1. What's all the Fuss About
In truth, and for many, colour management is of no great importance,
but for photographers and anyone else interested in the accurate
reproduction of colour in print or on screen, it is one of the most
vitally important features introduced by Adobe as part of Photoshop 5.
One of the most often raised
issues relating to Photoshop is – "why don’t the printed
colours match the colours displayed on screen?" Epson claim in
one of their online support documents that the answer is quite simple
- "because monitors and printers use different technologies to
create colour". They go on to say - "no monitor will ever
match the printed piece of ANY printer due to the fact that the human
eye perceives colour completely different when looking at colour
reflecting off paper or projection from colour monitors".
However, this is only partially true, by ensuring that Photoshop is
correctly configured it is possible to achieve "acceptably"
accurate colour matched prints with only minimum effort.
This article explains the
process of configuring the colour management system within Photoshop 5
for those aiming to optimise the RGB workflow required for making
prints that come "acceptably" close to matching
their on screen image when using inkjet printers from manufacturers
such as Canon, Epson and Hewlett Packard.
Obviously, in the limited
space available it is not possible to address all the issues
pertaining to colour management. For those wishing to gain a better
understanding of how colour management works within Photoshop 5 you
should follow this link to Adobes On-line Guidance Documents:-
Further information can also be
obtained from Andrew Rodney's web site at:-
The final section of this article
deals with colour correction. Although not strictly speaking anything
to do with colour management, I believe you will find it informative if
2. The Colour-managed Workflow
The purpose of a Colour
Management System (CMS) is to maintain a consistent "appearance"
of any given colour on different devices (i.e.; scanners, monitors,
printers, etc.) throughout our system. In order that we may achieve
this it is first necessary for each device to provide the Photoshop
Colour Matching Engine or Module (CMM) with some information on how
colour behaves within that device, and this is provided through "Device
A typical "Colour-managed
Workflow" will involve image input via a scanner or Photo CD,
being viewed on the monitor, with colour correction of images on the
computer, and image output to a printer or film recorder. As the image
data is passed along the chain - from scanner - to - computer - to -
monitor - and printer, colour inaccuracies will be introduced. These
inaccuracies result primarily from the widely differing colour spaces
or gamut's of each device. To minimise these inaccuracies we must give
the CMS information in the form of device "Profiles" that
describe the colour gamut of each device. Using these profiles the CMS
is provided with information that says for example, "this RGB
image data is from such and such a scanner, which sees colour in this
way", the CMS will then know exactly what colour really looks like on
that scanner. Likewise for our monitor or printer, again with suitable
profiles the CMS will adjust the scanner image data into a form that
the monitor or printer can show accurately.
Most devices are supplied with
generic or "Canned" profiles that describe them pretty
well, but for truly accurate colour matching you should seriously
consider either getting "Customised" profiles for each
device done professionally or buying your own profiling software (e.g.
ColorVision Photo/OptiCAL, Praxisoft WiziWYG or Monaco Systems
A Typical Colour Managed
It is also worth pointing out
that whilst most low cost, consumer based film and flatbed scanner
applications are ICC aware they tend to impose sRGB as the "Source"
colour space. This colour space is not ideal for anybody
seriously interested in obtaining high quality prints or film output
from within Photoshop, in so far as its colour gamut is so
limited. Some manufacturers i.e. Nikon, Polaroid and MicroTek allow us to scan and save our images in any
we choose. Unfortunately others make similar claims but in reality the "Source"
colour space is
generally always "sRGB". Furthermore, the image is rarely
if ever "tagged" with a profile of any description, so the
file contains no information relating to the profile upon which it is
3. Monitor Calibration
Having first installed
Photoshop 5 on your computer the next task is to make sure your
monitor is properly calibrated. If the monitor is not correctly
calibrated then we can have no confidence in the on screen colours
being a true representation of the image data. Accurately calibrating
your monitor is also an essential (if not critical) first step in
developing a colour-managed workflow. For real accuracy we would
normally wish to use a specialist hardware device, but these tend to
be expensive. However, Adobe has provided us with an acceptable
software solution for this purpose, namely "Adobe Gamma",
although others are available see (http://www.colorcal.com)
The following information
concerning monitor calibration is applicable only to Windows 98,
Windows 98 Second Edition and Windows 2000. Users of Mac systems may
find the procedure to be identical, but the dialogs will look slightly
"Adobe Gamma" can
be accessed either through the Windows Control Panel Folder or via
Photoshop's Help Menu and selecting "Colour Management".
To be honest I don't like the Help version of accessing Adobe Gamma
since part of the process involves overwriting ALL the hard work of
RGB setup etc. (see later).
"Adobe Gamma" is used
to calibrate your monitor at "System Level" and thus
ensures that unwanted colourcasts associated with your monitor are
eliminated. The profile created as part of the calibration process
becomes the "default profile" for your monitor and is also
available for all other applications that can use ICC profiles. This
new "Custom" profile is generally referred to as your
Space", and is unique to "YOUR" monitor. It is
important to note that:- no matter what software application you are
using, the image on screen is always being viewed in "Monitor
A further point worth
considering is your working environment. Calibrating a monitor during
daytime and using it later in an artificially lit room is pointless,
since your perception of colour in natural light is entirely different
from that in artificial light. So consider carefully how, where and
when you set up your system. A consistent environment is an essential
prerequisite for accurate colour matching.
You should use a neutral
background for the Windows desktop, and all screen savers and power
management features should be turned off (and kept “off”). Allow
at least 30 minutes after first switching on your monitor before
commencing the calibration process. Set the white point of your monitor. This is a hardware adjustment, and how you do it depends on the monitor you are using. Most monitors have a control panel. If you're unsure how to set the white point on your monitor, consult the documentation that came with it.
Before we begin the process of
calibrating the monitor check to see if "Adobe Gamma
Loader.Exe" or a short cut to it is in your "Start Up"
Folder. The Windows 98/98SE Start Up folder is nested below the
"windows/start menu/programs/startup" folder.
For Windows 2000 things are a
little more complicated in that the "start up" folder is found deep down
the tree in the "Documents and Settings" folder, and
worse still each user has his/her own set of folders - you'll need to
find it yourself!!!
If after checking you can't
find "Adobe gamma Loader.Exe" in the relevant folder;
then you can make a "Shortcut" to the file, it is
found in the "Program
files/Common Files/Adobe/Calibration" folder (this assumes
Windows based computer).
The following page outlines
the various steps in calibrating your monitor based upon Adobe's
recommended procedure and my own experience.
Step by step monitor
calibration using Adobe Gamma
opening Adobe Gamma I recommend selecting the Step By Step
or (Wizard) option. You should then follow the on screen
Adobe Gamma then
tells us the profile upon which the subsequent calibration process
will be performed.
Profile selection dialog for Photoshop 5.5
Searching out a
Profile specific to make and model of monitor is to a very
large extent a waste of time, most are pretty awful, so if you
don't have one don't panic.
Normally the first
time you use "Adobe Gamma" the profile
initially offered is the standard "Adobe Monitor
Profile". We don’t have to accept this profile, we
can actually select any monitor profile we want, but
realistically it’s as good a starting point as any. In fact
if you are using Adobe Photoshop V5.5 it is MOST DEFINITELY
the place to start. Without going into unnecessary detail it
is recognised that many manufacturer based monitor profiles
are incompatible with the Photoshop 5.5 version of Adobe
Gamma. In fact this is one of the reasons underlying some
people finding it virtually impossible to get a good
screen-to- print match. If you have a version
of Photoshop prior to V5.5 then the problem with Adobe Gamma
and manufacturer supplied profiles shouldn't be a problem.
Windows 98 and 98
Second Edition - folder named windows/system/color
Windows 2000 -
sub-folder named system32/spool/drivers/color
Mac - ColorSync
profiles are located in the System Folder/ColorSync Profiles
The dialog window shown above is unique to Photoshop 5.5 in
that earlier versions don't have the "Description"
window. This new window is actually quite important in that
you can edit the monitor profile name. In fact I recommend
that you do precisely that, otherwise the name shown will stay
with the profile and cause you utter confusion next time open
the Photoshop (e.g. - "Photoshop my profile says
its sRGB, but I know it isn't"). Simply type the new name for your monitor
profile and then select "Next".
If you have already
calibrated your monitor using a manufacturer based ICM profile
and would prefer to recalibrate
using the above method then simply remove the old monitor
profile from the relevant location as indicated below:-
The amount of adjustment required in the
steps that follow will vary, depending upon how far your
monitors’ actual behavior deviates from this initial
The next step is to adjust the contrast and brightness levels
of your monitor.
My recommendation is that
the brightness should be adjusted so that the inner square is
only just visible (as an aid I suggest that you squint when
you make this adjustment). If the on screen image looks a
shade dark after this stage don’t be too concerned, it will
be corrected during the gamma adjustment stage. In fact, I
have found that unless the screen is dim (at this stage), then
the likelihood of over dark prints is increased significantly,
so be warned!
the brightness and contrast have been adjusted we move on to
the monitor phosphor selection.
We can either accept
whatever is offered up in the window, not a good idea, you
should select Trinitron or P22-EBU, both of which are
based upon standard monitors. Although, it is fairly widely
accepted that Trinitron is probably the better starting point.
The amount of adjustment required in the steps that follow
will vary, depending upon how far your monitors' actual
behavior deviates from this initial profile.
You can also choose "Custom" and insert our own values; normally you
would need to have obtained the values from the manufacturer,
not and easy task, and pointless. Don't forget that using the manufacturers ACTUAL
ICM profile in Photoshop 5.5 is fraught with
Custom Phosphor data
Next we adjust the gamma slider (I suggest that you stick with
the single gamma option initially, just to get the hang of
things). When adjusting this slider I recommend that you sit
back about 3 feet from the monitor and squint your eyes. When
the inner square matches the outer patterned frame, stop.
Choose your desired gamma (usually 2.2 for Windows) and then
fine tune the gamma slider. If all has gone well your screen
should now be reasonably bright, but not to bright.
A common misconception
is that the gamma must be set to 2.2. Please note that there
is no absolute requirement that the gamma be set to this
value. If the user prefers to select a gamma value of 1.8 then
that is perfectly reasonable choice, it is also the case that
many actually prefer to calibrate their monitors to a gamma of
1.8 when CMYK prints are the final output medium. Mac users
will generally find 1.8 is the more appropriate choice for
their systems since it is apparently the native gamma of Mac
monitor. I use both Mac and PC and find that I personally
prefer Gamma 2.2 is the most appropriate.
become confident in using the single gamma option you can try
the 3 channel option and balance each colour channel
independently, this actually the best way. The procedure for
balancing the inner and outer squares is the same as described
above, although many people find it difficult at first to get
the "green" square right.
If you are in any
doubt about the accuracy of the "Hardware White Point"
you selected on the monitor control panel at the beginning
then it might be better to
use the "Measure" option (ensure that the room
lights are off for this adjustment).
Adobe Gamma Monitor
Colour Temperature Adjustment
The idea of the colour temp screen is to get the centre
square as near neutral grey as possible. Keeping a Kodak grey
card to hand can be helpful, but not essential.
For the "Adjusted White Point" it is normally accepted
practice to choose "6500K"if using a PC or Mac. As was the case with
gamma, it is not essential that we follow conventional wisdom
when it comes to setting the White Point of your monitor. I
have found a more appropriate choice to be "Same as
Hardware", since this doesn't actually require the
video card to make any colour table adjustments (see Real
Word Photoshop 5).
Preferred choice for
Adjusted White Point
of the monitor calibration process is to "Save"
your new monitor profile. Remember this is now the profile
that defines your "Monitor Space" and is used by
all your software applications, including most scanner
software, whether be it be "Standalone" or a
4. Colour Settings
The previous section
concentrated upon how we see colour on the monitor and how
accurate that representation of colour actually is. The "Color
Settings" menu option found under the "File"
menu is where we effectively tell "Photoshop"
what red, green, blue, cyan, magenta and yellow actually look
like, and how we want the colour management system therein to
operate on these colours.
(i) RGB Setup
The RGB setup dialog is
where we define the Photoshop RGB "Work Space".
Just to confuse matters it’s also known the "Editing
Space", or "Colour Space", I'll be
using the three terms interchangeably.
The work space selected
here is normally considered "device independent"
(i.e. independent of scanner, monitor or printer devices), and
allows Photoshop to attach a specific colour meaning to our RGB
Remember also that
unless you specify otherwise the RGB work space (profile)
selected by you here is the profile that will be saved with your
file (i.e.; "tagged").
Before we begin
selecting our preferred RGB work space I will dispel a commonly
held misconception, namely that the gamma and white point
selected for the RGB work space must be the same as we have
chosen when calibrating our monitor, wrong!, simply because the
two are NOT related. There is absolutely no reason why
you should keep both compatible.
There are nine "Canned"
RGB colour spaces supplied as standard with Photoshop 5, each of
which is based upon industry standards. There is also the option
to select your "monitor space" (i.e. Monitor
RGB) or define your own "Customised" RGB work
The selection of Monitor
RGB is not recommended since it is not "device
independent", but most importantly, monitors cannot
display a considerable part of the gamut of CMYK output devices
such as our inkjet printers.
Of the nine "canned"
RGB colour spaces there are only three that are truly useful to
most of us printing to inkjet printers, namely:
Adobe RGB (1998)
– based upon a gamma of 2.2 and a White Point of 6500K,
which is broadly compatible with daylight in shade. This
colour space comes very close to encompassing the entire CMYK
gamut, although it has some difficulty with greens. Its
gamma value of 2.2 ensures adequate separation of shadow
detail is maintained.
– this RGB colour space is based upon a gamma of 1.8 and a
White Point of 5000K. It is also widely used by Mac users,
and has slightly narrower colour gamut than Adobe RGB. Its
main drawback relates to the gamma value of 1.8, which can
cause some posterisation problems in shadow areas. That said
it is still a perfectly acceptable workspace on either the PC
or Mac platforms.
sRGB – this
RGB colour space is similar to Adobe RGB above in that it is
based upon a gamma of 2.2 and a White Point of 6500K.
However, the colour gamut of this space is somewhat limited
and can only be recommended for use with the 4-colour range
of inkjet printers from Epson, Canon, HP, etc. It is also
widely used for web pages, etc.
With the "Custom"
option we can define our own RGB colour space, although this
doesn’t come highly recommended. That said there is one custom
colour space that has almost become an industry standard, i.e.
"BruceRGB". The specification for this work
space is as follows:-
Point = 6500K
Primary xy = 0.6400, 0.3300
Primary xy = 0.2800, 0.6500
Primary xy = 0.1500, 0.0600
This colour space has all
the advantages of Adobe RGB (1998) but doesn’t suffer the
problems associated with greens to the same extent. This colour
space is now highly favored by users of the 6-colour consumer
inkjet printers such as those supplied by Epson.
Remember to use the
"Save" button after you create this profile
(this will ensure that it is retained for future use). You can
give the profile any name you like, although I recommend
BruceRGB, especially if you propose to share your files with
others, since there’s a greater chance that they will be able
to handle your file without conversion.
The last setting that
you can make in the RGB setup dialog is – "Display
Using Monitor Compensation" (DUMC). With this
feature activated we are instructing Photoshop to carry out an
"on-the-fly" conversion of the image data from
our selected RGB "work space" to our "monitor
space", using the information contained in your
customised monitor profile. So now we see why it is so essential
that the monitor be calibrated correctly. It should also be
noted that this "on-the-fly" conversion does
not impact upon, or damage the image data in any way.
If you find that your prints don't match the monitor
image (i.e. to dark, to light, etc.) then try switching DUMC
off. If the screen more closely matches the print with DUMC
off then your monitor calibration is "broken". I
recommend that you try the method I described for monitor
calibration which is based upon the "Adobe Monitor
users who share files with others, and especially across
platforms (PC to MAC and vice versa) the following should be
"If you open a
file that has been colour adjusted in a gamma 1.8 workspace
into a gamma 2.2 workspace without conversion the resulting on
screen image will appear darker and more contrasty than it
would have otherwise have done. Conversely, if you originally
colour corrected a file in a gamma 2.2 workspace and then open
it in gamma 1.8 workspace without conversion then the image
will appear flat and light."
The moral here is that
unless you have very good reasons stopping you converting to
your own workspace then you should always allow the colour space
conversion to take place.
(ii) CMYK Setup
For the most part this
dialog is of no interest to those of us who concentrate solely
on an RGB workflow. That said there is one "gem"
buried within the CMYK settings dialog that anyone using "Custom"
printer profiles simply must take heed of, i.e. "soft
proofing" your RGB printer. Unfortunately, it doesn’t
appear to work too well with Epson’s new "Standard"
Soft proofing your RGB
printer is based upon a very complex procedure developed by Mark
Hamburg of Adobe, my thanks to Andrew Rodney for giving us
access to the Photoshop Actions that make the whole process much
simpler to implement.
So, rather than try to
explain it myself I’ll let Andrew Rodney do it for me: -
5 has no RGB soft proof (unlike the CMYK Preview/Soft Proof
feature). That means that while having a calibrated display
is VERY important, you are not looking at your RGB file with
an output simulation. There IS a way to trick Photoshop into
providing a soft proof for RGB files and you will generally
see a much closer screen to print match. This is mostly
affecting out of gamut (very saturated) colours. The process
of converting an RGB output file into a CMYK profile for
soft proofing is long and complex. However, you can find a
PDF with the recipe and a Photoshop action on my Web page:-
allows you to load into the CMYK setup, a modified RGB
profile for your printer and then use the CMYK preview (Ctrl+Y)
to redraw the screen to get a closer match. Of course the
quality of all this depends on the quality of the output
profile and how well your display really is profiled and
(iii) Grayscale Setup
This dialog allows us to
define our grayscale working space by stating whether it is
based on RGB neutral values (i.e. equal values of Red, Green and
Blue) or simply based on Black ink. If the latter is chosen then
the dot gain curves defined in the CMYK dialog are used.
Remember to switch "Off" RGB soft proofing
feature described above if you are using that feature.
If you are using a
"Custom" printer profile there is a lot of
merit in converting your grayscale images back to RGB before
outputting to the printer. Although, it is worth trying both
options, and settling one you prefer rather than blindly
following convention or even my suggestions.
(iv) Profile Setup
I’ve heard it said
that unless you share your image files with other users or have
been using an earlier version of Photoshop then the Profile
Setup feature is surplus to requirements, nothing could be
further from the truth.
The Profile Setup dialog
is in fact fundamental to determining how (or even whether)
Photoshop acts upon images when they are "opened"
or "saved". If you set the various options
incorrectly you could potentially destroy an image and never
even know that you’ve done so.
It performs two
> It offers you a
method of ensuring that images get converted into your
working space, and
> It lets you embed an
ICC profile (or "tag") within the file that
describes the workspace in which the image was created.
As can be seen from the
screen-grab below, the dialog is separated into three distinct
sections, "Embed Profiles", "Assumed
Profiles", and "Profile Mismatch Handling".
The Embed profiles
section is fairly straightforward in that by checking the boxes
we are effectively telling Photoshop to automatically embed our
workspace profile within the file when we save the image. By
default all the checkboxes are normally "On".
It is recommended that you leave this section of the Profile
Setup in its default state, the exception being when you open a
printer calibration Test target (typically those used with
Device Profiling Packages such as WiziWYG, EZcolor, etc.). With calibration targets it essential that you
don’t allow the image to be saved (usually by accident) with
your work space profile, so its better to be safe than sorry,
with printer calibration images make sure "Embed
Profiles" is "Off". However, remember
to set it to "On" again once you finish with
the printer calibration.
The settings you see in
the screen-grab below are generally accepted as the safest
choices (although not necessarily the defaults that you will
obtain when you first install Photoshop, so please check), and
will enable you to avoid virtually all image data damaging
scenarios that you may encounter when opening files from
whatever source. One interesting point about Embed Profiles
and certainly one to keep in mind. If you deselect the option then
Photoshop (so far as I know no other program does this) WILL embed
a profile, but this profile will be a special profile indicating to
Photoshop that the user made this choice. When you open such an image you
will NOT get any warning messages, etc., this is quite deliberate
and also a good thing.
Profile" section is where we tell Photoshop how it
should deal with images that contain no embedded profile.
It doesn’t actually do very much other than flag up the "Missing
Profile" dialog as shown below, and even this only
happens when you open an actual image. Of course if we have set
the "Profile Mismatch Handling" section to
something other than "Ask When Opening", it
will totally ignore the fact that the file has no embedded
profile and open the image in a colour space previously specified
by you in the "Assumed
Profile" RGB pop-up
window. So it is important that you ALSO adhere to the following
advice on "Profile Mismatch Handling". You
should consider the "Missing
Profile" and "Profile Mismatch Handling"
sections as "safety nets", they're designed to slow you
up and make you think.
In the example below the image contains no embedded profile, if you
don't know the source then select "Don't Convert". If you
do know the source then make that the selection in the "From"
pop-down window then choose "Convert". Typically an image
scanned outside of Photoshop will cause this dialog to appear. If the appearance
of the image changes drastically in colour or density you made the wrong
choice, you can use Photoshop "History" to get you back
to original image.
Example - opening an image with
"no" embedded profile
The final section of the
Profile Setup dialog is the "Profile Mismatch Handling"
section. Get the settings in this section wrong and, your image
data is very likely to end up in a less than optimal state. For
each of the three pop-up windows we have three choices, "Ignore",
"Ask When Opening", and "Convert".
Taking each of the
options in turn:
– This option simply opens the image in your current RGB,
CMYK or Grayscale workspace without any conversion of the
image data. At first this may appear to be a perfectly
reasonable choice, but note, by not allowing a colour space
conversion we are in fact changing the "Colorimetric"
meaning of the image data thus it will appear on your
monitor and print differently from what it would have done
on the system in which it was created.
When Opening" – With this option, if
you open an image that has the no profile embedded
within it, you will be
presented with dialog similar to that shown above. If the
file has an embedded profile, but it's the wrong profile,
then you will get the dialog shown below. It will be displayed in the "From"
pop-up window. The "To" pop-down window will
usually be "YOUR" actual Photoshop "RGB", "CMYK",
or "Grayscale" colour space depending upon which mode,
etc. you are currently working.
to ----- C" – This is the most dangerous
option in that it allows Photoshop to automatically convert
the file you are opening "From" and "To"
the colour spaces you specified in the "Assumed
Profiles" section. For most this is not the best
option for very obvious reasons (e.g. a calibration image
will automatically be converted into your current work space
thus destroying it).
Example - opening an image with
the "wrong" embedded profile
The example above shows that the embedded profile within the image is
"Adobe RGB (1998)", since the Profile Mismatch dialog appeared
we must make one of two assumptions depending on the workspace you're actually
1. You are using a colour space other than "Adobe RGB
(1998)", e.g. ColorMatch, sRGB, etc.
2. The profile is NOT what it claims to be. This actually occurred
with the original Nikon version of BruceRGB, so don't dismiss it as a
If the dialog appears,
and unless you have very good reason to do otherwise it is
recommended that you leave the Engine: at "Built-in",
Intent: at "Perceptual Images", and "Black Point
Compensation" at "On" at all times.
the "Missing Profile" and "Profile
Mismatch" dialog boxes are designed to WARN
you that something is amiss, they will only appear when you open
an actual image, and not when you are configuring "Profile
specifically part of the Color Settings menu, "Profile-to-Profile"
(P-to-P) does form an essential part of the colour management
system, and is found under the Image/Mode menu.
Profile-to-Profile is a very powerful tool in that it
effectively lets you convert an image between any two colour
spaces, as and when required. However, there is also a "Health
Warning" that needs to be considered – "Photoshop
does not keep track of any colour space conversions undertaken by
P-to-P", which means that the user could potentially
save an image with the wrong colour space profile (tag)
embedded within it (remember, that unless you specify otherwise
the profile saved with an image will be that of your current
Photoshop work space).
pop-up is where we select the "Source" colour
space and the "To" pop-up the "Target"
It is also generally
recommended that in Profile-to-Profile mode you specify the
specific "To" and "From"
spaces (e.g. From: LS2000Scanner - To: Adobe RGB (98) rather
than From: LS2000Scanner - To: RGB), even if Adobe RGB (98) is
the colour space you have chosen in the RGB setup dialog as your
Note: It is normally
best to keep "Black Point Compensation"
Unchecked when converting from scanner profiles.
three main functions:
As a time saver,
whereby we find, that having opened a file without colour
space conversion we realise that we should have done so. By
using P-to-P we can avoid closing the file, shutting
down and restarting Photoshop.
We can also use it to
convert between the native colour space of our input devices
(e.g. scanners) and our current workspace. I mentioned
earlier that some scanner manufacturers (e.g. Nikon LS2000
and LS 30 film scanners) allow you to scan images in the
devices native and usually very wide colour space. The
problem is that Photoshop has no idea what colour space the
image is in because there is no embedded profile, and worse
still no equivalent to "Profile Mismatch"
or "Missing Profile" for images imported
via Acquire mode (i.e. "Twain" or "Plug-in"
modules). So in this situation we must force the colour space
also note that quite often a P-to-P using the devices "Native"
or even "Customised" profiles could result
in quite dramatic shifts in colour, hue and saturation. This
usually occurs if you have made colour and gamma adjustments
within the scanner software. Remember, if you propose to use
device profiles within your scanning workflow then you must
never make colour adjustments within the scanner software.
Remember also that, what you see in the scanner Preview
window is based on your "monitor space" and
bears no resemblance to the actual colours, etc seen by the
scanner. So if you carry out your colour adjustments within
the scanner software I recommend you use your monitor
profile in the "From" pop-up window of the P-to-P
dialog and not the scanner profile, be warned!
The one rider to my previous statement regarding the need to
use P-to-P when scanning into Photoshop is if you use
software such as LaserSoft's SilverFast, or on your scanner
software is designed specifically to integrate with the
Photoshop CMS, which is unfortunately still a very rare
occurrence, NikonScan 2.5x being an exception. When
configured correctly such software will allow wysiwyg previews.
6. Colour Wheel and Colour
Again, whilst not
strictly speaking part of colour management I have decided to
include some basic information on the subject of colour
correction techniques. These are not unique to Photoshop; in
fact much of my colour theory has been gleaned over a period of
twenty years printing Cibachrome prints in a conventional
During those years it
has never ceased to amaze me, how some supposedly intelligent
individuals just came apart (mentally) at the thought of even
trying to identify and correct a colourcast. So before I begin
here’s what I consider to be one of the best presentations of
the RGB/CMYK colour wheel that I have yet to come across. This
diagram has been copied from a book (classified by me as a must
have book) entitled Photoshop 5 Artistry, by Barry Haynes and
Wendy Crumpler. I know it’s a breach of copyright, but just
think of the free advert I’ve just given them .
RGB to CMYK Colour Relationships
significance of both colour spaces; RGB is what we see on our
monitor and CMYK are the inks used to create the various colours
Before we look at the
diagram in use let’s deal with another issue that seems to
cause confusion – the term "complements". As
the diagram shows:-
is the complement of
the complement of Magenta,
is the complement of
What does this mean?,
simple; by reducing "red" we’re actually adding
"cyan". By increasing "magenta" we’re
reducing "green", and so on.
So what makes the above
version of the colour wheel so good? Well just look at the
relationships between RGB and CMY and how they are specified.
Most of us (me included)
appear to have some difficulty in specifying a cast in one of
the CMY colours but virtually none when it comes to specifying a
cast if it’s "red", "green" or
"blue" biased. So in this context I will let you
decide how to interpret the diagram yourself, but remember we
all make mistakes, and its only through finding the appropriate
correction through trial and error that we will ever learn the
true art of colour correction. One "Tip" though, it is
always preferable to make colour adjustments that effect one
colour rather than two, think about it!
At least with this
diagram there’s a better chance that we can quickly establish
the most appropriate correction. I hope it makes the task of
determining the bias of a colourcast all the more easier for you
in the future, so please feel free to Print the diagram and pin
it to your workroom wall for reference.
When it comes to actual colour correction inside Photoshop I think most novices find the
"Variations" or "Color
Balance" dialogs to be the easiest to get to
grips with. However, they don’t really provide you the level
of control required to make accurate colour adjustments. On many
occasions you will find that the colour cast in say the shadow
region is one colour and the cast in the highlight another
The best option for colour correction in that situation is to use
the "Curves" tool, I know it’s a
complicated tool to use, but the sooner you learn to use it, the
sooner you will produce top flight colour corrected images. You
may also find some benefits to be in using the "Selective
Color" controls. I have found two books of
particular benefit when trying to perfect the art of colour
world Photoshop 5, by
David Blatner and Bruce Fraser,
5 Artistry, by Barry
Haynes and Wendy Crumpler
Both books offer a wide
range of advice on all things Photoshop and should form a good
foundation upon which you can further develop your knowledge in