So, here we are four versions on and Photoshop CS2
(AKA Photoshop 9.0) has its own list of changes. Thankfully the major
changes are for the better, which means that few, if any, existing
Photoshop users will be too disgruntled.
OK, so the color management system and associated
settings have been tweaked a little, but they'll still be familiar to
those who have been using versions higher than 7. All of this is good
news if you're migrating from these earlier versions. However, color
management and particularly the plethora of options associated with it
can leave many new users in a state of confusion. Therefore, the
content of this essay, is aimed primarily at new Photoshop users. Also,
since it's aimed at the newer user, I think it worth taking a few
moments to review the underlying principles of color management.
Color Management Primer
Components of a Color
Management System
A typical imaging system will consist of input
and output devices, for example: scanners, digital cameras, monitors,
and printer. Unfortunately, with such a range of device types,
technologies, and gamut limitations, it's inevitable that at least some
of them will reproduce the same color differently (i.e. color is
device dependent). Obviously, this will present significant
problems when working with documents originating from different
sources, and will be further complicated when the same document is
destined for different types of output device. Therefore, some means of
ensuring that color data is reproduced in a predictable way throughout
the entire imaging system is essential. This is where the Color
Management System (CMS) comes in, and its job is to maintain the
consistent and accurate appearance of color on all of the different
devices within the imaging system.
A color managed system comprises three basic
components, namely: -
-
A device-independent color space - this is usually
referred to as the Working or Reference color space.
-
ICC profiles for each device (i.e. printer,
scanner, monitor, digital camera, etc.) that accurately describes the
color characteristics of the specific device.
-
A Color Matching Module (CMM) that will
interpret the information contained within the device profiles and
carry out the instructions on how the color characteristics of each
device should be treated.
Color Numbers, their
Meaning and ICC Profiles
A digital image will usually comprise many millions
pixels, each of which is represented by a numeric value. The value
assigned to each pixel will describe many attributes but in this
essay it's the color value or mix (e.g. RGB value) that we're most
interested in. I have already mentioned that when a color is
device-dependent, then the appearance of pixels with identical
values will very often differ. I have also mentioned that this is
because each device has its own unique way of translating the raw color
value into visual color. This is where the ICC profiles come into play.
The ICC profile ensures that discrepancies that result from the widely
differing color characteristics of each device are known to the color
management system. In simple terms it's the ICC profile that conveys
the meaning of the raw color numbers associated with each pixel. If we
were discussing spoken language rather than color, then the ICC profile
would be synonymous with a translator.
Device profiles come in two basic forms, i.e.
Input and Output. Input profiles typically describe
the color characteristics of scanners and digital cameras, whereas
Output profiles describe devices such as monitors, printers and
film recorders. Input profiles are often referred to as one-way
since it is only possible to select them as the source meaning we can
never convert an document into the color space of our scanner or
digital camera. Output profiles are two-way meaning we can
convert From or To them.
Consumer class film and flatbed scanner applications
have been ICC aware for some time now, with the vendors usually
choosing sRGB as their preferred color space, which is a bit of a
misnomer because sRGB is not a device color space. Clearly, these
vendors are doing some work behind the scenes so as to keep things
simple for the user, which isn't necessarily as good as it might first
appear. The sRGB color space isn’t generally regarded as appropriate
for high quality image editing, especially when print or film output is
required. So, to overcome this some vendors also provide the user with
the option of choosing from a small selection of alternatives. For
example, printer vendors such as Epson provide generic ICC profiles
with their Photo class printers, although generally accepted these
profiles are rarely as accurate as we would like. Nevertheless, they
are getting better with each new generation of printer. As a rule,
truly accurate color matching usually requires customised ICC profiles
for each device and/or media type. These ICC profiles can be created
professionally or you can buy your own profiling application.
Why bother with
Profiles and Color Management?
Even though color correction and color management
are not the same thing they're often confused with each other,
especially by the novice Photoshop user. Explaining the difference can
very often lead to even more confusion, but hopefully the following
explanation provides some help.
We have already established that the color
characteristics of most imaging devices tend to be unique to that
device. Likewise, it's very rare for them to be truly linear (i.e.
R=G=B=Neutral). Sometimes this second characteristic is referred to as
the device being badly behaved; with scanners and printers being good
examples of badly behaved devices. Obviously, it would be extremely
difficult to edit a document where a group of pixels with values of
R=G=B=128 (i.e. grey) actually appeared on the monitor to be
non-neutral. In such circumstances color correction would an absolute
nightmare. To overcome these discrepancies we usually carry out all our
editing in color spaces that are well behaved or device independent. In
Photoshop well behaved color spaces are more usually referred to as the
Working Spaces, and are always characterised by RGB values that
appear neutral when all three are equal. These Device Independent
color spaces do not behave like, nor are they influenced by, any real
world device. So, in this respect it could be argued that Working
Spaces are based on synthetic color spaces.
So, we have Device Profiles and
Working Space Profiles - how do they interact?
The first thing we need to understand is that for
them to be useful to the color management system, then both device and
working space profiles must confirm with the ICC standard. In fact
you'll more often see such profiles referred to as just ICC profiles.
Anyway, without the aid of device profiles the accurate
translation of the document color data (the RGB numbers) from the
scanner or digital camera into the Working Space will prove very
difficult, if not impossible. Likewise, without the aid of accurate
media specific printer profiles, the translation from the Working
Space into the color space of a digital printer will prove equally
difficult. We also need an accurate monitor profile so as to ensure
that what we see on the monitor is a true representation of the
document color.
The following flow diagram demonstrates a typical imaging workflow,
with the document being passed between devices: - from scanner/digital
camera - to - computer - to - monitor - and printer.
Typical Imaging System
So, the main benefit offered by color management is
that the process of color correction can be undertaken in the knowledge
that the document displayed on the monitor is an accurate visual
representation of the original subject, and that the final print will
accurately reflect the colors of the document being displayed.
Some Photoshop Revision
Photoshop CS2 continues to use document specific
color settings, which means that the color space of each document is
independent of others that may be open on the Photoshop desktop. As
with previous versions of Photoshop the Working Space that's defined in
the Color Settings dialog only has a direct bearing on three
types of document, viz.: -
-
New documents
-
Existing documents without an embedded ICC profile
-
Imported documents with no embedded ICC profile (i.e. untagged
documents), which might include scanned documents or those
emanating from digital cameras.
Document specific color means that it's the ICC
profile embedded within the document that determines how it will be
displayed (it's appearance) and not the default Photoshop Working
Space. With Photoshop CS2 you can have multiple documents, each in
its own unique Working Space, open at the same time, and each
will be displayed accurately. Of course all of this assumes you're
using an accurately calibrated and characterised monitor.
Section 1 - Monitor Calibration
and Characterisation
Monitor calibration and characterisation (profiling)
is probably the most important aspect of a color managed workflow. So,
what is calibration, why is it so important, and why is it different
from characterisation?
Calibration is a process whereby a device is brought
to a standard state (e.g. a color temperature of 6500K and gamma of
2.2), whereas characterising the monitor is the process of determining
how the monitor represents or reproduces color . We characterise the
monitor by measuring how it displays known color values, then creating
an ICC profile. The ICC profile is simply a data file that includes a
description of the monitors’ color handling characteristics (i.e. its
gamut). The calibration data will also be written into the ICC profile.
As I've already mentioned, Photoshop then uses the monitor profile to
automatically optimise the display of documents. It does so by carrying
out an on-the-fly conversion between your document profile (e.g.
ProPhoto RGB, Adobe RGB, sRGB, ColorMatch) and the monitor profile.
This conversion does not alter the actual document in any way; just its
appearance on the monitor.
Tip: Adobe no longer supply Adobe Gamma
with the Mac version of Photoshop. Nevertheless, Mac users can use
Apple Display Calibrator Assistant found within System Preferences as
an alternative. A tutorial describing the process of calibrating a
display with the Apple Display Calibrator Assistant can be found
here.
To calibrate and characterise the monitor Windows
users should open the Adobe Gamma utility or a third party
alternative. If you're not already familiar with Adobe Gamma
it's a Control Panel utility that can easiest be accessed from
My Computer > Control Panel. However, before running
Adobe Gamma, it is best that the monitor has been switched on for
at least 30 minutes. It is also a good idea to work in subdued lighting
when calibrating a monitor, and remember to set the desktop color to
grey.
Tip: Adobe Gamma was designed for visual
calibration of CRT type monitors and is unlikely to produce
satisfactory results with LCD type monitors. If you're using an LCD
type display then I recommend that you purchase a hardware based
calibration system such as the X-rite Photo iOne Display 2 or
Datacolor SpyderPro3.
Windows Control Panel as is appears when using the
Classic Theme
Step-by-Step Calibration
Step 1
When the Adobe Gamma utility is first opened
you will be asked to make a choice between the Step-by-Step (Wizard)
and the Control Panel method. It's probably easier to use the
Step-by-Step (Wizard) method.
Step 2
Using the Load button choose your monitor profile or pick one
that's close, but if in doubt choose sRGB,.
Before progressing to the next step, be sure to give the profile a
unique description and include the date.
Step 3
Set your monitor contrast control to maximum and
then adjust the brightness control until the innermost grey square is
only just visible against the black surround. Squinting your eyes helps
with this process, as does keeping the room lighting at a low level or
off.
Step 4
If you're using a manufacturer supplied profile for
your specific make and model of monitor then in all probability the
Phosphors will be listed as Custom. If this is the case leave
well alone. If you don't have a monitor profile choose either
Trinitron or P22-EBU. I keep getting asked -"how do I decide
which is appropriate for my monitor?" You can tell a Trinitron
monitor by simply looking at the display area. A Trinitron type monitor
will have two faint lines running across the display area approximately
1/4 from the top and 1/4 from the bottom. If your monitor has these
lines choose Trinitron, otherwise choose P22-EBU.
Step 5
You should begin by keeping View Single Gamma
selected. However, keep in mind that this option ONLY allows you
to adjust the relative brightness of the monitor. Adjust the slider
until the inner grey square blends with the outer frame, squinting
slightly can help. Finally, deselect the View Single Gamma
checkbox.
Step 6
This is the step where you neutralise the color
imbalances inherent in your monitor. Adjust each of the sliders in turn
so as to blend the inner square with its colored surround. Again
squinting is a great help. Green is usually the most difficult to get
right, but persevere. The closer you get to a perfect match at this
point the more accurate your final profile will be.
Step 7
Depending upon your computer type choose either the
Windows Default or Mac Default gamma. In reality, this
choice is not as important as it once was and you can choose either in
the knowledge that Photoshop will make the appropriate corrections when
necessary. Personally, and even though most of my work is now done on
the Mac platform I choose gamma 2.2
Step 8
Choosing the White Point for your monitor is
pretty much a formality these days. Even the die-hards are in agreement
that 6500oK is probably the best option on most
systems.
You should have already set the Hardware
white point via the dials/buttons on the monitor. Most monitors have a
native white of 9300oK; so do check what it has been
manually set to.
Choosing 6500oK provides the
cleanest and brightest white point and closely matches daylight. If you
feel really confident you could select the Measure option. You
can choose 5000oK, but this usually produces a dimmer
and more yellow white point.
Step 9
Generally, it's better to leave the Adjusted
White Point setting at the default - Same as Hardware. Nevertheless,
this option is used to choose a working white point for monitor
if it differs from the hardware white point set in the last step.
By way of example; if your hardware white point can
only be set to 6500oK, but you want to set it at
5000oK then simply choose this value as the Adjusted
White Point setting. Adobe Gamma will change the monitor display
accordingly. However, choosing this approach will all cause the
graphics card color LUT to be adjusted quite severely, and depending
upon the graphics card the screen can look quite ugly on some systems.
As indicated above, I recommend that you choose Same as Hardware
and thus avoid this problem.
Step 10
That's it, if all has gone well you will have
adjusted the brightness, contrast and color settings of your monitor to
the optimum values.
Make a quick check using the Before and
After radio button. If you're happy that the screen display now
looks more neutral than before press the Finish button and
Save the profile. Once saved the profile will be available for use
by the OS and Photoshop.
Section 2 - Photoshop CS2 Color Settings
The Color Settings dialog is the control room
for the Photoshop colour management system, and like all control rooms
it can appear complicated. Both the dialog layout and default colour
settings have changed slightly from previous versions, but the changes
are more aesthetic than functional, so I won't dwell on them. If you
already use Photoshop then you'll likely have this dialog
configured to meet your needs, and it's probably best that you stick
with those settings. On the other hand new users should begin by
clicking on the button labelled More Options.
The default RGB colour setting depends upon your
location but generally you'll find that it's either: North America
General Purpose 2 or Europe General Purpose 2. If you're
working with documents that are primarily destined for the web then
either is perfectly acceptable. However, if you're documents are
destined for print then these settings are generally regarded as being
less than ideal. So, if the General Purpose 2 settings are not ideal,
what is?
I could answer the above question by simply writing
"US or Europe Prepress Defaults", but doing so doesn't
really help explain why. Therefore, I will work my way through each
section of the Color Settings dialog in turn.
Note the box at the bottom of the dialog labelled
Description. As the mouse is moved across the various pop-up menus,
etc. you should see a short but informative explanation of what each
menu does. Also note the button labelled More Options; it's
probably best that you select it now, as it will let you see the
complete Color Settings dialog rather than the simplified
version.
Figure 1 - Photoshop CS2 Default Color Settings
The first section is labelled Settings, and
is a simple pop-up menu with a list of preset Photoshop settings plus
any that you may have saved previously. You needn't worry too much
about this section just yet.
Figure 2
Working Spaces
The next section is labelled Working Spaces
(figure 3), and as I discussed earlier the selections made here will
determine the Working Space profiles used for colour handling of
your documents.
Figure 3 - Default Working Space Profiles
There are four Working Space types in
Photoshop: RGB, CMYK, Gray and Spot (occasionally called
Modes because they appear under the Image>Mode menu). Since configuring
the others follows a similar process I will concentrate on the RGB
Working Space.
Also note that the term Working Space should
not be confused with Workspace, which is used by Adobe to
describe the layout of palettes, menu bars, etc. Working Space
relates specifically to the various colour modes available in
Photoshop.
RGB - Working Space
Clicking the RGB pop-up menu with the mouse
will produce a list of options similar to that shown below (figure 4).
In this example I've selected Adobe RGB (1998) as the RGB
Working Space. You'll also notice that it appears grouped with
three other Working Spaces, these historically being the most
popular choices of Photoshop professionals. Typically, sRGB will
be confined to situations were the user is solely interested in web
design. ColorMatch RGB was once a favoured choice of many Mac
users and Apple RGB is apparently for Mac web design.
Figure 4
If you look just above the four common Working
Spaces you should also find options for Monitor RGB, and in
the case of Mac systems ColorSync RGB. Monitor RGB is the
colour space of your monitor as created by the Adobe Gamma
utility or a 3rd party software/hardware combination. Generally, it
isn't a good idea to use the monitor profile as your Working Space,
but it's important that does appear in the list.
It's often claimed that Photoshop CS2 has no obvious
way of informing the user which monitor profile is actually being used.
Well, a quick check for Monitor RGB in the RGB Working Space
pop-up should be enough to put your mind at rest. If Monitor RGB
is showing something other than the profile you created when
calibrating the monitor it is essential that you investigate the reason
and make the appropriate corrections.
The actual list of options available for selection
as Working Spaces different according to whether More Options
is activate, or not. If you chose to activate More Options then
the list of available RGB profiles will be quite extensive.
CMYK - Working Space
Desktop type inkjet printers from Epson, Canon and
HP actually require RGB data rather than CMYK, which
means that the choice you make for this particular Working Space
will have no influence in their actual output. This is the main reason
that I leave it set at the default US Web Coated (SWOP) v2, and
if using a desktop inkjet, then I suggest that you do likewise.
So, other than the list of available profiles, the
procedure for choosing CMYK Working Space isn't that different
to RGB. Again, having More Options activated gives you a
more extensive list.
Note: the options available to you may
not exactly match those shown in the screenshot!
Figure 5
Grayscale - Working Space
With the Grayscale Working Space we have
access to two gamma settings, a series of five preset dot gain curves,
the ColorSync Gray Work Space (Mac only) and the ability to
customise the dot gain to our own requirements. The Gray Gamma 2.2
is probably the best for most users, but feel free to experiment.
Figure 6
Also note, that if you choose to use a Custom
Gamma or Dot Gain this will be the Working Space
listed in the Gray Working Space pop-up menu.
Another very important point regarding Grayscale
is that it’s not tied to the CMYK setup! This is why some legacy
grayscale documents might not look quite the same as they did in
Photoshop 5.x (does anyone still use Photoshop 5?)
Spot - Working Space
The Spot pop-up menu is broadly similar to
the grayscale, but for spot colors. The options that we find include a
series of five preset Dot Gain options and the facility for
customising the Dot Gain curve if required. The screenshot shown
below indicates that I've selected 20% Dot Gain version as my
default.
Figure 7
Color Management Policies
Color Management Policies was a new phrase
introduced by Adobe with Photoshop 6 and continues with only minor
changes in Photoshop CS2. Figure 8 below shows the new default setup,
but this hides a lot of important information.
Figure 8 - Photoshop CS2 Default Color Management
Policies
Based on feedback, this section of the essay is
probably the one that causes new Photoshop users greatest difficulty.
Nevertheless, it's an important aspect of Photoshop that is better to
understand than ignore. Therefore, the explanation that I give below
will appear quite wordy.
Basically, each Working Space will have the
same set of three policy options, although you need not configure each
identically. The Color Management Policies are: -
(a) Off
In simple terms, the Off Policy ensures that
Photoshop does as little as possible when dealing with ICC profiles. In
most situations it isn't the ideal choice and contrary to popular
believe it's certainly not for new users. The following explanation
will give you some idea as to the behaviour of Photoshop when this
option is selected.
-
Choosing Off will mean that all new
documents will be created without an embedded ICC profile. Likewise,
when you save them there will be no embedded profile within the
document. Generally, documents that do not contain an embedded ICC
profile are referred to as being untagged, which invariably means
that their color appearance will vary on different monitors.
-
Opening an existing document with an embedded ICC
profile that matches the current Working Space means that
Photoshop will honour the embedded profile, and that this profile
will subsequently be saved with the document.
-
The default Pasting behaviour between
documents is to retain numerical values (RGB pixel values), not the
appearance. This means that no conversion between color spaces will
take place and will often lead to the pasted section of the document
taking on a radically different appearance to that of the original.
-
Opening an existing document with an embedded ICC
profile that does not match the current Working Space (i.e.
profile mismatch) will cause that embedded profile to be stripped out
of the document. The document will subsequently be saved with no
embedded profile. With this policy you'll find that the Ask When
Opening warning checkbox is unchecked for Profile Mismatches,
so a warning similar to the following (figure 9) will appear.
Figure 9
The problem with this configuration is that the user
either accepts what Photoshop dictates or doesn't open the image at
all, not much of a choice. Activating the Don't show again
checkbox is generally accepted as a good move, and will ensure that
you're no longer nagged.
(b) Preserve Embedded
Profiles (Default)
For most situations this policy offers the greatest
degree of flexibility and therefore my preferred. The following
explanation should give you an idea as to the behaviour of Photoshop
CS2 when this policy is selected.
-
Choosing Preserve Embedded Profiles means
that when you open an existing document into Photoshop, which has an
embedded ICC profile that differs from the current Working Space,
then that document and its associated profile will be left intact. In
other words Photoshop will make no attempt to convert the document to
the current Working Space; the original embedded profile will
be retained and subsequently saved with the document. Nevertheless,
even though the document and Photoshop are no longer in sync, color
space wise, the document preview will still be accurate.
-
When opening an existing image with an embedded
ICC profile that matches the current Working Space Photoshop
will take no action; the image is opened and saved as normal.
-
The default behaviour when pasting either an RGB
or Grayscale document is slightly more complex whereby the appearance
of the pasted documented will be preserved but the numbers will
change (i.e. the pixel values will change). In the case of CMYK it is
the numbers that will be retained, not the appearance.
-
If the document being opened or imported has no
embedded ICC profile (i.e. the image is untagged) then Photoshop will
use the current Working Space for editing and previewing
purposes. However, the profile will not be embedded into the document
when it is subsequently saved.
-
Creating a new document with this policy setting
means that the current Working Space is used for editing,
previewing. The associated profile will eventually be embedded into
the file when saved. However, the default Working Space
profile for new documents can be overridden in the New
document dialog.
(c) Convert to Working Space
This policy behaves in an almost identical fashion
to color management Photoshop 5. It's for this reason that many still
tend to favour it. Actually this policy isn't a bad choice but does
need to be treated with care.
-
If an existing image with no embedded ICC profile
is opened or imported into Photoshop then the current Working
Space will be used for editing and previewing. However, there
will be no profile embedded into the image when it is saved (i.e. the
resulting image will be untagged).
-
If an image is opened or imported and has an
embedded ICC profile which is found to differ from the current
Working Space then that image will be converted into, and
subsequently saved in the Working Space. When the image and
the Working Space are matched then Photoshop takes no action;
the image is opened and saved as normal. New documents will be
previewed, edited and ultimately saved in the current Working
Space.
-
Finally, the default pasting behaviour is to
convert and thus preserve the appearance of the document. However,
the user will get the option not to convert the pasted image, hence
preserving the numbers if the pasted image doesn't match with the
target image.
The following warning (figure 10) will appear if the
profile warning Ask When Opening has not been activated for
Profile Mismatches. Again, my earlier comment about Photoshop
imposing its will on proceedings applies. It's worth reading the text
and comparing it with figure 9.
Figure 10
At first glance the above warning appears virtually
identical to that shown for the OFF Policy, but there is a
subtle difference - the document is converted to the Working Space
profile rather than discarding the embedded profile. Compare the text
of the two screenshots (figure 9 and 10) if you're in any doubt as to
the differences. Again you may wish to tick the Don't show again
checkbox so as to stop this warning reappearing in the future.
Overriding the Default Policy
Behaviour
The previous section described how your choice of
Color Management Policy determined the default behaviour of
Photoshop CS2 under various scenarios. However, you need not be
confined to these preset outcomes. A much better option would be to
configure the Color Management Policies as shown in figure 11
below.
Figure 11
Here we can see that each of the checkboxes for
Profile Mismatches and Missing Profiles be set for Ask
When Opening or Ask When Pasting as appropriate Basically,
the three checkboxes associated with the profile warnings have the
following impact on the Color Management Policies: -
(i) Profile Mismatches: Ask
When Opening
When this checkbox is active Photoshop has been set
to present the user with a warning when the image being opened or
imported has an embedded profile that does not match the current
Working Space. The warning looks like figure 12, and contains three
options with the default settings being dependent upon the actual
Color Management Policy in operation at the time. Noticed that
unlike the examples shown previously, all the necessary information
required to make an informed decision is present.
Figure 12
The above example is preset for how the dialog would
appear when the Color Management Policy is set for Preserve
Embedded Profile. The user can choose to leave the image as is
(default - Use the embedded profile), allow the conversion (Convert
document's colors to the Working Space) or strip out the embedded
profile and switch off color management (Discard the embedded
profile). Had the policy been Convert to Working Space the
dialog would have looked almost identical except that it would have
been preset for Convert document's colors to Working Space.
Basically, the answer to the question: How do you want to proceed? is
already decided for you when the Embedded Profile Mismatch
dialog appears. However, if you know this answer to be incorrect then
by all means make an alternative selection, otherwise leave well alone,
and click OK.
I think you will agree that the warning in figure 12
is a lot more user friendly than the one that appears under similar
circumstances when Ask When Opening is unchecked. At least with
this option you now have the opportunity to assign an alternative
profile to the image before it opens.
(ii) Missing Profiles: Ask
When Opening
Choosing this option means that Photoshop has been
set to present the user with a warning when the image being opened has
no embedded ICC profile. The warning looks similar to the following
(figure 13) and again contains three options. The preset or default
selection is dependent upon the Color Management Policy in
operation at the time.
Figure 13
The above example is preset for how the dialog would
appear when the Color Management Policy is set for Preserve
Embedded Profile. Since no profile is embedded Photoshop will try
to assign the Working Space profile to the image. No conversion
takes place, just the assignment of the Working Space profile.
The lower Assign Profile (and the associated
and then convert to working RGB) checkbox is the best choice if you
know the source images' true color space and you want the image to
appear correctly in Photoshop. Typically, this option will be used for
images from a digital camera or similar device that does not embed a
profile in the image file or provide accurate EXIF color space
information.
(iii) Paste Profile
Mismatches: Ask When Opening
Figure 14 below shows the Paste Profile Mismatch
warning that appears in the event of the color spaces of the two images
not matching.
Figure 14
Note that the terms preserve color appearance and
color numbers relate to the source image, not the destination.
The various warning dialog boxes shown above are
only a sample of those that may appear as you open or import images
that contravene the defined Color Management Policy. However, I
think that the text messages included in each should be more than ample
to explain what each option does and will therefore allow you to make
the appropriate choice.
Conversion Options
This section will only be present in the Color Settings
dialog if the user chooses More Options. Figure 15 shows this
section of the Color Settings dialog in its default
configuration.
Figure 15
Engine: this is the name of the engine, which
will be used for all color space conversions. Unless you have good
reason to choose an alternative your should leave it at the default
Adobe ACE setting. ACE is the direct equivalent of the
Built-in engine used in Photoshop 5. Windows users should not be
tempted to choose ICM. Mac users should keep in mind that the option
chosen here will override the selection made in the ColorSync setup.
Choosing the ColorSync engine is for Mac users as a bad a choice as
Windows users choosing ICM.
Intent: this pop-up menu allows the user to
select from four different rendering intents, namely Perceptual,
Saturation, Relative Colorimetric and Absolute
Colorimetric. Typically, most users will choose between either
Relative Colorimetric or Perceptual. A short description on
each is provided in the Description section of the Color
Settings dialog. A more comprehensive explanation can be found in
the Photoshop on-line help files.
With Relative Colorimetric it is only those
source colors that are out of gamut (i.e. can't be viewed/printed
accurately within the destination color space) that will be mapped to
the closest in-gamut color, the remainder are left unchanged. This
means that in the case of images with lots of out-of-gamut colors the
visual relationship between the colors (after conversion) will almost
certainly change. With Perceptual, all colors of the source
color space will be mapped to the nearest in-gamut color of the
destination color space thus maintaining the visual relationship
between colors. In other words, with Perceptual the whole image color
gamut will be compressed so that it fits within the new color space.
The Photoshop default and my recommendation is Relative Colorimetric.
Use Black Point Compensation: this should be
kept checked. Black Point Compensation ensures that the darkest
neutrals of the source color space are mapped to the darkest neutrals
of the destination color space. In most circumstances toggling BPC
ON or OFF will result in no obvious change to the image
appearance, but in some situations converted images will look horrific
if BPC is Off, so be very careful with this setting.
Use Dither (8-bit/channel images): as with
Black Point Compensation this should be kept checked. The
description box at the bottom of the Color Settings dialog box
will give you some clue as to what it does.
Advanced Controls
As with the conversion options, this section will
only be present in the Color Settings dialog if the user chooses
to activate the More Settings option. Figure 16 shows this section of
the Color Settings dialog in its default configuration.
Figure 16
An explanation on what each of these options do is
provided in the Description box and on-line helps files. The
consensus appears to be that both settings should be left in the
default Off condition.
The Desaturate Monitor Color option is the
one that has greatest potential to cause confusion, as it will result
in the image preview to become progressively less saturated as the
percentage is increased. Those choosing to work in very wide color
spaces may find it useful, however, the majority of Photoshop users
should leave it Off.
Saving Out Your Own Default
Color Settings
Select the Save button and give your settings
a Name and Description by which you can call them back in
the future, if for some reason you make a temporary change. Also note
that you can have as many different sets of settings as you wish,
although only one can be active at a time. Figure 17 shows my preferred
color settings.
Figure 17 - Customised Color Settings Configuration
If you're using Adobe Creative Suite 2 you'll
also want to make sure that all color handling within the other
application matches with Photoshop. To help you with this task Adobe
has provided a feature within Bridge (Edit menu > Creative Suite
Color Settings) that enables you to synchronise the color settings
for all of the suite applications. Remember, that this feature is only
available when you have Creative Suite 2 installed.
Figure 18 - Synchronise Creative Suite Color
Settings
Section 3 - Soft Proofing
A frequently asked Photoshop questions is: why don't
my prints match the screen? Generally it's down to poor monitor
calibration, but on other occasions it's simply the fact that the user
has an unrealistically high expectation of what can be printed.
This section will discuss the options and commands
associated with the Soft Proof feature. As you work your way
through it you'll notice that I haven't included any reference to
specific printer driver set-ups. This is because they have been covered
in a separate tutorial
Photoshop CS2
- Managing color when printing.
So, what's soft proofing?
Basically, soft proofing is nothing more than using
your monitor to simulate a printing device. However, accurate soft
proofing is dependent upon the quality and accuracy of the monitor
profile and the media profiles for each printer/media/ink combination
that you're attempting to proof. Configuring Photoshop for soft
proofing is done via the View > Proof Setup > Custom menu as
shown below.
Figure 19
Proof Setup only affects the current or
active document on your desktop. So, if you want to define your own
default Proof Setup (a wise move) you must configure the proof
setup via the Custom menu option with no documents open.
Alternatively, if you do have a document open then hold down the
Alt/Option key to activate the ->Default (i.e. Save proof
profile) button in the Customise Proof Condition dialog.
The various proofing options are:
-
Working CMYK - soft proofs the document
using the current CMYK working space defined in the Color
Settings dialog.
-
Working Cyan, Magenta, Yellow and Black Plate
or Working CMY Plates - soft proofs the document using the
current CMYK working space defined in the Color Settings dialog.
-
Macintosh RGB and Windows RGB -
soft proofs the document using the standard Mac or Windows monitor
profile (i.e. Apple RGB and sRGB respectively).
-
Monitor RGB - soft proofs the document
using your actual monitor profile. If the document looks bad when
this option is selected you know that your monitor profile is
broken and needs to be recreated as described in Part 1.
The screenshot below shows a typical view of the new
Proof Setup (i.e. Customise Proof Condition) dialog in
CS2. In this example, I'm showing the configuration required for
simulating an Epson R2400 inkjet printer. From this dialog you can
easily select, configure and save your own customised soft proofing
setup for any number of different printer profiles.
Figure 20
You begin the process by choosing the Profile
from the Device to Simulate pop-up menu. In the example shown
above I have selected the Epson profile for Premium Glossy paper (i.e.
SPR2400 PremiumGlossy). In your case it will be the profile for the
media that you want to simulate on the monitor.
Preserve RGB/CMYK Numbers
This option will only be available when the document
and profiles are in sync, i.e. both are RGB or both are CMYK. Selecting
the Preserve RGB/CMYK Numbers checkbox will usually result in a
quite awful looking display, so don't make the mistake of choosing that
option. Basically we are simulating how the document will appear if
it's not converted to the actual device profile.
One use of this option is to enable you to see how
the document would print if the appropriate media profile is not
selected in the Print with Preview dialog. Normally it's best
the leave the checkbox unchecked.
Rendering Intent
Rendering Intent is the setting that appears
to cause most confusion and it's generally worth trying both
Relative Colorimetric and Perceptual. Typically Relative
Colorimetric will be best but some highly saturated documents will
benefit from choosing Perceptual.
Use Black Point Compensation
I described Use Black Point Compensation
previously when discussing the conversion engines. Typically, it will
be best to keep it checked.
Display Options (On Screen)
There are two options (or checkboxes) shown in this
section of the Customise Proof Condition dialog. The first:
Simulate Paper Color allows you to simulate, on the monitor, the
shade/color of the paper white. The second: Simulate Black Ink
will enable you to simulate, on your monitor, the dynamic range defined
by the media profile (i.e. how dark black will appear on the media
you're printing to). Note that selecting the Simulate Paper Color
checkbox will cause the Simulate Black Ink to be selected and
greyed out. Not all profiles will support both options.
The resulting soft proof display can be quite
disconcerting at first. By this I mean that the overall tone of the
image may tend to look compressed or slightly color shifted (e.g. white
takes on a blue cast). This can often occurs when using printer
profiles that were created from scanner based profiling applications.
In such circumstances it's probably best to leave the Simulate Paper
Color and Black Ink options unchecked.
To save the customised proof setup simply choose the
Alt/Option+Save button and give the soft proof profile a name
that clearly indicates the printer/media combination for which it was
created. The name of a saved soft profile will be appended to the
bottom of the list immediately below Monitor RGB (Figure 21
below). A comprehensive tutorial describing the technique of soft
proofing can be found at the following link:
here
Figure 21
Section 4 - Managing the
Document Color Space
As with other aspects of the Photoshop CS2 color
management system we find that color space conversion and
profile-embedding has changed little from previous versions. OK, so I
said little had changed, but now I break the news that some things have
changed. The Assign Profile and Convert to Profile
commands are now found under the Edit menu, which
isn't a dramatic change, but it does have the potential to leave those
already familiar with Photoshop a little confused.
Assign Profile
So what does Assign Profile do and when do we
use it? Assign Profile allows you to assign any profile of
your choosing to a document. The command is intended for only a few
limited uses, typically with documents that have been imported into
Photoshop using a Twain module or a scanner package that has no means
of embedding an ICC profile.
Assuming that the color management policy is not set
to Off then a document imported into Photoshop without an embedded
profile will be assigned, previewed and subsequently saved using the
current Photoshop Working Space profile. Obviously, this may not
be the most appropriate color space in which to edit or even save the
document, so assuming the you have the correct source profile you can
assign it to the document after you open/import it.
It’s important to note that assigning a profile does
not change the document (i.e. it will not change the RGB/CMYK numbers
or pixel values). Assign Profile simply provides Photoshop with
a description of the actual color space that you wish to edit and view
the document in. In other words it changes the document appearance or
meaning of the RGB/CMYK numbers.
Figure 22
-
The Don't Color Manage this Document:
option is used to instruct Photoshop to remove an existing embedded
profile (sometimes referred to as untagging).
-
The Working RGB: option tags the document
with the current default working space profile as defined in Color
Settings.
-
The Profile: popup option allows us to
assign a profile other than the default Working Space profile.
In the above example I chose to assign a customised profile for a
Nikon scanner.
Other potential uses for Assign Profile include the
removal of an embedded profile (i.e. don't color manage the document).
Convert to Profile
Convert to Profile is basically an enhanced
version of the old Photoshop 5.0 Profile-to-Profile command, the
main difference being that with Profile-to-Profile you were able
to define the source color space. In Photoshop CS2 this cannot be done
since the source profile for the image is predefined and locked. The
only way that the source profile can be changed is via the Assign
Profile command discussed above.
Figure 23
In the above screenshot I show a document with the
Adobe RGB (1998) profile embedded (Source Space) being converted to
sRGB (i.e. the Destination Space). Whenever we make this conversion it
will be the profile for the destination space that is embedded within
the document when saved. Convert to Profile changes the RGB/CMYK
numbers (i.e. pixel values) in order that the document appearance is
maintained. The Preview checkbox allows the user to compare the
conversion with and without Black Point Compensation,
Dithering, and any one of the four rendering Intents. The
ability to preview the conversion is a real boon and shouldn't be
ignored, so use it to your benefit.
Also notice that the screenshot shows the Intent
set to Relative Colorimetric. This was the default Intent
I chose when I configured the Color Settings dialog earlier.
However, as with many Photoshop setting the Intent is "sticky",
which means that if I was to change it to Perceptual then the
next time I choose Convert to Profile the Intent will be
set to Perceptual.
Section 5 - Print with Preview
Whilst printing from within Photoshop is discussed
in separate
tutorial it's still worth providing a brief overview to round
off this essay on color management.
The screenshot shown below shows the color
management options within the Print with Preview dialog box that
enable you to define the source and destination (target) color spaces
along with the rendering intent used to convert the document between
the two.
Figure 24 - Print with Preview
If you've been using a previous version of Photoshop
you'll immediately notice that we now have a more extensive and very
different list of options available. You'll also notice that
Color Management is now the default view for this dialog. Anyway,
to keep things simple I will focus on only those settings that fall
within the Print and Options area in figure X
above. I will also explain the meaning of each option and hopefully
give you better idea why certain combinations will work and others
don't: -
Print:
-
Document: denotes the ICC profile embedded
within or assigned to the source document. The example shown in
figure X shows ProPhoto RGB, but it could be any number of
user specified alternatives (e.g. sRGB, Adobe RGB (1998),
ColorMatch). If the document has already been converted to a
printer/media profile using the Convert to Profile command,
then the printer profile color space will be reflected here.
-
Proof: this field will normally display as
(Profile: N/A). Once it's activated via the radio-button it tells
Photoshop to convert the document on-the-fly from the source
documents color space to the ICC profile shown in brackets. You can
only alter the destination profile from within the Proof Setup
dialog (see: Photoshop View menu). Also, note that you'll only ever
need to use this option if you are intending to make Hard Proofs
or Match Prints (i.e. emulating another printer such as a
press), therefore I don't intend to discuss this workflow further in
this tutorial.
Options:
-
Color Handling - this is the new
pop-up menu from which you choose the preferred method of
managing color when printing from Photoshop CS2. By adopting this
approach Adobe have separated the workflow aspects of printing
from the media choices. In theory, this should make life easier for
the user, but only time will tell us whether it has. There are four
different choices: Let Printer Determine Colors, Let
Photoshop Determine Colors, Separations, and No Color
Management. Each of these choices has its own associated preset
configuration in the Print with Preview dialog thereby helping
you avoid erroneous settings.
-
Printer Profile - as its name implies this
is the pop-up menu form which you choose the ICC profile associated
with the printer/media combination you'll be using. This pop-up will
only be active when the Let Photoshop Determine Colors is
selected in the Color Handling pop-up.
-
Rendering Intent and Black Point Compensation
- again, depending upon your choice in Color Handling one or
both of these settings may be greyed out.
-
Proof Setup Preset - by default this pop-up
menu is greyed out and will only be activated when the Proof
radio button is selected. As mentioned above this option is normally
only used when simulating or proofing other output devices such as a
Press.
-
Description - this is a useful addition to
the Print with Preview dialog in so far as it provides short
explanations for each of the settings and options. The description
itself is triggered when you hover the mouse over the various buttons
and pop-up menus (e.g. Color Handling, Rendering Intent,
Black Point Compensation, etc).
Section 6 - Saving Documents
Save As
Again, whilst not necessarily part of the color
management system the process of saving your documents does involve
Save As dialog throws up a host of useful features. The Embed
Profile checkbox is very important and will reflect your choice of
Color Management Policy. You can switch it ON or OFF
as you please although the latter option is a bad idea in most
instances. Notice that the dialog even informs us which profile is
being embedded.
The screenshot shown below is how the dialog appears
on a Windows XP system; the Mac OSX version looks slightly different,
but they are functionally identical.
Figure 25
The other save options present in the dialog are
those associated with Layers, Alpha Channels,
Annotations, etc. Again, you can choose to uncheck them and so save
the image without the layers, etc. The Save As a Copy feature is
engaged by default as soon as you uncheck Layers; this prevents
you trashing a lot of hard work.
Hopefully the material presented in this essay has
been helpful and improved your understanding of Adobe's approach to
managing color in Photoshop CS2. As noted throughout the essay there is
vast body of material to be found all over the internet. A simple
search using "Google"
and the key words Color Management is all that is required.
September 2005
Whilst on the subject of things Color Management I
think it's worth mentioning a book "Color
Management for Photographers" by Andrew Rodney (aka as
the Digital Dog). This book contains a wealth of useful information,
tips, tricks and tutorials. Better still it's right up to date in that
it covers all of the changes made in Photoshop CS2. I was privileged to
have the opportunity to review the book prior to publication and would
have no hesitation in recommending it to anyone interested in learning
more about the practical issues of color management facing
photographers. Copies can be obtained from
Amazon
|
