𝑋 + 𝑌 + 𝑍
PAL/SECAM and NTSC Color Gamut's
Monochromatic Light
32

CIE x CIE y
Red 0.708 0.292
Green 0.170 0.797
Blue 0.131 0.046
White 0.3127 0.3290
ITU-R BT.2020
CIE x CIE y
Red 0.640 0.330
Green 0.300 0.600
Blue 0.150 0.060
White 0.3127 0.3290
ITU 709-5 & sRGB Gamut
CIE x CIE y
Red 0.630 0.340
Green 0.310 0.595
Blue 0.155 0.070
White 0.3127 0.3290
ITU 601 Gamut
Monochromatic Light
33

CIE XY Coordinates for Various Color Gamut
CIE several standard white points sources illuminant values
Component Video Values and Gamut
A color gamut range is bounded by the xy coordinates of the primary red, green, and blue colors within
the color space. The xy coordinates for these primary colors is given in the table. 34

Component Video Values and Gamut
35

SD BT.601 and HD BT.709 Vectors
36

BT.2020 and BT.709 Vectors
37
Graticule setting: 709 Color Space
Graticule setting: 2020 Color Space

Standard Definition100% color bar test pattern.
Standard Definition (SD) 100% color bar RGB parade
Standard Definition (SD) 100% color bar YPbPr parade
High Definition (HD) 100% color bar YPbPr parade
Why small Spikes in the RGB waveform parade? This is due to
• the unequal rise time between Luma and Color
Difference bandwidths and
• the conversion of SDI Y'P'bP'r back to R'G'B' in the
waveform display.
38
Different Equations ⇒ Different Levels for each of the Component Signals

HD 100% color bars YPbPr parade, Rec. 709. UHD 100% color bars YPbPr parade, Rec. 709.
• Spike transitions is normal because no video filtering is applied to each link.
• This allows the quad links to be seamlessly stitched together, otherwise a
thin black line would be seen between the links. 39
HD signal and UHD signal in BT.709 Color Space

You can compare the difference in levels between Rec. 709 and Rec. 2020.
40
UHD signal in BT.709 and BT.2020 Color Spaces
UHD 100% color bars YPbPr parade, Rec. 709. UHD 100% Color Bars YPbPr parade, Rec. 2020.

UHD 100% Split Field Color Bars with both 709 and 2020 color spaces in YPbPr Parade display.
41
By overlapping two previous figures, is obvious
that here are slight difference in the video levels
UHD signal in BT.709 and BT.2020 Color Spaces

 In some cases the SMPTE 352 VPID may contain information on the
colorimetry data that is used. Often however, this may not be the case
and a known test signal such as color bars will be necessary to assist the
user in determining the correct color space.
 The user must manually select from the configuration menu between the
709 and 2020 colorspaces.
42
UHD 100% Split Field Color Bars with both 709 and 2020 color spaces in RGB Parade display.
UHD signal in BT.709 and BT.2020 Color Spaces, SMPTE 352 VPID
When the correct colorspace is selected then the
traces will be at 0% and 100% (700mv) levels.

43

44
YPbPr View RGB View
YRGB View Composite View
Common Different Waveform Monitor Views

Y Cb Cr
45
Common Different Waveform Monitor Views

46
Maximum
Gamut
Minimum
Gamut
Gamut Monitoring - the Traditional Way RGB Domain
The maximum (“brightest”)
and minimum (“darkest”)
values of the three
components R, G, B define
“color gamut”.

Legal/Illegal Signal
47
A Legal/Illegal Signal
− A signal is legal if it stays within the gamut appropriate for the format in use.
− A legal signal stays within the voltage limits specified for all signal channels
for a given format (it does not exceed the voltage limits specified for the
format of any signal channel).
− An illegal signal is one that is, at some time, outside the limits in one or
more channels.
− A signal can be legal but still not be valid.
 The allowed range for R'G'B' channels and Y‘C'bC'r ' channels
• 0 to 700 mV
 The allowed ranges for Y'P'bP'r
• 0 to 700 mV for the luma (Y') channel
• ±350 mV for the color difference (P'b/P'r) channels
700 mV
0 mV
700 mV
0 mV
700 mV
0 mV
R
G
B

48
A signal can be legal in one color space but not legal when converted to another
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Converted back
to RGB
D Illegal
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Distorted
Color Difference
C Legal
Legal RGB
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
A
Legal/Illegal Signal

Valid Color Gamut
− It is defined as all colors represented by all
possible combinations of legal values of an
R'G'B' signal.
− Signals in other formats (YUV, YCrCb, …) may
represent colors outside valid gamut, but still
remain within their legal limits.
− These signals, when transcoded to the R'G'B'
domain, will fall outside legal R'G'B' limits.
− This may lead to clipping, crosstalk, or other
distortions.
Valid Color Gamut
49
(Valid color gamut for YCrCb)
Inside Valid
Gamut
Outside Valid
Gamut
Outside Valid
Gamut
RGB Colors Cube in the YCbCr Space

Legal Signal and Valid Signals
50
A Valid Signal
− A video signal where all colors represented lie
within the valid color gamut.
− For YCbCr, it means all Y, Cb and Cr signals that
falls into valid color gamut of YCbCr color space.
− A valid signal will remain legal when translated to
R'G'B' or other formats.
− A valid signal is always legal, but a legal signal is
not necessarily valid.
− Signals that are not valid will be processed
without problems in their current format, but may
encounter problems when translated to another
format.
RGB Colors Cube in the YCbCr Space
(Valid color gamut for YCrCb)
Legal Signal
Valid Signal
Legal Signal
Invalid Signal
Illegal Signal
Invalid Signal

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.
51
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.
52
This percentage are used just in narrow range.

− An incorrect interpretation of the video range values used in SDI links and compression technologies for
contribution and distribution can seriously compromise the images.
− Any signals that contain values that exceed the total video signal range will be clipped (application-
specific).
− Such clipping can cause harmonic distortion and alias artefacts in the video signal, which manifests as
compression artefacts and the potential for increased data rates both for contribution and distribution.
53
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

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).
− When television signals are manipulated in YUV form, it is possible to produce "illegal" combinations that, when de-
matrixed, would produce R, G or B signals outside the range 0% - 100%.
HDR to SDR Color Volume Conversion
− It is expected that some colours that are present in the HDR colour volume when converted to SDR will be outside of the
ITU-R BT.709 volume Nominal Range but within the Preferred Range.
− This allows conversion processing to maintain the saturation and brightness of colours already within the Nominal Range
target colour volume.
54
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

Video Signal Tolerance
− In practice it is difficult to avoid generating signals slightly out of range, and it is considered reasonable to allow a small
tolerance.
− Therefore, 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.
55
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

Out-of-Gamut
− The term “Out-of-Gamut” refers to code values that exceed the Preferred Min / Max
values in the table.
− Certain operations and signal processing may produce relatively benign gamut
overshoot errors in the picture.
− Therefore, the EBU further recommends that measuring equipment should indicate
an “Out-of-Gamut” occurrence only after the error exceeds 1% of the image.
(signals outside the active picture area shall be excluded from measurement).
− Experience has shown that colour gamut "legalisers" should be used with caution as
they may create artefacts in the picture that are more disturbing than the gamut
errors they are attempting to correct.
− It is advisable not to “legalise” video signals before all signal processing has been
carried out.
56

− Color Space / Dynamic Range / Gamma Comparison (Side by Side, Wipe position) allows users to compare different
color spaces, gammas, HDR / SDR, camera logs, and other color settings side by side simultaneously.
− The comparison area can be selected and moved with a vertical wipe pattern.
Example: Postium OBM-X Series Overview
57

− False Color indicates the Luma (Y) level of the input image.
− If a certain Y level is set, the pixels with the designated Luma (Y) level are displayed with a zebra pattern or a color
pattern. There are display modes – Zebra, Variable, ARRI, and Comparison.
58

− Gamut Error Type can be observed in 3 modes.
− In Type 1, when the targeted color space is selected
as BT.709, the pixels outside of the targeted color
space are displayed as Black Zebra.
− The pixels over Y Maximum, Chroma Maximum, RGB
Maximum are displayed as Black Zebra, and the
pixels below Y Minimum, Chroma Minimum, RGB
Minimum are also displayed as Black Zebra.
59
Y Maximum, Chroma Maximum, RGB Maximum
Y Minimum, Chroma Minimum, RGB Minimum

− In Type 2, when the targeted color space is selected
as BT.709, the pixels outside of the targeted color
space are displayed as Black or White Zebra.
− The pixels over Y Maximum, Chroma Maximum, RGB
Maximum are displayed as Black Zebra, and the
pixels below Y Minimum, Chroma Minimum, RGB
Minimum are displayed as White Zebra.
60

− In Type 3: Mono, when the targeted color space is
selected as BT.709, the pixels inside of the targeted
color space are displayed as Mono, and the pixels
outside of the targeted color space are displayed as
the color.
− In this type, black and white area is not recognized.
61

− SDR/HDR Display modes provide both full-frame HDR and SDR viewing as well as simultaneous side-by-side split screen
comparison.
− 4K HDR Waveform Monitor and Vector Scope Display modes enable users to monitor sources using the internal
Waveform and Vector Scope individually or simultaneously.
62
HDR Waveform
SDR Waveform
HDR Display modes + HDR Waveform
SDR Display modes + SDR Waveform

− OBM-X series has Built-in Camera Log to Linear conversion LUTs from various camera manufacturers including Log-C, C-Log /
S-Log2, S-Log3 / J-Log1 and more.
− The LUT-converted content can then be output to downstream devices/monitors via the SDI loop out.
63

Video Levels
Digital 10- and 12-bit Integer Representation (ITU-R BT.2100-2)
Round( x ) = Sign( x ) * Floor( | x | + 0.5 )
Floor( x ) the largest integer less than or equal to x
Resulting values that exceed the
video data range should be
clipped to the video data range
Narrow Range
𝑫 = 𝑹𝒐𝒖𝒏𝒅 [(𝟐𝟏𝟗𝑬′
+ 𝟏𝟔) × 𝟐𝒏−𝟖
)]
𝑫 = 𝑹𝒐𝒖𝒏𝒅 [(𝟐𝟐𝟒𝑬′
+ 𝟏𝟐𝟖) × 𝟐𝒏−𝟖
)]
Full Range
𝑫 = 𝑹𝒐𝒖𝒏𝒅 [(𝟐𝒏
− 𝟏)𝑬′
]
𝑫 = 𝑹𝒐𝒖𝒏𝒅 [ 𝟐𝒏
− 𝟏 𝑬′
+ 𝟐𝒏−𝟏
)]
Coding 10-bit 12-bit 10-bit 12-bit
Black
(R' = G' = B' = Y' = I = 0)
DR', DG', DB', DY', DI
64 256 0 0
Nominal Peak
(R' = G' = B' = Y' = I = 1)
DR', DG', DB', DY', DI
940 3760 1023 4095
Nominal Peak
(C'B = C'R = -0.5)
DC'B, DC'R, DCT, DCP
64 256 0 0
Achromatic
(C'B = C'R = 0)
512 2048 512 2048
Nominal Peak
(C'B = C'R = +0.5)
960 3840 1023 4095
Video Data Range 4~1019 16~4079 0~1023 0~4095
64

Code Values for Rec-709, DCI-P3, Rec-2020
– SDI digital code values for R,G,B primaries are the same for all spaces (Rec-709, Rec-2020, DCI-P3).
• R,G,B primaries of a generator or any other output is exactly the same for Rec-709, Rec-2020, DCI-P3
Color spaces.
– Translation between SDR and HDR will scale the colors.
– Translation between color spaces in SDR space will expand the colors due to the fact that they use the
same code values.
3ACh
(Narrow) or
3FBh (Full)
3ACh
(Narrow) or
3FBh (Full)
3ACh
(Narrow) or
3FBh (Full)
Rec-709 DCI-P3 Rec-2020
65

Same RGB (SDI) -Different Displays
It’s the receiver that determines what the code value means.
66

CIE Rec 2020 Chart with a Rec 709 Signal Applied
– It’s the receiver that determines what the code value means.
– Just changing the receivers interpretation, just moves the signal to that point.
– On the SDI signal 100% green is 100% green for all colors spaces.
67

Reference: High Dynamic Range Video From Acquisition to Display and Applications
What is a “3D Color Volume”?
68

2D Chromaticity Diagram 3D Color Volume
W
100
50
0
x
R
Y
C
G
B
Y
in
%
3D Color Volume(xY Viewpoint)
What is a “3D Color Volume”?
69

© 2015 Society of Motion Picture and Television Engineers (SMPTE)
Benefits of a Large Color Volume
Expanded to
R2020/1000cd/m²
Color Volume
Limited to R709/100cd/m²
Color Volume
70

Benefits of a Large Color Volume
Expanded to
R2020/1000cd/m²
Color Volume
Limited to R709/100cd/m²
Color Volume
71

High Dynamic Range - Slim, Wide, Tall Volumes
TV System ITU Standard Image Size Color Volume
HD BT.709 1920×1080 “2K” Slim (SDR)
UHD 1 BT.2020 3840×2160 “4K” Slim (SDR) or Wide (WCG)
UHD 2 BT.2020 7680×4320 “8K” Slim (SDR) or Wide (WCG)
HDR BT.2100 2K, 4K, 8K Wide (WCG) & Tall (HDR)
Slim
Wide
40% wider Saturated colors
High dynamic range
10-100x brighter peaks
100x darker than SDR
Wide &Tall
72

HDR Brightness Range & Gamut
Brighter
Darker
More Colorful
HDR
HDR Media Color Volume
HDR Display Color Volume
HDR Media Color Volume
is much larger than
HDR Display Color Volume
73

Color Gamut Conversion (Gamut Mapping and Inverse Mapping)
A
1
B C
2
D
3
RGB 100% Color Bar View with
Rec. 709
Rec. 2020
CIE 1931 Color Space
74
75.8%, of CIE 1931
35.9%, of CIE 1931

A
1
Munsell
Chart
75
BT.2020 Signal BT.709
Transformation from a Wider Gamut Space to a Smaller One
(ITU-R Rec. BT.2020)
(ITU-R Rec. BT.709)

Munsell
Chart
A
1
Three Approaches:
• Clipping the RGB values to the allowed range (in ITU-R BT.709) at the cost of introducing clipping distortions.
• Applying perceptual gamut mapping at the cost of more computations and possibly changing the ‘creative intent’.
• Leaving the RGB values as they are - relative contributions of ITU-R BT.2020 primaries - and let the screen think that they
relate to primaries of ITU-R BT.709.
Without any corrections (lack of proper gamut mapping), since the original color components represent contributions
of ‘wider primaries’, displaying these values using ‘narrower primaries’ will make the image appear less saturated.
76
(ITU-R Rec. BT.709)

− Going from the larger to the smaller can be more complicated
• A hue shift should really be avoided.
• Colors are remapped along the vector towards the origin to
the point they are legal.
• This means that ALL colors on that vector outside of the
smaller space (BT. 709), become the same.
In the end, the visible differences to viewers are likely to be
fairly subtle (non obvious) and the standard return vs. effort
decisions will need to be done.
These are Artistic Choices!
Where does the
point map to?
77

D
3
Munsell
Chart
78
Transformation from a Smaller Gamut Space to a Wider One
(ITU-R Rec. BT.709)

D
3
Without any corrections on BT.709 (lack of proper gamut
mapping), on a BT.2020 display color saturation will be increased.
Munsell
Chart
79
(ITU-R Rec. BT.709)

− Going from the smaller to the larger is mostly straightforward
• Simple approach is to simply convert pixel by pixel values
which leaves smaller to the ‘extra’ space
• You may have desire Artistic choices to ‘stretch’ a portion of
the pixels near the boundaries into the ‘extra’ space
• We can desaturation a color until it is within the smaller color
space, because the larger color space hasn’t invented new
hues, it has allowed us to show more vibrant colors than we
could before.
Where does the
point map to?
80

Definitions:
– A Rec. 709 display is a display device with RGB primaries that correspond to those in Recommendation
ITU-R BT.709, a D65 white point, and an EOTF which conforms to Recommendation ITU-R BT.1886.
– A Rec. 2020 display is a display device with RGB primaries that correspond to those in Recommendation
ITU-R BT.2020, a D65 white point, and an EOTF which conforms to Recommendation ITU-R BT.1886.
Recommendation ITU-R BT.2087-0 (10/2015)
81
(ITU-R Rec. BT.709)

Definitions:
– A concept of signal flow from scene light to display light in video systems is modelled as shown in the
figure ure, consisting of four functions. Camera adjustments include linear segment near black, pre-knee,
knee point, knee slope, and other adjustments.
– The Rec. 709 and Rec. 2020 OETFs are similar to a square root function.
• The deviation of these OETFs from a 1/2.0-power function including the linear segment near black can be
decomposed into the camera adjustment function. So the OETF itself can be regarded as a square root function.
• On the basis of this concept, the square function and square root function should be used for the conversion
between linear and non-linear signal representations.
82
Camera
Adjustments for
Creative Rendering
Opto-electronic
Transfer Function
(OETF)
electro-optical
transfer function
(EOTF)
Display Adjustments
to Compensate for
Viewing Environment
Image
Data
Scene Light Display Light
Linear to non-linear conversion
Non-linear to Linear conversion

Colour conversion from Recommendation ITU-R BT.709 to Recommendation ITU-R BT.2020
– Figure shows a block diagram of the colour conversion from Recommendation ITU-R BT.709 (Rec. 709) to
the non-constant luminance signal format of Recommendation ITU-R BT.2020 (Rec. 2020).
– The input and output of this diagram are digitally represented Y′C′BC′R signals or R′G′B′ signals.
83
(ITU-R Rec. BT.709) (ITU-R Rec. BT.2020)
Non-constant
Luminance Signal

84
Inverse-quantisation of digitally represented luminance and colour-difference
signals D′YD′CBD′CR (Rec. 709) in the bit-depth of N709 bits to normalized luminance
and colour-difference signals E′YE′CBE′CR (Rec. 709):
Inverse-quantisation of digitally represented colour signals
D′RD′GD′B (Rec. 709) in the bit-depth of N709 bits to
normalized colour signals E′RE′GE′B (Rec. 709):
Conversion from normalized luminance and colour-difference signals E′YE′CBE′CR
(Rec. 709) to normalized R′G′B′ colour signals E′RE′GE′B (Rec. 709):

85
Non-linear to linear conversion from normalized R′G′B′ colour signals E′RE′GE′B (Rec. 709) to linearly represented, normalized RGB colour signals EREGEB (Rec.
709) is accomplished by one of two equations which produce slightly different colours from each other:
Case #1: In the case where the goal is to preserve colours seen on a Rec. 709 display when displayed on a Rec. 2020 display, an
approximation of the electro-optical transfer function (EOTF) from Recommendation ITU-R BT.1886 (Rec. 1886) is used:
Case #2: In the case where the source is a direct camera output and the goal is to match the colours of a direct Rec. 2020
camera output, an approximation of the Rec. 709 inverse opto-electronic transfer function (OETF) is used:
NOTE – E and E' are defined within the range of 0 to 1 in Recommendation ITU-R BT.709. However, the definition of the video signal quantization allows values
above 1 or below 0. The above equation may also be applied to those values above 1 or below 0 with an appropriate treatment of the sign for negative values.

86
Colour conversion from linearly represented, normalized RGB colour
signals EREGEB (Rec. 709) to linearly represented, normalized RGB colour
signals EREGEB (Rec. 2020) (All matrix values above were calculated with
high precision and then rounded to four decimal digits.):
Linear to non-linear conversion from linearly represented, normalized RGB colour signals EREGEB (Rec. 2020) to normalized R′G′B′
colour signals E′RE′GE′B (Rec. 2020) is accomplished by applying the inverse of the non-linear to linear conversion equation.
Case #1: In the cases where the goal is to preserve colours seen on a Rec. 709 display, an approximation of the inverse of Rec.
1886 EOTF is used:
camera output, an approximation of the Rec. 2020 OETF is used:

87
Conversion from normalized R′G′B′ colour signals E′RE′GE′B (Rec. 2020) to normalized
luminance and colour-difference signals E′YE′CBE′CR (Rec. 2020):
Quantisation of normalized colour signals E′RE′GE′B (Rec. 2020) to digitally
represented colour signals D′RD′GD′B (Rec. 2020) in the bit-depth of N2020 bits:
Quantisation of normalized luminance and colour-difference signals
E′YE′CBE′CR (Rec. 2020) to digitally represented luminance and colour-
difference signals D′YD′CBD′CR (Rec. 2020) in the bit-depth of N2020 bits:

Colour conversion from Recommendation ITU-R BT.709 to Recommendation ITU-R BT.2020
– Figure shows a block diagram for the colour conversion from Rec. 709 to the constant luminance signal format of
Recommendation BT.2020. The input signals of this diagram are digitally represented R′G′B′ and Y′C′BC′R.
– And the output signals are digitally represented R′G′B′ and Y′CC′BCC′RC where the addition of the ‘c’ subscript indicates
the constant luminance signal format.
– To differentiate between the non-constant and constant signal format, the ‘c’ subscript is added for the constant
luminance signal format.
88
Constant Luminance Signal
(ITU-R Rec. BT.709)

89
For the five blocks inside the black broken line, the same equations and input/output signals are applied as in the descriptions for previous figure.
These blocks correspond to the conversion from the digitally represented luminance and colour-difference D′YD′CBD′CR and colour D′RD′GD′B signals (Rec. 709) to
the linearly represented, normalized RGB colour signals EREGEB (Rec. 2020).
Conversion from linearly represented, normalized
RGB colour signals EREGEB (Rec. 2020) to normalized
constant-luminance signal EYc (Rec. 2020):

90
Linear to non-linear conversion from linearly represented, normalized RB colour signals EREB and normalized constant-luminance signal EYc (Rec. 2020) to non-
linearly represented, normalized R′B′ colour signals E′RE′B and normalized constant-luminance signal E′Yc (Rec. 2020) is accomplished by applying the inverse of
the non-linear to linear conversion equation.
Case #1: In the case where the goal is to preserve colours seen on a Rec. 709 display when displayed on a Rec. 2020 display, an
approximation of the Rec. 1886 inverse EOTF is used:
camera output, an approximation of the Rec. 2020 OETF is used :

91
Conversion from non-linearly represented, normalized R′B′ colour signals E′RE′B and normalized constant-
luminance signal E′Yc (Rec. 2020) to normalized colour-difference signals E′CBcE′CRc (Rec. 2020):
Quantisation of normalized colour signals E′RE′GE′B
(Rec. 2020) to digitally represented colour signals
D′RD′GD′B (Rec. 2020) in the bit-depth of N2020 bits:
Quantisation of normalized constant-luminance and colour-difference signals
E′YcE′CBcE′CRc (Rec. 2020) to digitally represented constant-luminance and colour-
difference signals D′YcD′CBcD′CRc (Rec. 2020) in the bit-depth of N2020 bits:

Colour Gamut Conversion from Recommendation ITU-R BT.2020 to Recommendation ITU-R BT.709
– It addresses in general the following goals:
1. To advise on the advantages and disadvantages of automatic conversion techniques and to seek to identify
optimum conversion mechanisms.
2. To advise on any additional measures that may be appropriate in order to achieve optimum colour gamut
conversion and avoiding the introduction of subjectively disturbing artefacts.
3. To investigate a possible method of colorimetry conversion from ITU-R BT.2020 (BT.2020) to ITU-R BT.709 (BT.709) in
terms of image quality and feasibility that ideally satisfies the following requirements:
• Colours inside the BT.709 gamut should be unchanged.
• The conversion method should facilitate multiple conversions between BT.2020 and BT.709.
• Perceived hue change must be as small as possible.
• No significant loss of spatial details.
• Will not introduce visible discontinuities in colour.
• The mapping method is mathematically definable.
Report ITU-R BT.2407 (2017)
92
There is no universal gamut
mapping method which can
achieve all of these
requirements simultaneously.
⇒
(ITU-R Rec. BT.709)

Colour Gamut Conversion from Recommendation ITU-R BT.2020 to Recommendation ITU-R BT.709
– There is no universal gamut mapping method which can achieve all of these requirements simultaneously.
– In converting from a wider colour gamut to a smaller colour gamut, modification of colours outside the
BT.709 gamut is unavoidable.
– This conversion is necessarily a compromise between different requirements which may vary depending
on the application.
– Gamut mapping algorithms are often motivated by aspects of artistic creation, human vision, technical
constraints and experience.
– Metrics for identifying colour gamut conversion performance have not yet been developed along with an
associated suite of tests.
93
(ITU-R Rec. BT.709)

Principles of gamut mapping
– To improve upon the results of simple linear matrix transformation with hard-clipping, a well-designed
gamut mapping process may be performed.
– Figure shows a diagram of a general gamut mapping algorithm from BT.2020 to BT.709.
– The input BT.2020 RGB signals are converted to the coordinates of a selected mapping colour space, then
the colours within the ITU-R BT.2020 colour gamut are mapped to colours within the BT.709 colour gamut
based on a gamut mapping algorithm.
– The gamut-mapped colours are then converted to the output BT.709 RGB signals.
94
RGB to Mapping
Colour Space
Colour Gamut
Mapping
Mapping Colour
Space to RGB
BT.2020 BT.709
CIE xyY, CIE u’v’Y, CIE L*a*b*, …

– The selection of mapping colour space is a crucial aspect to conversion. Some of the different mapping
colour spaces that may be used are:
• CIE xyY
• CIE u’v’Y
• CIE L*a*b*
• Simplified Lab
• Uniform colour space based on CIECAM02
95
RGB to Mapping
Colour Space
Colour Gamut
Mapping
Mapping Colour
Space to RGB
BT.2020 BT.709
CIE xyY, CIE u’v’Y, CIE L*a*b*, …

• In the CIE xyY and u’v’Y colour spaces, linear colour mixing holds.
• BT.2020 or BT.709 RGB (𝐸𝑅𝐸𝐺𝐸𝐵) values can be linearly converted to the CIE xyY
and u’v’Y coordinates by simple linear and projective operators.
• Chromaticity is a representation of the ratio of each set of three tristimulus
coordinates values to their sum.
• The xy plane is the traditional representation of chromaticity, while the u’v’
chromaticity plane has the advantage of being perceptually more uniform
than the xy plane when Y is constant.
• When using xyY or u’v’Y mapping colour spaces, designing gamut mapping
algorithms can be expected to be simpler by utilizing linear transforms.
• However, if a mapping path ‒used to map a colour from BT.2020 colour
gamut to BT.709 colour gamut‒ is straight, perceived lightness, chroma and
hue of colours may change simultaneously. 96
CIE L*u*v*
L=0
CIE xyY
Y=0

• The CIE L*a*b* colour space was designed to have a better visual uniformity than xyY or u’v’Y colour
spaces. The Simplified Lab colour space is a simplification of the CIE L*a*b* colour space in which colour
gamuts have simpler shapes with approximately plane surfaces.
• The CIE L*a*b* and simplified Lab colour spaces require more complex, non-linear operations to derive
them from BT.2020 or BT.709 (𝐸𝑅𝐸𝐺𝐸𝐵) values.
 One advantage of these colour spaces is their perceptual uniformity that takes lightness into account; Euclidean
distances in the three-dimensional colour space are nominally proportional to the perceived colour differences.
 Another advantage is that the colour spaces have the cylindrical coordinates L*C*h* or simplified LSCShS
corresponding to perceptual lightness, chroma, and hue, respectively. If a source colour is mapped to a target
colour having the same metric hue angle h or hS, the perceived hue can be expected to be the same.
 When using CIE L*a*b* or simplified Lab colour spaces, linear mapping paths may preserve one or two of
lightness, chroma, and hue. Along these mapping paths, source colours from BT.2020 are moved to BT.709
target colours. This modification of colours may involve linear or non-linear functions.
97

• CIECAM02 established by CIE Technical Committee 1-34 has an advantage in the prediction of blue hue.
• The significant non-uniformity of the CIE L*a*b* metric blue hue is improved.
• Some gamut mapping methods preserve all of the colours inside the BT.709 gamut while the other
methods modify some colours within the BT.709 gamut, especially those near the BT.709 gamut boundary.
• This modification of colours within the BT.709 colour gamut can cause significant artefacts when multiple
round trip conversions are performed.
• It should be noted that through the use of metadata or content analysis, the content colour gamut,
defined as the actual distribution of colours in a programme or scene, may be determined.
• Since the content colour gamut is often much smaller than the total BT.2020 colour gamut, the amount of
required colour gamut compression is reduced with an accompanying reduction in distortions.
• Note that this additional information is not dependent on a specific algorithm, i.e. the result of any
algorithm could be improved by using content colour gamut.
98

Different Approaches Specifications
• Many techniques exist to perform gamut mapping, utilizing many different combinations of the tools
described above.
• It has proven impossible to select just one method as the single, best option for performing BT.2020 to
BT.709 video conversions.
99
• The six Annexes to this Report detail
some examples of advanced gamut
mapping systems, and are included
as background information to help
readers in their understanding of what
kinds of options may be available in
the industry.
• The table is provided to help compare
the design goals and characteristics
of the mapping methods found in the
Annexes of Report ITU-R BT.2407.

• Functional Simplicity: Was the mapping method deliberately constructed using only simple functional elements, such as
low complexity colour space conversions, low complexity mapping techniques, or other simplified characteristics? Note
that functional simplicity does not necessarily impact implementation complexity as all of these mapping methods would
likely utilize a 3D look up table in hardware, thereby eliminating any complexity differences in implementation.
• Colour Appearance Space: Within which colour appearance space is the gamut mapping performed?
• Hue Mapping: Does the mapping method modify hues of colours?
• Lightness Mapping: Does the mapping method modify lightness of colours?
100

• Parametric Construction: Is the mapping method constructed using a design that contains adjustable parameters which
allow tuning of the mapping details?
• Reversible Operation: Is the mapping potentially method reversible, such that though an inverse operation, the original
BT.2020 image may be fully reconstructed from the BT.709 mapped result?
• Roundtrip Possible with BT.2087: Is the mapping method constructed such that multiple roundtrips with BT.2087 will not lead
to continuously degrading content (after the initial limiting to the BT.709 gamut)?
• Considers Content Colour Gamut: Can the mapping method take advantage of knowledge that the content does not fill
the entire BT.2020 gamut? This knowledge could come through analysis, from metadata provided by the source, or by
design of the algorithm.
101

Simple conversion from BT.2020 to BT.709 based on linear matrix transformation
– This is the exact inverse of the operation specified in Recommendation ITU-R BT.2087 for conversion from
BT.709 to BT.2020, except that the output signals are hard-clipped.
– This method is the most straightforward and implementable in the least amount of hardware.
– The gain is set so that 75% HLG corresponds to 100% SDR.
• Note other methods may result in different signal levels for input signals outside of the BT.709 colour volume.
102
(ITU-R Rec. BT.709)

Non-linear to linear conversion (N to L)
– The conversion from normalized non-linear RGB signals (𝐸′𝑅 𝐸′𝐺 𝐸′𝐵 ) to normalized linear RGB signals (𝐸𝑅 𝐸𝐺
𝐸𝐵) is calculated using one of the two non-linear to linear transfer functions specified in Recommendation
ITU-R BT.2087.
– There are two cases described in Recommendation ITU-R BT.2087
• one for the Display-referred approach using an electro-optical transfer function (EOTF)
• one for the Scene-referred approach using an inverse OETF
103
(ITU-R Rec. BT.709)

Matrix (M)
– BT.2020 RGB signals are transformed to BT.709 RGB signals using the following equations:
– All values in the matrices were calculated with high precision and then rounded to four decimal digits.
104
(ITU-R Rec. BT.709)

Linear to non-linear conversion (L to N)
– The conversion from normalized linear RGB signals (𝐸𝑅 𝐸𝐺 𝐸𝐵) to normalized non-linear RGB signals (𝐸′𝑅 𝐸′𝐺
𝐸′𝐵) is calculated using one of the two linear to non-linear transfer functions specified in Recommendation
ITU-R BT.2087.
– There are two cases described in Recommendation ITU-R BT.2087
• one for the Display-referred approach using an inverse EOTF
• one for the Scene-referred approach using an OETF.
105
(ITU-R Rec. BT.709)

Practical limitations
– This method has the very desirable property that it does not alter colours within the BT.709 gamut, even
after multiple conversions between BT.2020 and BT.709.
– However, colours outside the BT.709 gamut are hard-clipped, i.e. RGB signals (𝐸𝑅 𝐸𝐺 𝐸𝐵) that are less than
zero or greater than one are clipped to zero or one, which can lead to significant hue shifts and loss of
spatial detail.
– Most content will look just fine, but these artefacts can conflict with the requirements for hue and spatial
detail preservation.
106
(ITU-R Rec. BT.709)

Hardware Colour Matrix Compensation
− Many of the existing hardware devices assume BT.709 colorimetry when converting between R′G′B′ and
Y′C′BC′R signal formats.
− Where it is not possible to configure a device for BT.2100 colorimetry, a correction needs to be applied
elsewhere.
− This might be in the conversion matrix on the complementary interface at the other end of the link (e.g.
within a display) or, as illustrated in the figure , within a look-up table performing a format conversion.
Y'C'BC'R to
R'G'B' using
BT.709
matrix
R'G'B' to
Y'C'BC'R
using
BT.709
matrix (via
LUT)
Y'C'BC'R to
R'G'B' using
BT.2100
matrix (via
LUT)
PQ to HLG
transformation
R'G'B' to
Y'C'BC'R
using
BT.2100
matrix (via
LUT)
Y'C'BC'R to
R'G'B' using
BT.709
matrix (via
LUT)
Y'C'BC'R to
R'G'B' using
BT.709
matrix
Y'C'BC'R
BT.2100
signal
Y'C'BC'R
BT.2100
signal
LUT Processing
Example of colour matrix compensation within a LUT
107

Format Conversion in HDR Production, ITU-R Report BT.2408
Direct-mapping (mapping)
− Direct-mapping refers to the process of simply placing SDR content into an HDR signal container, at the
correct signal level.
• Typically 100% SDR > “HDR Reference White”, 75% HLG signal
Up-mapping
− Up-mapping is similar to direct mapping but SDR highlights given a small 'boost’ to better match the
appearance of a native HDR signals.
Down-mapping
− Down-mapping is the opposite of up-mapping. HDR signals converted to SDR by compressing the HDR
signal highlights.
Hard-clipping (less common)
− It can also be used for HDR to SDR conversion. Can deliver brighter SDR images and graphics, but any
highlights captured by HDR cameras are clipped.
• Down-mapping (tone-mapping) when converting to SDR, rather than hard clipping, will allow the SDR output to
benefit from the high dynamic range production by preserving some detail in the image highlights.
109

HDR HDR
SDR SDR
HDR HDR
SDR SDR
110
SDR to HDR Direct Mapping (Mapping) and Inverse Tone Mapping (Up-mapping)

– SDR content may either be directly mapped or inverse tone mapped (ITM) (up-mapped) into an HDR
format for inclusion in HDR programmes.
111
HDR Signal
SDR Content
(BT.709 or BT.2020)
(Without Expanded
Luminance Range)
Preserved SDR Look
in HDR Program (Ex:20%)
HDR BT.2020 Display
HDR Signal
SDR Content
(BT.709 or BT.2020)
(With Expanded
Luminance Range)
HDR Look
in HDR Program
HDR BT.2020 Display
SDR to HDR Direct Mapping (Mapping) and Inverse Tone Mapping (Up-mapping)

Tone Mapping (TM) (Down-conversion): converting HDR content to an SDR signal range
• Limiting Luminance Range (Compression of the image dynamic range of content)
Inverse Tone Mapping (ITM) (Up-conversion): placing SDR content in an HDR signal with expanded
luminance range and thereby leverage the display capabilities to emulate an HDR look
• Expanding Luminance Range (Expansion of the image dynamic range of content.)
Tone Mapping and Inverse Tone Mapping
SDR Signal
(BT.709 or BT.2020)
SDR Display
(BT.709 or BT.2020)
HDR Signal
(BT.2020) SDR
HDR Display
(BT.2020)
SDR Signal
(BT.709 or BT.2020) HDR
HDR Signal
(BT.2020)
112

113
Display-referred and Scene-referred Conversation
• Display Light Mapping tends to preserve the look created by the transfer characteristic used by the display
(plus artistic intent)
• Scene Light Mapping tends to represent the look of the signal being converted to (i.e. look of target format).

Display-referred (DR) Inverse Tone Mapping (SDR ⇒ HDR)
– Display-referred (DR) preserves displayed colors – use for graded content and graphics.
• Display Referred or DR conversion is the technique that permits pictures displayed in their native display format to
have a similar image appearance when displayed on devices of a different format.
SDR Display
(Gamma on RGB, BT.709)
HLG Display
(Gamma on Y, BT.2020)
Display-referred (DR) Conversion
Images on their respective
displays have similar Look
SDR Source
(BT.709)
HDR Display Light
(HLG BT.2100)
HDRC-4000 HDR Processor
114

Scene-referred (SR) Inverse Tone Mapping for Cameras (SDR ⇒ HDR)
– Scene-referred (SR) preserves the colors of the camera sensor – use for matching the “look” of SDR
cameras with HDR cameras.
• For example, a Scene Referred or SR technique is usually applied when converting the output signal from an SDR
camera to match the color appearance of a native HDR camera output. SR conversion uses an internal “linear light”
processing stage to which the desired output OETF is applied.
Scene Light SDR Camera
CCU
Real-Time Shading
e.g., 1080P @50
(BT.709)
Scene-referred (SR) Conversion
e.g., 1080P @50
HLG (BT.2100)
SDR -> HDR
Display Light
≈
Same
Look
HDR Camera
Scene Light
Real-Time Shading
CCU
e.g., 1080P @50
HLG (BT.2100)
HDR
Display Light
115
HDRC-4000 HDR Processor

– There are two possible approaches to both SDR direct mapping and up-mapping depending on the
application; Display-referred mapping and Scene-referred mapping.
Display-referred Mapping:
– It is used when the goal is to preserve the colours and relative tones seen on an SDR display, when the
content is shown on an HDR display; an example of which is the inclusion of SDR graded content within an
HDR programme.
• Display-referred mappings are derived by scaling the light reproduced by a reference display. These
are known as “display-light” conversions.

– There are two possible approaches to both SDR direct mapping and up-mapping depending on the
application; Display-referred mapping and Scene-referred mapping.
Scene-referred Mapping:
– It is used when the goal is to match the colours and relative tones of an HDR and SDR camera; an example
of which is the inter-mixing of SDR and HDR cameras within a live television production.
• Scene-referred mappings are based on the light falling on the camera sensor, but they include any
camera characteristics, white balance, and any artistic camera adjustments. These are known as
“scene-light” conversions.

Conversion Techniques for SDR <-> HDR
Display-referred (or Display Light) SDR to/from HDR conversion
• Graded content and graphics will appear in the new format as the colorist intended in the original
pictures
• Maintains “look” (i.e. saturation and tone) of content when converted to a new format and ensures that
both the SDR and HDR signals have the same look.
o Should not be used for matching cameras
Scene-referred (or Scene Light) SDR to/from HDR conversion
• Matches the “look” of SDR cameras to HDR cameras
o It should not be used for “graded or archival” SDR content -with HLG (𝒀𝜸) – as it will change the “look”,
and so the artistic intent
118
• Different processes are needed for different applications
• Exercise caution in signal conversions to prevent Side Effects!

Scene-light and Display-light Conversions
119
Scene-light conversion preserves camera sensor colours - use for matching cameras
Display-light conversion preserves displayed colours - use for graded content and graphics

Display-Light SDR to HDR Conversions
120
– Most SDR-HDR format converters attempt to ensure that the displayed “look” of content is preserved as it is
converted from one signal format to another. By doing so, they aim to maintain the “artistic intent” of the
content.
– To achieve that, the conversions first calculate the light produced by the original signal on a reference
display. They then calculate the signal required in the new format, to re-produce the same (or subjectively
similar) display-light on its own reference display. The figure illustrates the conversion for SDR BT.709 to HDR
BT.2100 Hybrid Log-Gamma (HLG), where 𝐿𝑊 is the nominal peak luminance of each simulated display.
To derive the SDR
display-light signals
seen on the mastering
display.
For TV production, the
luminance of the signal
should also be adjusted to
match the signal levels
specified in the ITU-R
BT.2408, to ensure that the
SDR converted signal is
comparable in brightness
to natively produced HDR.
Some “highlight”
expansion may
also be applied
to enhance the
appearance of
the SDR signals,
when intercut
with native HDR

Scene-Light SDR to HDR Conversion
121
– Far better results for color matching cameras can be achieved using scene-light conversions.
– As the conversion process effectively calculates the light falling on the camera sensor, and that is the
same regardless of the production format, it can provide a good color match between SDR and HDR
cameras.
– Some small differences may still be visible in colors that are near or outside of the SDR BT.709 color volume.
But the color volume that is output by the camera can be increased significantly, beyond the strict BT.709
limits, by relaxing the signal clippers on the SDR camera output to EBU R103 levels of +105%, - 5%.
To regenerate the original SDR scenelight signal.
Note that some SDR cameras approximate the
BT.709 OETF with a square-root function, omitting
the linear portion in the ITU-R specification. So
better results in the shadows and black level
tracking can sometimes be achieved by simply
squaring the incoming signal, rather than applying
the exact mathematical inverse of the BT.709 OETF.
A gain adjustment is
applied to ensure that the
SDR nominal peak white
maps to the signal level for
“HDR Reference White”
specified in ITU-R BT.2408,
following the HLG OETF.
An optional “expansion” can be applied to the SDR highlights.
When applying the highlight expansion, through a process
known as “inverse tone-mapping”, it is recommend limiting the
expansion such that the nominal peak SDR signal maps to no
more than 83% of the HLG signal.
Clipping of large areas of an image is common in live SDR
production, so a higher expansion factor would render them too
bright when “up-converted” for HDR display.

Display-Light SDR to HDR Conversions
122
– Whilst such a conversion is precisely what is required for non-live, graded content, it cannot easily be used
for matching SDR and HDR cameras in live production.
– That is because the OOTFs of each production format (BT.709, BT.2020, BT.2100 HLG, BT.2100 PQ,...)are all
different. Even the color primaries may be different.
– So, the displayed colors and tones for objects within a scene will look different for each production format.
– Most formats apply the end-to-end OOTF “gamma” independently on red, green and blue color
components because, in the early days of color television, that was all that was technically possible (HLG is
different).
– By doing so, the displayed colors tend to be more saturated than those in the natural scene.
– The amount of color boost that is introduced depends on the camera exposure and the relative level of
the color components, which in turn depends on the color primaries.

Scene Light vs Display Light Mapping
123
Incoming Signal
In this case, the incoming signal at the
input of the HDR processor, e.g. directly
derived from the output of a camera
operating in PQ-BT2100, corresponds to the
upper green “Signal” block in the figure.
The incoming signal is first used to reconstruct the brightness levels of the scene before the selected mapping operation is performed.
In order to reconstruct the original linear scene light, the non-linear process that took place within the camera during image capture
with PQ-BT2100 must be undone (see the red arrow at top left).
Once the original scene light has been reconstructed,
the actual mapping operation will be performed with
either Direct Mapping (Scene Light) or Tone Mapping
(Scene Light) in order to carry out the HDR-to-SDR
down-conversion (see left green arrow).
The whole process can also be performed in the
reverse arrow direction in case of an up-conversion.
Final SDR signal
“Traditional” BT.709 Look
Since the down-converted scene light is still linear, the non-linear
processing of an SDR camera, according to the OETF specified in
BT.709, has to be simulated in the last step (see blue arrow bottom
left) to get the final SDR signal (bottom green “Signal” block). After
applying the reference BT.709 OETF, the final SDR signal is available
for display on an SDR display.

124
Incoming Signal
In this case, the incoming signal at the input of the HDR
processor, e.g. directly derived from the output of a
camera operating in PQ-BT2100, corresponds to the
upper green “Signal” block in the figure.
By using Display Light Mapping, it is not the brightness values of the scene that are used as a reference for the
mapping, but the brightness levels which the input signal would cause on a reference monitor. In order to
derive the display light, which is caused by this signal on a PQ reference monitor, the EOTF of PQ must be
applied to the signal (see the red arrow at top right), according to the reproduction of such a monitor.
Once the display light has been reconstructed, the
actual mapping operation will be performed with
either Direct Mapping (Scene Light) or Tone Mapping
(Display Light) in order to carry out the HDR-to-SDR
down-conversion (see left green arrow).
Therefore, Display Light Mapping should
be used in order to view HDR content on
displays with a lower dynamic range.
Final SDR signal
PQ Look
Now the down-converted SDR display light must be transferred
into a signal that can be displayed on an SDR monitor using
the BT.1886 EOTF (BT.709 OETF-1 + OOTF). For this purpose,
exactly the inverse of this EOTF must be applied to the signal
(see blue arrow bottom right), i.e. the signal must first be
passed through the inverse BT.709/BT.1886 OOTF (OOTF-1)
before the BT.709 OETF must be applied. Once these steps are
done, the final SDR signal (bottom green “Signal” block) is
available and can be displayed on an SDR monitor.

125
– It is particularly important that Scene Light Mapping is used for matching SDR and HDR camera signals
since both signals represent light from the scene captured by the camera.
− If Display Light Mapping would be used, SDR and HDR cameras (especially HLG camera signals) would not
match, because the displayed look of SDR and HDR images is different due to the difference in the opto-
optical transfer functions (OOTFs).
− Therefore, the difference between scene light and display light is the OOTF.

126
– In this example of HDR-to-SDR down-conversion from PQ-BT2100 to SDR (Gamma BT.709), Display Light
Mapping would, therefore, lead to a PQ look, while Scene Light Mapping would result in a “traditional”
BT.709 look.
• However, in the Scene Light Mapping, the resulting look depends on
 which system the shading takes place (HDR or SDR)
 and whether artistic intents have already been included during capturing process.
Display Light Mapping tends to
preserve the look created by the
transfer characteristic used by the
display (plus artistic intent)
Scene Light Mapping tends to
represent the look of the signal
being converted to.
“Traditional” BT.709 Look PQ Look

127
– In the opposite case of SDR-to-HDR up-conversion from SDR (Gamma BT.709) to PQ-BT2100
• Display Light Mapping would result in the “traditional” BT.709 look (i.e. to preserve the look created by
the transfer characteristic used by the display (plus artistic intent))
• Scene Light Mapping would lead to a PQ look (i.e. look of target format).
Display Light Mapping
tends to preserve the look
created by the transfer
characteristic used by the
display (plus artistic intent)
“Traditional” BT.709 Look
PQ Look
Scene Light Mapping tends
to represent the look of the
signal being converted to.

− Display-referred mappings are derived by scaling the light reproduced by a reference display.
− Maintain the original displayed “look” of content when converted to new format.
− Display-referred mapping is used when the goal is to preserve the colours and relative tones seen on an
SDR BT.709 or BT.2020 display, when the content is shown on a BT.2100 HDR display; possibly at a slightly
higher peak luminance to provide a value for diffuse white and skin tones that is more consistent with the
brightness of native HDR content (direct mapping).
• An example of which is the inclusion of SDR graded content within an HDR programme.
128
Display-referred (Display-light) Conversion, Summary
SDR Content
(BT.709 or BT.2020)
Maintain the original displayed
“look” of content when
converted to new format.
HDR Content
(BT.709 or BT.2020)
Convert HDR BT.2020
SDR Content
(BT.709 or BT.2020)
HDR Content
(BT.709 or BT.2020)
Convert SDR Content
(BT.709 or BT.2020)

− Each production format looks different due to different OOTFs )Hue, Saturation and Tone). Display-referred
mapping maintain the original displayed “look” of content when converted to new format.
– Display Light Mapping should be used in order to view HDR content on displays with a lower dynamic
range.
− Display-referred mapping is adopted so that the converted SDR content looks similar (except in dynamic
range) to the original HDR content (up mapping).
− Where the broadcaster’s SDR services is considered the main output (SDR TX output), it should be via a
display-light converter (down mapping).
129
SDR Content
(BT.709 or BT.2020)
HDR Content
(BT.709 or BT.2020)
Convert HDR BT.2020
SDR Content
(BT.709 or BT.2020)
HDR Content
(BT.709 or BT.2020)
Convert SDR Content
(BT.709 or BT.2020)

− The brightness levels which the input signal would cause on a reference monitor are used as a reference
for the mapping.
− A display-light conversion ensures that both the SDR and HDR signals have the same look (down
mapping).
− It should be used to preserve the appearance of the HDR signal when converting to SDR (down mapping).
− A display-light conversion ensures that both the SDR and HDR signals have the same look (down
mapping).
− In PQ based production, the difference between display-light and scene-light conversion of BT.2020
signals is relatively minor and current practice is to use display-light conversion.
130
SDR Content
(BT.709 or BT.2020)
HDR Content
(BT.709 or BT.2020)
Convert HDR BT.2020
SDR Content
(BT.709 or BT.2020)
HDR Content
(BT.709 or BT.2020)
Convert SDR Content
(BT.709 or BT.2020)

− For any SDR output containing graphics (e.g. for the broadcaster’s own SDR service) a display-light
conversion is recommended, as that should ensure the same hue and saturation of graphics in both HDR
and SDR outputs.
− For SDR Graphics, commercials, legacy material (graded, archival), ITU-R BT.709 broadcast feeds, server-
based content (Super Slow-Motion effects) to be converted into HDR using a Display Referred conversion
technique, in order to preserve its original “look” and the artistic intent (up mapping).
− The graded content should be inserted into the HDR programme using display-light direct mapping or up-
mapping, to preserve its original “look” and the artistic intent; SDR graphics should be directly mapped
into the HDR format.
− Where the desire is to maintain the colour branding of the SDR graphics, a display-light mapping should
be used (direct mapping).
− Display Light Mapping should be used in order to view HDR content on displays with a lower dynamic
range.
131

SDR content over HDR Transmission
a）SDR on HDR broadcasting channels
b） HLG signals from SDR original content
• New UHD broadcasting services employ Playout Servers with a mixture of SDR and HDR programs or SDR
commercials inserted on main HDR programs. Sometimes it is required to maintain the look of the SDR
program due to content owner preference.
• A solution is to use a “Display-referred” processing technique to avoid switching the EOTF from HDR in the
consumer TV set while maintaining the picture look established for the SDR signal.
HDR transmission
channel
SDR Range SDR Range
SDR on HDR
HDR SDR on HDR
HDR HDR
Switching of Display
EOTF curves
Switching times depend on TV
implementation
132

− Scene-referred mappings are based on the light falling on the camera sensor, but they include any
camera characteristics, white balance, and any artistic camera adjustments.
− It is used where the source is a direct SDR camera output and the goal is to match the colors and lowlights
and mid-tones (relative tones) of this camera with signal from a BT.2100 HDR camera; an example of which
is the inter-mixing of SDR and HDR cameras within a live television production.
− SDR, HDR Cameras should be matched in tone and color appearance using a scene-referred (scene light)
conversion process.
133
Scene-referred (Scene-light) Conversion, Summary
SDR camera output
(BT.709 or BT.2020)
To match the colors and
lowlights and mid-tones
(relative tones)
HDR camera output
(BT.709 or BT.2020)
Convert HDR BT.2020 SDR camera output
(BT.709 or BT.2020)
To match the colors and
lowlights and mid-tones
(relative tones)
HDR camera output
(BT.709 or BT.2020) Convert SDR Content
(BT.709 or BT.2020)

− Where the “clean or World Feed” is considered the main output, it may be via a scene-light converter
(down mapping). The “clean or World Feed” SDR signal may be derived from the HDR signal using a
scene-light conversion, to match other broadcasters’ SDR cameras that may also be present at the venue
(down mapping).
− Where the desire is to match signage within the captured scene (in-vision signage; e.g. a score board at a
sporting event), a scene-light mapping is usually preferred(direct mapping).
− A scene-light HDR to SDR conversion may also be used where it is important to colour match the converted
PQ or HLG output to downstream SDR BT.709 cameras.
− In HDR focused production scene light tone mapping should be used to ensure maximum compatibility
with conventional SDR productions. HDR cameras should be converted to SDR BT.709 using a scene-light
conversion to match the native SDR cameras. 134

Scene-referred or Display-referred conversion for SDR to HLG HDR
− It is particularly important that the scene-referred mapping is used for matching signals from BT.709 and
BT.2020 SDR cameras with signals from HLG cameras. This is because, direct from the camera (and prior to
subjective adjustment), both signals represent light from the scene captured by the camera.
− If the display-referred mapping were used, which maintains the appearance of SDR images on an HLG
display, the signals from SDR cameras and HLG cameras would not match. This is because the displayed
‘look’ of SDR and HLG images, from cameras that implement the reference OETFs, is different.
Scene-referred or Display-referred conversion for SDR to PQ HDR
− Scene-referred mapping will also work for mapping SDR to PQ.
− However, because the ‘look’ of PQ and BT.2020 SDR signals is very similar, for BT.2020 SDR signals the
display-referred mapping will generally work well.
− To best match the PQ ‘look’, BT.709 SDR camera signals could be converted to BT.2020 SDR camera signals
before display-referred mapping is applied.
135

Scene or Display Referred Conversion?
− Widespread confusion between industries and short hand nomenclature
• Mapping via Scene or Display light
• A Scene or a Display Referred system
• ACES definitions of a Scene or Display Referred input and output Images
136
Graphics or Test Patterns, SDR or HDR Display light
SDR to HDR Adverts Display light
HDR to SDR Program Display light
HDR to HDR Program Display light
Sony S-Log3 to SDR to match camera native SDR Scene light
To or from SDR BT.709 Cameras looking at the same Scene light
Conversion Content/intention Conversion Type : Via

Display-referred (or Display Light) SDR to/from HDR conversion
• Graded content and graphics will appear in the new format as the colorist intended in the original
pictures
• Maintains “look” (i.e. saturation and tone) of content when converted to a new format and ensures that
both the SDR and HDR signals have the same look.
o Should not be used for matching cameras
Scene-referred (or Scene Light) SDR to/from HDR conversion
• Matches the “look” of SDR cameras to HDR cameras
o It should not be used for “graded or archival” SDR content -with HLG (𝒀𝜸) – as it will change the “look”,
and so the artistic intent
137
• Different processes are needed for different applications
• Exercise caution in signal conversions to prevent Side Effects!
Scene or Display Referred Conversion?

Scene-referred (or Scene Light) SDR BT.709 to PQ LUT Conversion
− SDR and HDR displays DO NOT match.
− Blacks are stretched in the BT1886 Display but not the PQ Display (matches scene)
2084 HDR (PQ) 0% 2 % 18% 90% 100%
BT.709 100nits 0 9 41 95 100
HDR 1000nits 0 37 58 75 76
HDR 2000nits 0 31 51 68 68
HDR 5000nit 0 24 42 58 59
Camera-Side Conversion
BT.709 to PQ
Camera-Side Conversion
BT.709 (SDR) to PQ1K, PQ2K, PQ5K
BT.709 % IRE
PQ
Signal
Level
(%)
BT.709 to PQ1K
BT.709 to PQ2K
BT.709 to PQ5K
138
9 41 95 100

Display-referred (or Display Light) 709 to PQ LUT Conversion
− SDR and HDR displays match
− Blacks are stretched in both the BT1886 and PQ Display
Display-Side Conversion
BT.709 to PQ
BT.709 % IRE
2084 HDR (PQ) 0% 2 % 18% 90% 100%
BT.709 100nits 0 9 41 90 100
HDR 1000nits 0 22 52 74 75
HDR 2000nits 0 17 46 66 68
HDR 5000nit 0 13 37 57 58
Display-Side Conversion
BT.709 (SDR) to PQ1K, PQ2K, PQ5K
BT.709 to PQ1K
BT.709 to PQ2K
BT.709 to PQ5K
139
9 41 90 100
PQ
Signal
Level
(%)

How Bright is White in HDR-TV?
− Static format converters rely on signal levels
defined in ITU-R report BT.2408
• With help from the EBU PTS
− HDR Reference White = 58% PQ or 75% HLG
Reflectance Object or Reference
(Luminance Factor, %)
Nominal Luminance
Value (PQ & HLG)
[Display Peak
Luminance, 1000 nit]
Nominal
Signal
Level (%)
PQ
Nominal
Signal
Level (%)
HLG
Grey Card (18% Reflectance) 26 nit 38 38
Greyscale Chart Max (83%
Reflectance)
162 nit 56 71
Greyscale Chart Max (90%
Reflectance)
179 nit 57 73
Reference Level:
HDR Reference White (100%
Reflectance) also Diffuse White and
Graphics White
203 nit 58 75
Preliminary signal levels for common objects in PQ and HLG production
Reflectance object
Nominal Luminance, cd/m²
(for a PQ reference display, or a
1 000 cd/m² HLG display)
Signal level
%PQ %HLG
Skin Tones (Fitzpatrick Scale)
Type 1-2 Light skin tone 65-110 45-55 55-65
Type 3-4 Medium skin tone 40-85 40-50 45-60
Type 5-6 Dark skin tone4 10-40 30-40 25-45
Grass 30-65 40-45 40-55
Nominal signal levels for shading [Display Peak Luminance, 1000 nit]
140

Assessing Colours of Different Production Formats
− The amount by which colors vary between scene and display light can be predicted using published
data for a “Macbeth” ColorChecker test chart and a simple mathematical model, shown in the figure.
− Compare results using 𝑰𝑪𝑻𝑪𝑷
• Said to be perceptually uniform and work well for HDR
X-Rite ColorCheckerdata CIEL*a*b*
141
The CIE L*a*b* data is converted to XYZ scene-light, and from there to 𝑹𝒔, 𝑮𝒔, 𝑩𝒔 signals in either BT.709 or BT.2020 color. The
scene-light signals are then linearly scaled (similar to the effect of a camera iris) to achieve the desired signal level
following the camera OETF. The non-linear signals are then passed through each system’s reference EOTF and converted to
𝑰𝑪𝑻𝑪𝑷 (PQ) for comparison. We have chosen to compare colors using a 𝑪𝑻𝑪𝑷 chart rather than the more usual CIE u'v' or xy
chromaticity charts, as the 𝑰𝑪𝑻𝑪𝑷 representation is more perceptually uniform and can also be applied to HDR signals.
Approximately 10 JNDs
(J. Pytlarz, E. Pieri, “Hitting the Mark— A
New Color Difference Metric for HDR
and WCG Imagery”, SMPTE Mot. Imag.
J., 127 (3): 18-25, April 2018.)

Results of 𝐈𝐂𝐓𝐂𝐏 Analysis
142
− The scene-light colors are marked with blue
circles, and the colors co-ordinates with
red triangles.
− The displayed light 𝑪𝑻𝑪𝑷 co-ordinates of
the 18 color patches of the “Macbeth”
chart for HLG are coincident with the
actual colors in the scene.
− BT.2100 HLG scene and displayed colours
are identical so only the scene colors are
shown.
− The 𝑪𝑻𝑪𝑷 coordinates for “dark skin” and
“light skin” are almost identical, as these
two colors are distinguished by their
Intensity component, I, which is not shown
in the plots.

BT.709 – Some Displayed Colors Close to Scene Others Very Different
143
− The cyan and blue colors are actually
outside of the BT.709 color gamut, which
this simple analysis ignores.
− So distortions for those two colors in BT.709
will likely be greater in practice.
− The hue and saturation differences can
clearly be seen to vary according to
color and TV format.
− As an example, in BT.709 the displayed
“red” color patch is shifted in both hue
and saturation, yet the “bluish green” is
remarkably true to life.

“Traditional Colour” Variant of HLG
144
− The differences in BT.2020 are even
greater, particularly in the blues, yellows
and reds.

PQ Displayed Colours Even More Saturated than BT.709
145
− BT.2020 and PQ are similar, as they share
the same color primaries and OOTF, but
slightly greater in PQ as the signal levels
differ.

PQ Displayed Colours Even More Saturated than BT.709
146
− BT.2020 and PQ are similar, as they share
the same color primaries and OOTF, but
slightly greater in PQ as the signal levels
differ.
Note:
− One reference suggests that a difference of
1/360 CT, or 1/720 CP is a just noticeable
difference (JND). So, many of the color shifts
between the scene and displayed light will be
clearly visible – approximately 20 JNDs for
“moderate red” in BT.709 and even greater in
BT.2020 and PQ.
− So, the same scene shot by BT.709, BT.2020,
BT.2100 PQ and BT.2100 HLG cameras will look
quite different on their respective reference
displays.

Macbeth Chart and Greyscale Chart Shot in a Studio
147
− BT.2100 HLG and BT.709 outputs from a Sony HDC-4300 camera (The images have been converted for
display on an sRGB computer monitor).
BT.2100 HLG SDR BT.709 with display-light conversion to HLG

Macbeth Chart and Greyscale Chart Shot in a Studio
148
− The HLG colors in are close to those in the original scene, whilst those in right figure are closer to those seen
on a BT.709 reference display. As predicted by the theoretical analysis, a large difference can be seen in
both the hue and saturation of the red color patch in the two figures.
− Smaller saturation differences are seen for other colors, and very little difference can be seen for bluish
green (top right) and foliage color patches (middle top).
− So intercutting HDR and converted SDR cameras is likely to be unsatisfactory with display-light conversion.
BT.2100 HLG SDR BT.709 with display-light conversion to HLG

– The simplest type of mapping is the Direct Mapping since changes in luminance are only made
proportionally with a slight gain. This gain is applied in order to keep the appearance between SDR and
HDR white levels about the same.
– In the context of converting SDR content to HDR content, Direct Mapping preserves the appearance of the
SDR content so that the HDR version displayed on a reference HDR monitor will look identical to the original
SDR version displayed on a reference SDR monitor.
– This approach is intended to preserve the ‘look’ of the SDR content when shown on an HDR display.
Direct Mapping (Mapping)
150
SDR Content
(BT.709 or BT.2020)
Preserved SDR Look
(Without Expanded
Luminance Range) HDR BT.2020 Display
HDR Signal

– Direct-mapping refers to the process of simply placing SDR content into an HDR signal container, at the
correct signal level.
• Typically 100% SDR > “HDR Reference White”, 75% HLG signal
– Direct mapping places SDR content into an HDR container, analogously to how content specified using
BT.709 colorimetry may be placed in a BT.2020 container.
– A luminance gain (e.g. 2x) and other processing will provide a better match to the luminance of a native
HDR image while maintaining the SDR appearance.
151
SDR Content
(BT.709 or BT.2020)
Preserved SDR Look
(Without Expanded
Luminance Range) HDR BT.2020 Display
HDR Signal

– Direct Mapping is also “useful when the signal from an HDR camera is required to look similar to the signal
delivered by an SDR camera operated without a ‘knee’”, which is sometimes used in conventional video
cameras in order to exploit their full dynamic range and thus to extend the dynamic range of the signal.
– However, in this case of down-conversion, this also means that (high-)lights above the SDR format are
simply cut off, which leads to severe clipping of highlights in the down-converted SDR image.
– As a result, the picture will be burnt out in bright areas. Thus, the converted SDR does not benefit from the
increased capture quality of HDR due to the high loss in lights and shadows.
– Therefore, this procedure is only suitable for scenes with a lower contrast range in this case of down-
conversion or to match HDR cameras with SDR cameras.
– However, this approach is well predictable and leads to a steep image impression.
152

Display-referred Mapping
To preserve the colors and relative tones of an SDR content on HDR Display
HDR Signal
SDR Content
(BT.709 or BT.2020)
(Without Expanded
Luminance Range)
Preserved SDR Look
HDR BT.2020 Display
Display-referred Direct Mapping and Scene-referred Direct Mapping
153
– Display-referred mapping is used when the goal is to preserve the colours and relative tones seen on an
SDR BT.709 or BT.2020 display, when the content is shown on a BT.2100 HDR display.
– The brightness levels which the input signal would cause on a reference monitor are used as a reference
for the mapping. An example of which is the inclusion of SDR graded content within an HDR programme.
– Each production format looks different due to different OOTFs (Hue, Saturation and Tone). Display-referred
mapping maintain the original displayed “look” of content when converted to new format.
Real HDR Signal

Real HDR Signal
154
– Scene-referred mapping is used where the source is a direct SDR camera output and the goal is to match
the colours and tones of a BT.2100 HDR camera.
– An example of which is the inter-mixing of SDR and HDR cameras within a live television production.
– “Scene-light” conversions based on the light falling on the camera sensor. Always the same regardless of
production format, so they are used for matching cameras.
SDR camera output
(BT.709 or BT.2020)
HDR Signal
Preserved SDR Look
in HDR Program (Ex: 20%)
(Without Expanded
Luminance Range)
HDR BT.2020 Display
Scene-referred Mapping
To match the colors and lowlights and mid-tones of an SDR camera with HDR camera

To preserve the colors and relative tones of an SDR content on HDR Display
HDR Signal
SDR Content
(BT.709 or BT.2020)
(Without Expanded
Luminance Range)
Preserved SDR Look
HDR BT.2020 Display
155
SDR camera output
(BT.709 or BT.2020)
HDR Signal
Preserved SDR Look
in HDR Program (Ex: 20%)
(Without Expanded
Luminance Range)
HDR BT.2020 Display
To match the colors and lowlights and mid-tones of an SDR camera with HDR camera
Real HDR Signal

Example: Mapping of SDR Graphics
− SDR graphics should be directly mapped into the HDR signal at the “Graphics White” signal level specified
in (75% HLG or 58% PQ) to avoid them appearing too bright, and thus making the underlying video appear
dull in comparison.
156
• Where the desire is to maintain the colour branding of the SDR
graphics, a display-light mapping should be used.
• Where the desire is to match signage within the captured scene
(in-vision signage; e.g. a score board at a sporting event), a
scene-light mapping is usually preferred.
− Work is currently underway to determine the best practice for HDR
key signals.
− In the interim, using an SDR key signal directly has been found to
deliver satisfactory results.

157
− LYNXTechnik AG, Broadcast Television Equipment.
The Green Machine HDR STATIC Constellation
LYNXTechnik AG

158
− This table gives information on which luminance
100% ‘SDR reference white’ will be mapped onto an
HDR reference monitor with 1000 cd/m² in case of up-
conversion (see the left side in blue) and which
luminance displayed on an HDR reference monitor
with 1000 cd/m² will be mapped to 100% ‘SDR
reference white’ in case of down-conversion (see the
right side in green).
− As shown in the table, these values are fairly
accurate to the HDR level guidance provided in ITU
Report BT.2408 (203 cd/m² reference level). Thus, it is
ensured that SDR and HDR content has a similar level
for HDR reference white.
− The table contains the scene luminance (i.e. with
inverted OOTF) corresponding to the respective
display luminance already mentioned.
The Direct Mapping Operation of the green Machine HDR STATIC Constellation
* luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² (table
without clipping)
** luminance [in cd/m²] in the scene (inverting the OOTF)
*** luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² which will
be mapped to 100% SDR reference white
**** luminance [in cd/m²] in the scene (inverting the OOTF) which will be mapped
to 100% SDR reference white
LYNXTechnik AG

− To adjust the luminance of the overall image. Basically, it changes the slope or lift of the luminance level.
− A value less than 0 dB reduces the brightness and a value greater than 0 dB increases the brightness.
• +12,00 dB: extremely increased brightness
• +0.00 dB: unchanged
• -12,00 dB: extremely decreased brightness
Gain [dB] Parameter Role in HDR Conversion
An increased gain can
lead to clipping of the
lights for high luminance
values at the input.
− If the image appears too dark, e.g. after an SDR-to-HDR up-
conversion, a luminance gain can be used to adjust the
image and achieve better matching to the luminance of
native HDR material.
− This processing can be undone in case of “round-tripping”
if the inverse value is used for the reverse conversion.
• For example, if the value +3.0 dB was selected during the first
conversion from SDR to HDR, the value -3.0 dB must be
selected during reconversion back from HDR to SDR.
159

160
Direct Mapping Operation Example
* luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² (table
without clipping)
** luminance [in cd/m²] in the scene (inverting the OOTF)
*** luminance [in cd/m²] on an HDR reference monitor with 1000 cd/m² which will
be mapped to 100% SDR reference white
**** luminance [in cd/m²] in the scene (inverting the OOTF) which will be mapped
to 100% SDR reference white
LYNXTechnik AG
− In the case of “round-tripping” an SDR signal
(SDR>HDR>SDR) using the Mapping Type “Direct
Mapping Display Light”, a gain of +6.0 dB is used
during up-conversion, since the HDR result without
adjusting the gain would appear too dark compared
to native HDR content. In this case, the 100% ‘SDR
reference white’ of this signal will be mapped to be
displayed with 398 cd/m² on an HDR reference
monitor with 1000 cd/m² peak luminance.
− The scene luminance corresponding to this display
luminance is 557 cd/m². When down-converting this
signal back to SDR, the gain parameter must be set
to -6.0 dB in order to map back the exact value of
398 cd/m² displayed on the HDR reference monitor
with 1000 cd/m² peak luminance to the level of the
initial 100% ‘SDR reference white’.

− The brightness adjustment affects the color impression such as the saturation.
− Due to these changes, the chrominance is generally treated accordingly. If the saturation impression still
does not match the expectations, the "Saturation" parameter offers the possibility to adjust it.
• 2.0: extremely increased saturation
• 1.0: saturation unchanged
• 0.0: extremely reduced saturation
Saturation Parameter Role in HDR Conversion
An increase in saturation
can lead to color
clipping for already
highly saturated colors
at the input.
− This processing can be undone in case of “round-tripping”
if the inverse value is used for the reverse conversion.
• For example, if the value 1.2 was selected during the
first conversion from SDR to HDR, the value 1/1.2 ≈ 0.83
must be selected during reconversion back from HDR
to SDR.
161

− The following table shows which settings of the individual processing parameters are considered
meaningful and which are critical.
− The default value is marked with a cross. Extreme areas that carry an increased risk of undesired behavior
are marked in red.
Saturation Parameter Role in HDR Conversion
An increase in saturation
can lead to color
clipping for already
highly saturated colors
at the input.
162

𝑬 = 𝑬′ 𝟐.𝟒𝟎
, 𝟎 ≤ 𝑬′ ≤ 𝟏
𝑬′
Scaling: To ensure that SDR and native HDR content have a similar level for HDR reference white. (58 % PQ or 75 % HLG respectively)
𝑬′
𝑬
𝑬
Mapping of SDR Content into HDR
(Linear)
E
𝐸′
𝐸′
E
𝐸=(𝐸′)𝟐
An approximation of EOTF ITU R BT.1886
E′ is the non-linear signal (R′, G′, B′) in the range [0:1]
E is the normalized linear display light in the range [0:1]
Optional OOTF Adjustment: To compensate for the subjective change in appearance of the SDR signal arising from a simple linear scaling; thereby
ensuring that the visibility of detail in the shadows is maintained and that the level of skin tones in HDR and mapped SDR content are similar.
The non-linear video signal is converted to linear
“scene light” by applying the approximate
inverse of SDR OETF, 𝐸=(𝐸′)𝟐
163
(Linear)

Display-referred Mapping of SDR into HDR
Optional OOTF Adjustment: To compensate for the subjective change in appearance of the SDR signal
arising from a simple linear scaling; thereby ensuring that the visibility of detail in the shadows is
maintained and that the level of skin tones in HDR and mapped SDR content are similar.
𝑬′
𝑬′
𝑬
𝑬
𝑬 = 𝑬′ 𝟐.𝟒𝟎
, 𝟎 ≤ 𝑬′ ≤ 𝟏
Scaling: To ensure that SDR and native HDR content have a similar
level for HDR reference white. (58 % PQ or 75 % HLG respectively)
164
(Linear)

Display-referred Mapping of SDR into PQ
− The following procedure may be followed to achieve consistent mid-tone luminance levels when
mapping SDR content into PQ.
𝑬′ = 𝑬𝑶𝑻𝑭𝑷𝑸
−𝟏
[𝒔𝒄𝒂𝒍𝒊𝒏𝒈 × 𝑬𝑶𝑻𝑭𝟏𝟖𝟖𝟔[𝑽, 𝑳𝑾, 𝑳𝑩]]
𝐸′: Output PQ video signal level (normalized [0:1]) 𝑉: Input SDR video signal level (normalized, black at V = 0, to white at V = 1)
𝑳𝑾: SDR screen luminance for white = 100 cd/m² 𝑳𝑩: Screen luminance for black = 0 cd/m²
Scaling: EOTFPQ (𝐸𝑉=1
′
) / 100 cd/m²
Example: for scaling = 2.0, E′V=1 = 0.58 (0.58% PQ) and EOTFPQ (E′V=1) = 200 cd/m²
165
PQ
PQ
PQ
𝑬
𝑬′
𝑬′
𝑬
Scaling: To ensure that SDR and native HDR content have a
similar level for HDR reference white. (58 % PQ)
𝑬 = 𝑬′ 𝟐.𝟒𝟎 , 𝟎 ≤ 𝑬′ ≤ 𝟏
(Linear)
PQ/2020
Video

• Unity mapping: it does not change the display of the SDR content (it will display on the PQ HDR
reference monitor the same as it displayed on the reference SDR monitor).
⇒ Thus, no OOTF adjustment of the SDR display light signal is necessary.
• For unity mapping the peak signal of SDR content should be set to 100 cd/m² or 51% PQ.
PQ
PQ
PQ
𝑬
𝑬′
𝑬′
𝑬
𝑬 = 𝑬′ 𝟐.𝟒𝟎 , 𝟎 ≤ 𝑬′ ≤ 𝟏
166
(Linear)
PQ/2020
Video

• If the SDR content is being inserted into HDR programming, and there is desire to more closely match
the brightness of the HDR content, and that brightness is known, scaling can be done to bring up the
brightness of the mapped SDR content.
• Scaling should be performed with care lest scaled SDR content, in particular skin tones, becomes
brighter than in the HDR content.
PQ
PQ
PQ
𝑬
𝑬′
𝑬′
𝑬
𝑬 = 𝑬′ 𝟐.𝟒𝟎 , 𝟎 ≤ 𝑬′ ≤ 𝟏
167
(Linear)
PQ/2020
Video

Display-referred Mapping of SDR into HLG
Mapping without Gamma Adjustment
𝑬 = 𝑬′ 𝟐.𝟒𝟎
, 𝟎 ≤ 𝑬′ ≤ 𝟏
The linear SDR display light is scaled to ensure
that 100% of the SDR signal is mapped to the
HLG reference level 75 %HLG.
168
(Linear)

A small gamma adjustment may then optionally be applied
to the luminance component, to compensate for the
subjective change in appearance of the SDR signal arising
from a simple linear scaling of the SDR display light signal.
Mapping with Gamma Adjustment
𝑬 = 𝑬′ 𝟐.𝟒𝟎
, 𝟎 ≤ 𝑬′ ≤ 𝟏
The linear SDR display light is scaled to ensure
that 100% of the SDR signal is mapped to the
HLG reference level 75 %HLG.
169
(Linear)

Scaling
− When (100X)% SDR signal is mapped to (100Y)% HLG signal, a scaling gain is calculated by the following
equation:
− For example, when 100% SDR signal is mapped to 75% HLG (203 cd/m² on a 1000 cd/m² display), the
scaling gain is calculated as follows:
170
 
 
 
 
 
203
.
0
0
.
1
265
.
0
0
.
1
EOTF
75
.
0
OETF
OOTF
0
.
1
EOTF
75
.
0
EOTF
Gain 4
.
2
2
.
1
SDR
-1
HLG
HLG
SDR
HLG





Simplification of the HLG mapping process
− Through careful choice of the HLG inverse EOTF parameters, it is possible to avoid the need to scale and
adjust the gamma of the SDR linear display light signal.
− By configuring the HLG inverse EOTF with a nominal peak luminance, 𝐿𝑊, of 392 cd/m², an input of 100
cd/m² from the SDR EOTF will directly deliver an HLG signal of 75%, satisfying the requirement to map
100% SDR signal to 75% HLG signal, without further scaling and gamma adjustment.
− Figure illustrates how, for all but the most critical applications, it is possible to simplify the conversion yet
further.
171

Simplification of the HLG mapping process
− When applying the HLG inverse EOTF with 𝐿𝑊 set to 392 cd/m², Note 5e of BT.2100 requires a gamma
value of 1.03.
− As this is close to unity, in most applications there is no need to apply the inverse OOTF gamma to the
luminance component, it can instead be applied independently to R, G and B components; greatly
simplifying the mapping process.
− Colour distortions that usually arise through applying gamma to red, green and blue, rather than
luminance, are barely visible for such low values of gamma.
− As normalised signals are used throughout, a different scaling is required to match the signal ranges of
the SDR EOTF and HDR inverse EOTF, thereby ensuring that 100% SDR signal maps to 75% of the HLG HDR
signal.
− Note that as the normalised signals are dimensionless, the scaler is not adjusting the peak luminance of
the SDR display light, so no additional gamma compensation for the signal scaling is required. Allowing
for the inverse OOTF gamma of 1.03, the correct scale factor is 0.2546.
172

Scene-referred Mapping of SDR into HDR (HLG and PQ)
E
𝐸′
𝐸′
E
𝐸=(𝐸′)𝟐
To compensate for any subjective
adjustments made to the HDR and SDR
camera reference OETFs
The non-linear video signal is converted to
linear “scene light” by applying the
approximate inverse of SDR OETF, 𝐸=(𝐸′)𝟐
The scene light signal is then scaled so that after applying
the reference PQ or HLG OETF, the non-linear signal is at
the appropriate signal level for HDR reference white (58
%PQ or 75 %HLG respectively).
173
(Linear)
− The schematic diagram of the scene-referred mapping for both PQ and HLG.

Scene-referred Mapping of SDR into HLG
Where the SDR “look” is maintained during the conversion from SDR to HDR or the HLG
camera is designed to deliver a traditional “look”, a small optional adjustment to the
OOTF may then be applied to compensate for the subjective change in appearance of
the SDR signal arising from a difference between HLG and SDR OOTFs.
𝐸=(𝐸′)𝟐
 
 
265
.
0
0
.
1
265
.
0
0
.
1
OETF
75
.
0
OETF
Gain 0
.
2
1
-
SDR
-1
HLG



The non-linear video signal is converted to
linear “scene light” by applying the
approximate inverse of SDR OETF, 𝐸=(𝐸′)𝟐
SDR to HLG Mapping with Gamma Adjustment (Scene-Referred)
174
(Linear)
For example, when 100% SDR signal is mapped to 75%
HLG signal, the scaling gain is calculated as follows:

175
Conversion Practices for Camera and Display RGB Colorimetry
− Several camera and display systems, for both professional and consumer applications, use their own
colour primaries, a practice that may give them certain advantages during capture or display
respectively.
− However, content captured or displayed on such devices would still have to be transformed to or from a
Recommendation ITU-R BT.2100 workflow, respectively.
− It should be noted that the transformations in this document only apply under the following conditions:
• The source and target white points are the same and should be equal to D65.
• The source and target white point brightness is the same. For scenarios where brightness is different,
refer to Report ITU-R BT.2446.
− Furthermore, these transformations are not applicable for camera raw signals.

176
Conversion Practices for Camera and Display RGB Colorimetry
− Camera and display systems are commonly defined by their normalized primary matrix, NPM where the
elements of the matrix depend on the chromaticity coordinates, (xR, yR), (xG, yG), (xB, yB), and (xW, yW) for
red, green, blue, and white, respectively, that characterize each system.
− First, compute the z coordinates for all colour primaries and then the matrix elements of NPM are derived
as follows:
zR = 1 – (xR + yR)
zG = 1 – (xG + yG)
zB = 1 – (xB + yB)
zW = 1 – (xW + yW)
XR =
yG∗zB−yB∗zG ∗xW+ xB∗zG−xG∗zB ∗yW+ xG∗yB−xB∗yG ∗zW ∗xR
xR∗ yG∗zB−yB∗zG −xG∗ yR∗zB−yB∗zR +xB∗ yR∗zG−yG∗zR ∗yW
XG =
yB∗zR−yR∗zB ∗xW+ xR∗zB−xB∗zR ∗yW+ xB∗yR−xR∗yB ∗zW ∗xG
XB =
yR∗zG−yG∗zR ∗xW+ xG∗zR−xR∗zG ∗yW+ xR∗yG−xG∗yR ∗zW ∗xB
YR =
yG∗zB−yB∗zG ∗xW+ xB∗zG−xG∗zB ∗yW+ xG∗yB−xB∗yG ∗zW ∗yR
YG =
yB∗zR−yR∗zB ∗xW+ xR∗zB−xB∗zR ∗yW+ xB∗yR−xR∗yB ∗zW ∗yG
YB =
yR∗zG−yG∗zR ∗xW+ xG∗zR−xR∗zG ∗yW+ xR∗yG−xG∗yR ∗zW ∗yB
ZR =
yG∗zB−yB∗zG ∗xW+ xB∗zG−xG∗zB ∗yW+ xG∗yB−xB∗yG ∗zW ∗zR
ZG =
yB∗zR−yR∗zB ∗xW+ xR∗zB−xB∗zR ∗yW+ xB∗yR−xR∗yB ∗zW ∗zG
ZB =
yR∗zG−yG∗zR ∗xW+ xG∗zR−xR∗zG ∗yW+ xR∗yG−xG∗yR ∗zW ∗zB
𝐍𝐏𝐌 =
𝐗𝐑 𝐗𝐆 𝐗𝐁
𝐘𝐑 𝐘𝐆 𝐘𝐁
𝐙𝐑 𝐙𝐆 𝐙𝐁

177
Conversion of arbitrary display referred linear light signals to BT.2100 signals using a display referred workflow
Conversion of Normalized Linear Colour Signals to ITU-R BT.2100
− The conversion process, assuming a display referred camera workflow, as well as the final conversion to a
BT.2100 representation. For conversion to HLG, a bridge point of 1000 cd/m² is assumed, and can therefore
use the reference OOTF.
• The NPM is needed for the conversion process to and from the CIE XYZ colour space and the BT.2100
colour space.

178
Conversion of arbitrary display referred linear light signals to BT.2100 signals using a display referred workflow
− The negative values may be clipped to zero.
− The positive values may also be clipped to the capabilities of the interface.
− Although both soft or hard clipping could be performed in many applications hard clipping is preferred.
− In the scenario that hard clipping of only the negative values is performed the process would be as follows:
ER = Max(0, ER)
EG = Max(0, EG)
EB = Max(0, EB)

179
Conversion of arbitrary scene referred light signals to a BT.2100 HLG signal using a scene referred workflow
− The figure depicts the conversion process when applied on a scene referred workflow with the HLG
Recommendation ITU-R BT.2100 signal as its output.

180
Conversion of arbitrary scene referred light signals to a BT.2100 PQ signal using a scene referred workflow
− The figure depicts the same conversion process when applied on a scene referred workflow with the PQ
Recommendation ITU-R BT.2100 signal as its output.

181
Conversion of Recommendation ITU-R BT.2100 signals to an arbitrary display using a display referred workflow
− The figure depicts conversion process assuming a display referred workflow for both PQ and HLG.
− For conversion from HLG, the nominal peak luminance of the target display (and the appropriate system
gamma) is used for the HLG OOTF.
• The negative values may be clipped to zero.
The positive values may also be clipped to
the capabilities of the display.
• Although both soft or hard clipping could be
performed, in many applications, such as
when using a reference display, hard clipping
is preferred.
• In the scenario that hard clipping of only the
negative values is performed the process
would be as follows:
ER = Max(0, ER)
EG = Max(0, EG)
EB = Max(0, EB)
Conversion of BT.2100 to Arbitrary Linear Colour Signals for Display Systems

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