Digital Theory 1.pdf

DIGITAL THEORY 1
COLOUR MANAGEMENT - FROM
CAMERA TO PRINT
• RAW FILES & DYNAMIC RANGE
• WHITE BALANCE & COLOUR TEMPERATURE
• CALIBRATION & PROFILING
• RGB v CMYK

DIGITAL CAPTURE -
FROM CAMERA TO SCANNER
• DIGI-CAMERA FILES – RAW & DYNAMIC RANGE
• COLOUR TEMPERATURE/WHITE BALANCE
• COLOUR SPACE
• GAMUT
• SHORT ACTIVITY AROUND PRACTICAL
ASPECTS FOR PUBLICATION.
• QUICKFIRE TUTORIALS FOR WEEK 11 SESSION

• The
light
sensi,ve
cells
are
overlaid
with

a
mosaic
of
red,
green
or
blue
ﬁlters.

• This
tri-‐colour
arrangement
is
very

similar
to
the
addi$ve
colour
system
of

early
forms
of
colour
photography
such

as
Autochromes.

• There
are
more
green
ﬁlters
to
bias
the

light
responses
closer
to
human
vision.

• Sensors
known
as
CCD
(or
charged-‐
couple-‐device)
and
are
made
from

silicon.

• Microscopic
grid
of
millions
of

PIXELS
(picture
elements)
held
in

thousands
of
rows.

• Electrical
signals
produced
rela,ve

to
quan,ty
of
light
received.

Light
reaching
each
photosite
releases
electrons
from

the
silicon
and
pass
through
a
transparent
gate
(G).

They
are
held
in
a
‘well’
or
pocket
(P)
that
collects

these
freed
electrons
by
a
small
voltage
passed

between
electrodes
(E).

The
greater
the
amount
of
light,
the
more
electrons

are
captured
which
creates
a
bigger
electrical
charge.

This
charge
is
converted
by
the
cameras
micro-‐
processor
to
represent
a
luminance
value:

a
low
charge
=
low
density
=
darker
part
of
the
image.

a
higher
charger
=
greater
density
=
lighter
area
of
the

image.

WHY USE A RAW FILE?
• A RAW file is a digital negative. They are image files saved directly
from the camera’s sensor without any in-camera processing.
• They retain optimal detail and more dynamic range than a JPEG,
hence offer more flexibility for editing.
• However they use more disk space due to larger file size, and each
camera manufacturer has their own version of RAW (Canon - .crw /
Nikon - .nef). Adobe have created the DNG file format (Digital
Negative) which is a universally compatible RAW file format.

WHAT IS DYNAMIC RANGE?
FIRST YOU NEED TO UNDERSTAND
SUBJECT LUMINANCE RANGE.
1:
the
clear
blue
sky
gives
a

high
‘subject
luminance
range’

-‐
from
highlight
to
shadow.

2:
the
cloud
diﬀuses
the
light
and

soUens
both
highlight
and
shadow

to
gives
a
much
lower
‘subject

luminance
range’.

WHAT IS DYNAMIC RANGE?
• The
Dynamic
Range
is
a
scale
between
the
brightest
highlights
and
the
darkest

shadows
of
an
image.
Every
digital
device;
camera,
scanner,
monitor,
printer
has

its
own
unique
DR.
Analogue
film
is
also
scaled
by
its
DR,
with
nega,ve
film
having

superior
DR
to
colour
transparency
or
slide
film.

•
Do
not
confuse
with
HDR,
or
high
dynamic
range;

a
digital
technique
based
on
digital
cameras

not
having
the
DR
of
colour
nega,ve
film.
Hence

the
digital
camera
has
to
take
three
or
more

exposures
to
capture
all
the
highlights
and
shadows.

RAW VS JPEG?
•
JPEG
ﬁles
are
smaller
so
more
can
be
stored
and
edited
faster

•
Most
soUware
programs
can
open
JPEG

•
RAW
ﬁles
contain
a
wider
DR
even
aUer
being
edited
and
adjusted

•
RAW
preserves
the
image’s
original
pixel
informa,on
–
JPEGs
contain
‘in-‐
camera’
pixel
edi,ng.

•
The
bo]om
line
is
‘ALWAYS
SHOOT
RAW’
or
pair
RAW
with
JPEG

SETTING UP FOR COLOUR BEFORE WORKING
ON AN IMAGE
• We have established new networked Mac systems which has impacted on our
colour workflow for display. This means that you need to set up your display settings
if you log in to a new computer:
• System Preferences (in dock) > Displays > Colour > UWEnov2014.
• System Preferences (in dock) > Desktop and Screensaver > Apple > Solid Colour
> Solid Gray Medium.
• Photoshop CC2014 > Edit > Colour Settings > Europe Prepress 3.

RAW VS JPEG?
•
Log
in
to
a
computer
(or
share
one
if
one
isn’t
available.)

•
Open
the
volume
‘TempStore’
on
the
desktop.
Then
open
the
folder

‘-‐Groupshare-‐’
>
folder
‘BA
PHOTO
DT1’.

• Open the file ‘DSC7943.jpeg’ in Photoshop CC 2014. Then open
the file ‘DSC7943.NEF’ using the same software.
• Compare the two images visually on the Eizo screen. What are the
differences?
• What tool in PS can we use to analyze the images?

USING HISTOGRAMS
•
The
histogram
displays
a
graph
of
the
current
light
and
dark
tonal
values.

•
The
horizontal
axis
represents
the
256
colours
or
shades
of
grey,
and
the

ver,cal
axis
represents
the
amount
of
pixels
in
each
of
those
colours.

•
The
histogram
of
an
image
that
has
been
edited
aggressively
will
have

gaps
and
spikes.
These
represent
lost
of
tonal
details
due
to
the
aggressive

edi,ng.
This
is
not
necessarily
a
bad
thing,
more
of
a
crea,ve
la,tude.

USING HISTOGRAMS
•
As
men,oned,
a
histogram
is
a
graph
of
the
tonal
range
of

an
image.
The
shadows
of
an
image
represented
on
the

leU,
highlights
on
the
right.

•
An
image
with
a
wide
tonal
range,
will
have
a
balanced

distribu,on
of
pixels
between
shadows,
midtones
and

highlights.
When
an
image’s
histograms
lacks
pixels
in

certain
areas,
there
is
a
loss
of
detail
in
the
image.

•
Images
fall
loosely
into
3
categories
based
on
tonal
image

(See
graph).
When
a
histogram
contains
gaps
and
spikes,
it

means
loss
of
shadow/highlight
detail
and
heavy-‐handed

edi,ng.

WHAT IS COLOUR TEMPERATURE?
• Is
a
measure
of
the
colour
proper,es
of
a
par,cular
light
source
(light

bulb,
match,
sunlight,
flash
light,
etc.)
calculated
in
‘degrees
Kelvin’.

Different
colour
temperatures
emit
differing
colour
casts
when
captured

either
digitally
or
by
analogue.

• Digital
cameras
have
seings
to
adapt
to
each
ligh,ng
condi,on
to
make

an
image
neutral
in
colour.
Analogue
film
has
tradi,onally
been

manufactured
with

different
chemical
proper,es
to
adapt
to
ligh,ng

condi,ons
(tungsten,
daylight).

•
What
happens
when
you
have
two
different
colour
temperatures
in

once
scene.
E.g.;
using
flash
light
in
a
room
lit
by
tungsten
light
bulbs?

Electromagnetic
spectrum
Receptors in our eyes are
sensitive to wavelengths of
radiation between:
400 - 700 nanometres
(1/1,000,000 of 1mm).
When light contains an even
mix of wavelengths we
perceive ‘white’ (or grey) light.

7
am

9.30
am

12
noon

5
pm

6
pm

6.30
pm

Thirlemere
-‐
Sun
&
Shadow
(Daylight
Film).

COLOUR TEMPERATURE GUIDE?
•
FLASH
LIGHT
–
6000K

•
FLUORESCENT
–
4K
to
5K

•
TUNGSTEN
-‐
2.5K
to
3.5K

Bulgaria
-‐
Fluorescent
&
Daylight
(Daylight
Film).

Housesteads
Roman
Museum
-‐
Mixed
Colour
temperature:
Daylight,
Tungsten,
Fluorescent
&
‘Bounced’
Flash
(Daylight

Film).

COLOUR TEMPERATURE GUIDE?
• Be aware though that, not only do different light sources have different
colour temperatures, they also emit light with different colour casts.
• Through a mixture of colour temperature filters such as CTO’s and CTB’s,
we use use colour correction filters to neutralise the casts of certain light
sources; e.g the green cast emitted by fluorescent light.

WHITE BALANCE
• A digital camera uses the process of white balancing or WB to adjust the
red, green and blue or colour temperature of an image to create an
accurate white. The camera will also have other colour temperature settings
based on different lighting conditions e.g: daylight, flash, cloud, tungsten,
fluorescent.

CUSTOM WHITE BALANCE
• To get true accurate colour balance for any image you are shooting, you
should shoot in RAW and adjust in post production, by using a White or
Grey Card/QP CARD.
• When shooting film you can also use the white card, when scanning the
film later.
• http://www.qpcard.se/BizPart.aspx?tabId=31&prod=1&catId=1

WHAT IS COLOUR SPACE?
• It is a defined range of colours in relation to a ‘chromaticity’
spectrum – an approximated range of colours as perceived by
human vision.
• On your camera and monitor, you can select a colour space for
your images to be viewed. There are many colour spaces, but there
are two that can be regarded as industry standard use:
• Adobe RGB (1998) for all edited and converting RGB to CMYK in
preparation for printing. Most lab monitors are set to this space.
• sRGB reflects a smaller space used for most web-based images.
• There is a relationship between the colour space you choose and
its colour gamut (more later).

WHAT ARE THE PRACTICAL IMPLICATIONS OF
COLOUR SPACE (RGB/CMYK)?
• RGB or Red, Green and Blue are the primary colours of light, and usually
the principal colours we view on a monitor.
• CMYK or Cyan, Yellow, Magenta and Black are secondary colours used
for all printing techniques.

So
whilst
we
view
in
‘addi,ve’
RGB
and

viewing
is
made
via
light

transmission…..

….
we
print
in
‘subtrac,ve’
CMYK
because

viewing
is
made
via
light
reﬂec,on.

WHAT ARE THE PRACTICAL IMPLICATIONS OF
COLOUR SPACE (RGB/CMYK)?
• RGB or Red, Green and Blue are the primary colours of light, and usually
the principal colours we view on a monitor.
• CMYK or Cyan, Yellow, Magenta and Black are secondary colours used
for all printing techniques.
• Some RGB colours that are viewed on screen cannot be printed to CMYK
or vice-versa.
• This anomaly is called ‘Out of Gamut’, and can be seen by viewing the
Info box, or Gamut viewing box in Photoshop.

DIGITAL CAPTURE -
FROM CAMERA TO SCANNER
• DIGI-CAMERA FILES – RAW & DYNAMIC RANGE
• COLOUR TEMPERATURE/WHITE BALANCE
• COLOUR SPACE
• COLOUR GAMUT
• SHORT ACTIVITY AROUND PRACTICAL
ASPECTS FOR PUBLICATION.
• QUICKFIRE TUTORIALS FOR WEEK 11 SESSION

WHAT IS COLOUR GAMUT?
• Every monitor, printer, paper-type has it own individual gamut, the way
any given colour space can be represented by any given output device.
• For example, you take a picture of a rainbow, the monitor represents the
colours of the rainbow as best as it can depending on its gamut, the same
applies when the image is printed onto any given paper.
• The art is to try and match the colours between each stage - camera,
monitor, printer, to bring uniformity to the image. When one of the devices is
not calibrated properly, this is where the problems start.

• The horse shape is the entire range of colour
detectable with the human eye.
• The triangle in the middle is the gamut range
of a monitor
• Each output device, paper, monitor has its
own gamut.
• In Photoshop CC2014 > Edit > Colour Settings
- what are the settings?

• Determining the ‘out of gamut’ and how best to rectify it, usually applies when we
want to print out an image and achieve the best colour reproduction.
• We can ‘soft-proof’ an image by applying the colour profile that is specific to our
output device. E.g. you wish to get a print done at a lab, the lab with have different
colour profiles for each paper type. You download the profile from the lab’s website,
and assign the profile to Photoshop. (We will cover this in detail next week, but for
now look at the Printspace’s website; www.theprintspace.co.uk)
• By soft-proofing and looking at how the RGB image looks, compared to the CMYK
profile, we can change the colours to match and get the optimal print.
• Colour management is vital to get right when you print/output you images through
different forms of media. There has to be CONSISTENCY!

SCREEN CALIBRATION AND WORKING
ENVIRONMENT
• We use calibrated screen and print output – you can request to have your laptop
screen calibrated but many machines are not built to give ‘accurate’ colour rendition.
• If you cannot get hold of a calibrator, use your monitors basic set up procedure. It
is not ideal, but remember two things:
• White point - Defines the purest white of a monitor. Set it at 6500k
• Gamma - Defines the brightness of the midtones. Set it a 2.2
Then ideally work in a darkened working environment – daylight balanced viewing
tubes.

REMEMBER: DIFFERENT COLOUR SPACES WILL
DISPLAY DIFFERENT COLOUR GAMUTS?
• Adobe RGB (1998) - This is the main space for editing images and the most
universal. It produces a wide range of colours (good gamut) and is best when
converting RGB images to CMYK prints.
• sRGB - This is best choice when you finished editing images in Adobe RGB, and
you need to convert to display on the web. It reflects the colours of an average
monitor, so your image will be consistent as it possibly can be in terms of colour
representation.

IN THE NEXT DT SESSION?
• We will be looking at capture sharpening, exporting images and bit depth.
• If you want to try your hand at colour balancing, shoot a range of images
utilising the full functions on your camera concerning colour temperature
and white balance.
• Shoot in RAW and try and shoot in different lighting conditions using
additional light sources. e.g; shoot a portrait using an on-camera flash, in a
tungsten filled room at night, selecting different colour temperature settings.
• You can use these as test images to edit and adjust colour casts and
temperatures to create neutral or colour cast images. (Not as an assessed
exercise, more of a practical exercise in understanding colour).
Take a short break and we can talk project ideas.

Digital Theory 1.pdf

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