Colour Management Primer
Ever since the beginning of colour reproduction, colour management has
existed in one form or another. The basic concept underlying Colour
Management is to ensure that colour data is processed in a consistent
and predictable way throughout the entire imaging workflow. A typical
Imaging System will consist a wide range of Input and
Output Devices, and each device will reproduce colour differently.
This means that a colour represented by one device will rarely if ever
match the same colour represented on another device. In other words,
colour is Device-dependent. So expanding upon our earlier
definition we can say that the purpose of a Colour Management System
(CMS) is to maintain the consistent and accurate "appearance"
of a colour on different devices (e.g. scanners, monitors, printers,
etc.) throughout our imaging workflow.
Components of a Colour Management System
In order that we can achieve the above aims a colour managed system
will require three basic components, namely: -
A device-independent colour space - this is usually referred
to as the Working Space or Reference Colour Space.
ICC/ColorSync device profiles for each device (printer,
scanner, monitor, digital camera, etc.) that describe the colour
characteristics of the specific device.
A Colour Matching Module (CMM) that will interpret
the information contained within a device profile and carry out the
instructions on the way the colour gamut of each device should be
The following diagram demonstrates a typical "colour-managed
workflow" and shows the image being passed along the chain -
from scanner/digital camera - to - computer - to -
monitor - and printer with the ICC profiles
ensuring that the colour data from/to each device is correctly described.
Colour Numbers, their Meaning, and
A digital image will comprise pixels each of which is represented by a
number. This number will describe the location of the pixel within
the image and its particular colour value (typically an RGB
value). We have already noted that since colour is device-dependent the "appearance"
of each coloured pixel will vary for each device. We also noted that this
is because each device has its own unique way of translating the raw
colour value into visual colour. To minimise the discrepancies that
result from the widely differing colour characteristics of each device we
use the device profiles to inform the CMM how the colour values
produced by that device should actually appear. This may be on our
monitor, in print or on film output. In simple terms it is the device
profile that conveys the "meaning" of the raw colour numbers
associated with each pixel.
Whilst "Consumer "class film and flatbed scanner software
applications are now ICC/ColorSync aware they tend to be based
upon sRGB, likewise consumer digital cameras. This colour space is
not normally regarded as appropriate for high quality image editing,
especially when print or film output is required, but is quite often all
we can expect to get. We should not confuse matters by assuming that the
scanner or digital camera is an sRGB/Adobe RGB device - they most
certainly aren't. The fact that the image delivered into Photoshop by the
scanner or digital camera application software is already in a
device-independent colour space means that it has already undergone a
considerable amount of data processing.
Some digital hardware vendors allow scanning/capture of images in any
user selected "working space" colour space. Unfortunately, the
image is rarely delivered into Photoshop with an embedded ICC/ColorSync
profile, which can lead to confusion and error.
Device profiles come in two basic forms, i.e. "Input"
and "Output". Input profiles typically describe the colour
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 image into the colour space of our scanner or digital
camera. Output profiles are two-way meaning we can convert "From"
or "To" them.
Many "Prosumer" class scanners and digital printers are now
supplied with some form of generic or "canned" profiles. Whilst
these profiles are useable they are rarely accurate. For truly
accurate colour matching you should seriously consider getting "Customised"
profiles for each device and/or media type. These profiles can be created
professionally or by buying your own profiling software. Sadly very few,
if any digital camera vendors have adopted the "canned" profile
approach instead opting process the images into a device-independent
colour space as discussed above.
Why bother with Profiles?
Even though colour correction and colour management are not the same
thing they are often confused with each other, especially by the novice
Photoshop user. The colour characteristics of most imaging devices are
such that it is very rare for them to be truly linear (i.e.
R=G=B=Neutral). Sometimes this characteristic is referred to as the
device "not being well-behaved". Scanners and printers are good
examples of "badly behaved" devices. Obviously it would be extremely
difficult for a Photoshop user to edit an image where a group of pixels
with values of R=G=B=128 (grey) actually "appeared" to be
non-neutral. In such circumstances colour correction would be an absolute
nightmare. To overcome these discrepancies we usually carry out all our
editing in a colour space that is well-behaved. Well behaved colour
spaces are more usually referred to as the "working space", and
are always characterised by having R=G=B appearing neutral.
Without the aid of accurate device profiles the accurate translation
of the raw colour data (the numbers) from our scanner/digital camera into
the working space will prove very difficult, if not impossible. The
translation from the working space into the media specific colour space
of a digital printer will prove equally difficult without the aid of
media specific printer profiles.
So the benefit offered by colour management is that the process
of colour correction can be undertaken by the user in the
knowledge that the image displayed on their monitor is an accurate
visual representation of the original subject, and that the final
print will accurately reflect the colours of the displayed image.
What changes have been made to colour
"EXIF" is a familiar term to many digital camera users, but
until Photoshop 7 it had little use. EXIF is a standardised format
agreed by various digital camera vendors for incorporating data such as
the exposure time, aperture, lens, picture resolution, colour space, etc
into the image file. However, Photoshop 7 now reads the EXIF
information embedded within the JPEG format images captured by
digital cameras and can also write new information to the EXIF
file. There are a number of quirks in the way Photoshop 7 manages the
colour space of these image files, and so those already familiar with
Photoshop 6 should be prepared for a few surprises.
The screenshot below is presented for those readers who've never seen
EXIF data before. I captured the information file from the new
File Browser window but you can also get it by selecting "File
Info > EXIF" from the Photoshop File menu.
So far as colour management and Photoshop 7 are concerned EXIF
holds some useful information (circled red in the screenshot), and this
information. The first piece of information is the potential
availability of an embedded "Colour profile" that describes the
actual colour space of the image. The second is the EXIF "Colour
space" to be assumed in the event of no colour profile being
embedded. The embedded colour profile can be anything the camera vendor
chooses to allow or nothing at all. At time of writing this essay it
appears that only Nikon have chosen to allow embedding of colour
profiles, and so many users will never see an embedded profile. On the
other hand the EXIF colour space appears to be widely used.
It is worth noting that the EXIF colour space recorded within
the EXIF information can only be one of two values, i.e. sRGB
or Uncalibrated. Generally digital camera manufacturers have set
their software to automatically write sRGB as the EXIF
colour space. This means that in the absence of an embedded colour
profile Photoshop 7 will attempt to open JPEG format digital camera
images into the sRGB colour space. If the EXIF colour space
has been set to Uncalibrated Photoshop will rightly assume that
the image has no predefined colour space information and the image will
not be colour managed (the image will be defined as Untagged RGB).
The screenshot shows the EXIF file for a JPEG image captured on
a Nikon D1X digital SLR camera. The owner had configured the camera
software to output the image in Adobe RGB and as we can see the
Nikon software has been very obliging and embedded the Adobe RGB
colour profile. Prior to Photoshop 7 this colour profile could not be
read and so the image would have opened with the "Missing Profile"
dialog flagging a potential problem - not anymore! The image will now
open directly into Photoshop or present the user with a "Profile
Mismatch" warning! Note: Each of these
terms will be discussed in Part 2 of this essay.
Also notice that the screenshot shows the EXIF colour space is
set for sRGB - so we have an image with two conflicting sets of
colour space information. Thankfully Adobe has coded Photoshop 7 to give
priority to the colour profile and when it's not present Photoshop will
use the EXIF colour space information.
Some Photoshop Revision!
Photoshop 7 continues to use document/image specific colour settings,
which means that the colour space of each document is independent of
others that may be open on the Photoshop desktop. As with Photoshop 6,
the working space defined in "Colour Settings" only has a bearing
on three types of image, viz.: -
existing images/documents without an embedded profile;
images/documents with no embedded ICC/ColorSync profile (i.e. "untagged
"Image specific" colour means that it's the profile embedded
within an image that determines how the image will be displayed (it's
appearance) and not the Photoshop working space. With Photoshop 7 we can
have multiple images, each in its own unique working space open at the
same time and each will be displayed accurately (of course this assumes a
well calibrated monitor).
Note that the "Assign Profile", "Convert to Profile" and
"Proof Setup" commands have undergone minor alteration. I will
discuss each of them in detail later.
Also note that except for the obvious difference in user interfaces;
Photoshop 7 for Mac OS9.x, Mac OSX and Windows share
a virtually identical feature set. Therefore the Windows based
screen shots that follow should be equally useful to Mac users.
Part 1 - Monitor
Calibration and Characterisation
On opening Photoshop 7 for the very first time we are presented
with an information dialog (shown below). The purpose of this dialog is
to warn the user that the Photoshop "Colour Settings" will be
automatically configured or to provide access for manual setup. As with
Photoshop 6 and unlike Photoshop 5 and 5.5 there is no "wizard" to
help the user through the process of configuring the "Colour Settings".
If Photoshop 6 is anything to go by many new users will panic at this
dialog and accept the defaults only to realise later that this was only a
For the purpose of this essay I to have chosen the "No" option
and have therefore accepted the default Photoshop settings. However, I
chose this option for no other reason than to concentrate upon monitor
calibration and characterisation. Once I have discussed calibrating the
monitor we can return to colour settings.
Accurately calibrating and characterising the monitor is a critical
element for any colour-managed workflow. Our aim is to calibrate the
monitor at system level so that we can eliminate unwanted colour casts
from the monitor, and so obtain the best possible display
environment for editing our images. We also need to characterise the
monitor by means of an ICC device profile. This profile is simply a file
that includes a description of the characteristics of your monitor. The
monitor profile will then be used by Photoshop to compensate for the
monitor's colour-display limitations. Photoshop optimises the display of
images using the image/document profile (e.g. Adobe RGB, sRGB,
ColorMatch), and the monitor profile.
Adobe no longer installs Adobe Gamma with the Mac version of
Photoshop, however, Mac OS9.x or OSX users can use the
Monitor Calibrator supplied as part of ColorSync or copy
Adobe Gamma from the Photoshop installation CD. The Monitor
Calibrator utility operates in a similar fashion to Adobe Gamma
and so I'll not bother describing it here.
To calibrate and characterise the monitor Windows users should
open the "Adobe Gamma" utility or a third party alternative. For
many new users Adobe Gamma is more than sufficient and it's free.
Adobe Gamma is a "Control Panel" utility that is
accessed from the "My Computer > Control Panel". Before running
Adobe Gamma, it is best that the monitor has been switched on for at
least 30 minutes. It is also best to work in subdued lighting when
calibrating a monitor using Adobe Gamma. Another good tip is to
set the "Desktop Colour" to grey.
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
Using the Load button choose your monitor profile or pick one
that's close. If in doubt choose the Adobe default monitor profile
or even sRGB, it really makes little difference since all we are
doing is defining the start point.
Before progressing to the next step, be sure to give the profile a
unique description and include the date (my example shows Mitsubishi
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.
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
Begin by keeping the "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
This is the step where we neutralise the colour imbalances inherent in
our monitor. Adjust each of the sliders in turn so as to blend the inner
square with its coloured 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.
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
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 slightly dimmer and more yellow white point.
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
because that most closely represents the environment in which it will
normally be viewed, you can set your Adjusted White Point to
5000oK, and Adobe Gamma will change the monitor display
accordingly: However, choosing this approach will all cause the graphics
card colour 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.
That's it, if all has gone well you will have adjusted the brightness,
contrast and colour 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
There are a number of third party alternatives to Adobe Gamma, which
can be purchased from companies such as Color Vision and Xrite
The advantage of Adobe Gamma (Windows systems) and Monitor
Calibrator (Mac systems) is that they're free, whereas the third
party products can cost nearly as much as Photoshop. However, since many
third party alternatives use "hardware" and not the "eyeball"
for measurement we are assured of greater accuracy.
Useful Information on location of
Windows 98, 98 Second Edition and Me - folder named windows/system/color
Windows 2000 and XP - sub-folder named system32/spool/drivers/color
Mac OS9.x - ColorSync profiles are located in the System
Folder/ColorSync Profiles folder
Mac OSX - ColorSync profiles are located in the
Part 2 - Photoshop 7
Now begins the process of configuring Photoshop. This is achieved
through the "Colour Settings" dialog found under the "Edit"
menu (Windows and Mac OS9.x) or the Photoshop menu (Mac OSX).
The "Colour Settings" dialog is the control room for the
Photoshop 7 colour management system, and like all control rooms it's
complicated. The default setting is "Web Graphics Default", but
this is certainly not the best choice.
I will work my way through each section of the "Colour Settings"
dialog in turn. Note the "Description" box at the bottom of the
dialog. 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 checkbox labelled "Advanced Mode", it's probably
best that you select it now. At least that way you will see everything
that the "Colour Settings" has to offer, even if some are only
applicable to the most advanced of Photoshop users.
first section is labelled "Settings"; this is simply a pop-up menu
with a list of pre-set Photoshop settings, plus any that you may have
saved. You need not worry too much about this section just yet.
If you are upgrading from Photoshop 6 it is simply a matter of
selecting the your previous setup. Notice that Adobe has retained the "Colour
Management Off" option for those users who find the whole subject
much too complicated. Although I don't recommend choosing this option I
am aware that quite a few new Photoshop users working on the PC Windows
platform find it easiest to handle.
The next section is labelled "Working Spaces", and as I
discussed earlier it will determine the working space of certain images
(namely the 3 types I mentioned in Part 1).
There are four types of working space in Photoshop, RGB,
CMYK, Grey and Spot. For the purposes of this exercise
I will concentrate mainly on the RGB colour space, since configuring the
others follow a similar process.
RGB - Working Space
Clicking the RGB pop-up menu with the mouse will produce a list of
options similar to that shown below. I chose "Adobe RGB (1998)"
because it's the working space I settled on when using Photoshop 5.
Notice that Adobe RGB (1998) appears within a group of four working
spaces, each of which is device-independent, and in common use with a
wide range of Photoshop users. Typically "sRGB" will be confined
to those users solely interested in web design, "ColorMatch" is a
favoured choice of many Mac users and "AppleRGB" is apparently for
Mac web design.
Notice that just above the four common working spaces we also find
options for "Monitor RGB" (green spot in the screenshot), and in
the case of Mac systems "ColorSync RGB". "Monitor RGB" is
simply the colour space of your monitor as created by the Adobe Gamma
utility (or a 3rd party software/hardware combination).
Unlike version 5 Photoshop 6 and 7 have no out-front way of informing
the user, which monitor profile is actually being used. However, 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. It is also possible to select your monitor
space as the Photoshop working space, but this is not really a good idea.
"ColorSync RGB" is only available to Mac users and will reflect
the settings chosen as part of the ColorSync setup.
The actual list of options available for selection as working spaces
differs depending on whether you activated Advanced Mode, or not.
If you chose to activate Advanced Mode then the list of available
RGB profiles will be quite extensive.
If you had previously been using another working space such as "BruceRGB"
then it should also appear as one of the options in this extended list.
If it doesn't you can still create it yourself by choosing "Custom"
(yellow spot in the above screenshot). The dialog below appears and you
simply type in the data as shown for the Primaries etc, remember
to give this new working space a name and click "OK".
CMYK - Working Space
Making your choice of CMYK working space isn't that different
to RGB except of the list of available colour profiles are rather
different. Again, having "Advanced Mode" activated gives us a more
extensive list. Since desktop inkjet printers from Epson, Canon and HP
actually require RGB data rather than CMYK and so configuring this
particular working space will have little or no influence in their actual
As mentioned above, the choice for you make is pretty much irrelevant
if using a consumer class inkjet printer. In my case I just picked US.
Web Coated (SWOP) V2. We can also have pick the old Photoshop 4
or 5 default CMYK options, the ColorSync settings (Mac only), or even
customise our own settings.
Greyscale - Working Space
With the Greyscale working space we have access to two gamma
settings, a series of five pre-set dot gain curves, the ColorSync "Grey
Work Space" (Mac only) and the ability to customise the dot gain to
our own requirements. This latter option is of particular significance to
Piezography Black and White printing system (discussed in a
separate essay). The screenshots below show the various options and a
typical customised "Dot Gain" curve.
Please note that if you choose to use a "Custom Gamma" or "Dot
Gain" this will be the working space listed in the Grey working space
A very important point regarding Greyscale is that it is not
tied to the CMYK setup! This is why some legacy greyscale documents might
not look quite the same as they did in Photoshop 5.x
Spot - Working Space
The Spot pop-up menu is broadly similar to the greyscale. The
options that we find include a series of five pre-set "dot gain"
options and the facility for customising the "dot gain" curve if
required. In my case I simply selected the standard 20% option.
Colour Management Policies was a new phrase introduced by Adobe
with Photoshop 6 and continues virtually unchanged in Photoshop 7. The
screenshot below shows a typical setup, but this hides a lot of important
This section is probably the one that will cause most new Photoshop
users the greatest difficulty and for that reason the explanation that I
give below will appear quite wordy, but don't be put off.
The area zoned in blue in the above screenshot is VERY
important and I highly recommend that you make the same choices for
Profile Mismatch and Missing Profiles as I have shown above. I
usually refer to these particular selections as my "safety net",
you'll see why shortly.
Basically each working space will have
the same set of three options, although we need not configure each
identically. These options are called Policies and include: -
In really simple terms, the "Off" Policy ensures that
Photoshop does as little as possible when dealing with profiles. In most
circumstances, it isn't a good choice and certainly not the choice to be
made by new users. The following will give you some idea as to the
default behaviour when this choice of policy is made.
Choosing "Off" will ensure that NEW images/documents
will (by default) be saved without an embedded profile.
On opening an image with an embedded profile that matches the
current working space, it will be retained and subsequently saved with
The default Pasting behaviour between images is to retain
numerical values (RGB pixel values), not the appearance. This means
that no conversion between colour spaces will take place.
Opening an existing image that has an embedded profile that does
not match the current working space (profile mismatch) will cause that
embedded profile to be stripped out of the file. The image will
subsequently be saved with no embedded profile. The following
warning dialog will appear if Ask When Opening has not been
activated for Profile Mismatches.
The problem with this configuration as compared to the one I
recommended in the "Blue Zone" above is that the user either accepts
what Photoshop dictates or doesn't open the image at all, not much of a
choice. To me this choice is akin to the novice high wire walker
operating without a "safety net", stay on the wire or fall off and break
their neck! There are always exceptions-to-the-rule and I will later
identify one that I find to be essential.
(b) Preserve Embedded Profiles
For most situations this is my preferred choice of colour management
policy since it offers the greatest degree of flexibility, assuming the
safety net mentioned above is in place. The following should give you an
idea as to the default behaviour of Photoshop when this choice of policy
Choosing "Preserve Embedded Profiles" will ensure that when
an image is opened into Photoshop and is found to have an embedded
profile that differs from the current Photoshop working space, then
that image and its associated profile will be left intact. By default,
Photoshop will make no attempt to convert the image to the current
working space; the original embedded profile will be retained and
subsequently saved with the image. Nevertheless, even though the image
and Photoshop are no longer in sync, colour space wise, the image
preview will be accurate.
When the image and the working space are matched Photoshop will
take no action; the image is opened and saved as normal.
The default behaviour when Pasting either an RGB or
Greyscale image is slightly more complex; whereby the appearance of
the pasted image will be preserved but the numbers will change (the
pixel values will change). In the case of CMYK it is the numbers that
will be retained, not the appearance.
If the image being opened or imported has no embedded profile then
Photoshop will use the current working space for editing and
previewing purposes, however, the profile will NOT be embedded
into the image when it is subsequently saved.
Creating a new document with this policy setting will mean that
the current working space is used for editing, previewing and the
associated profile will eventually be embedded into the file when
The following dialog will appear if Ask When Opening has not
been activated for Profile Mismatches. Again, my earlier comment
about Photoshop imposing its will on proceedings applies.
At first glance the above dialog appears virtually identical to that
shown for the OFF Policy, but there is a subtle difference
- the profile is retained rather than discarded.
(c) Convert to Working Space
This policy behaves in an almost identical fashion to 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.
By default, if an image with no embedded profile is opened or
imported into Photoshop then the current working space will be used for
editing and previewing, however, upon saving the image no profile will
be embedded. Photoshop will denote the image colour space as "Untagged
If an image is opened or imported and has an embedded 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. Newly created images will be
edited, previewed and ultimately saved in the current working space.
Finally, the default pasting behaviour is to convert and thus
preserve the appearance of the image. 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.
Overriding the Default Policy Behaviour
The previous section described how our choice of Colour Management
Policy determined the default behaviour of Photoshop 7 under various
scenarios. However, we need not be confined to these pre-set outcomes. At
the beginning of the previous section I recommended that each of the "checkboxes"
for Profile Mismatches and Missing Profiles be set for
Ask When Opening or Ask When Pasting as appropriate. It is
only through setting these checkboxes to "ON" that we can enable
the default behaviour override facility. Furthermore, it is only by
setting these checkboxes to "ON" that we can activate the "safety
Basically the three checkboxes have the following impact on the
Colour Management Policies: -
(i) Profile Mismatches: Ask When Opening
Photoshop has been set to present the user with a dialog box when the
image being opened or imported has an embedded profile that does NOT
match the current working space. The dialog box looks like the following
and contains three options; the pre-set selection is dependent upon the
Colour Management Policy in operation at the time. Noticed that
all the necessary information required to make an informed decision is
The above example is pre-set for how the dialog would appear when the
Colour Management Policy is set for Preserve Embedded Profile.
The user may now choose to leave the image as is, allow the conversion
or strip out the embedded profile and switch off colour management. Had
the policy been Convert to Working Space the dialog would
have looked almost identical except that it would have been pre-set for
"Convert document's colors to working space".
I think you will agree that the above dialog is a lot more user
friendly than the one that appeared under similar circumstances when
Ask When Opening was "unchecked". At least we now have the
opportunity to assign an alternative profile to the image before it
Now that Photoshop can read the EXIF colour space information
it's likely that many digital camera users will be seeing this
particular dialog on a regular basis. Since no benefit will be gained
by converting the image the best choice in such circumstances is to
leave the default "Use the Embedded Profile" rather
than be temped to choose "Convert document's colours to working
Users of cameras such as the Canon EOS 1D and Nikon D1X/H may have
programmed the camera to process the images into the Adobe RGB (1998)
colour space and will therefore know that the above warning is
incorrect. In such circumstances they should choose to either accept
the embedded profile or discard it, but they must then use the
Assign Profile command to assign the correct profile. Both
methods are equally valid. Remember Assign Profile does NOT
change the image file only its appearance. Assign Profile and
Convert to Profile are discussed on page 8.
If you have a custom profile for your digital camera you
should follow the same workflow described for the 1D and D1X/H, but
substitute your custom profile in for Adobe RGB (1998).
(ii) Missing Profiles: Ask When Opening
Photoshop has been set to present the user with a dialog box when the
image being opened has no embedded profile. The dialog box looks similar
to the following and again contains three options; the pre-set selection
is dependent upon the Colour Management Policy in operation at
The above example is pre-set for how the dialog would appear when the
Colour 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 colour space and you want the image to appear 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 EXIF colour space information. Note that the source
profile MUST be known and available to the user before this
option can be selected.
(iii) Paste Profile Mismatches: Ask When
The screenshot below shows the "Paste Profile Mismatch" dialog
that will appear in the event of the colour spaces of the two images not
Note that the terms preserve "colour appearance" and "colour
numbers" relate to the source image, not the destination.
The various dialogs that have been shown above are only a sample of
those that may appear as you open or import images that contravene the
defined Colour 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
This section will only be present in the Colour Settings
dialog if the user chooses to activate the Advanced "checkbox".
The screen grab below shows this section of the Colour Settings
dialog in its default configuration.
Engine: this is the name of the engine, which will be used for
all colour 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 the default 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
With Relative Colorimetric it is only those source colours
that are out of gamut (i.e. can't be viewed/printed accurately within
the destination colour space) that will be mapped to the closest
in-gamut colour, the remainder are left unchanged. This means that in
the case of images with lots of out-of-gamut colours the visual
relationship between the colours (after conversion) will almost
certainly change. With Perceptual, all colours of the source
colour space will be mapped to the nearest in-gamut colour of the
destination colour space thus maintaining the visual relationship
between colours. In other words, with Perceptual the whole image
colour gamut will be compressed so that it fits within the new colour
space. The Photoshop default and recommendation is Relative
Colorimetric and after considerable experimentation I have decided
to go with Adobes recommendation.
Use Black Point Compensation: this should be kept "checked".
Black Point Compensation ensures that the darkest neutrals of the
source colour space are mapped to the darkest neutrals of the
destination colour space. In most circumstances toggling BPC
ON and OFF will result in no obvious change to the image
Use Dither (8-bit/channel images): as with Black Point
Compensation this should be kept "checked". The description
box at the bottom of the Colour Settings dialog box will give you
some clue as to what it does.
As with the Conversion options, this section will only be
present in the Colour Settings dialog if the user chooses to
activate the Advanced "checkbox". The screenshot below
shows this section of the Colour Settings dialog in its default
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 colour spaces may
find it useful, however, the majority of Photoshop users should
leave it "Off".
Saving Out Your Own Default Colour 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.
The screen grab below shows my own Colour Settings
configuration. Notice that I have chosen Off for my Greyscale Policy
and use a customised dot gain for the greyscale working space, you
shouldn't try to repeat these settings since they are specific to my
Piezography BW workflow.
Customised Colour Settings
Part 4 - Managing
Image/Document Colour Space
On the Colour Space conversion and profile embedding front we
find that little has changed from Photoshop 6. Without the tools that
follow it would be virtually impossible for the user to maintain a fully
As with Photoshop 6 the Assign Profile command is accessed via
the Image > Mode menu and allows the user to assign any profile of
their choosing to an image. The command itself was designed for only a
few limited uses, typically with images that have been scanned into
Photoshop using a Twain module or a scanner package that has no means of
embedding an ICC/ColorSync profile. It will also be useful
handling images from digital cameras that have no embedded profile or
incorrect EXIF colour space information.
Assuming that the colour management policy is not off, then an image
imported into Photoshop with NO embedded profile will be "assigned",
"previewed" and subsequently "saved" in the
current Photoshop working space. Obviously, this may not be the most
appropriate colour space in which to edit or save the image, so assuming
the user has the correct source profile we can make the necessary
It is important to note that unlike the Profile to Profile command of
Photoshop 5, assigning a profile will NOT convert the image (will
not change the numbers; i.e. RGB pixel values). It simply tells Photoshop
the actual colour space that you wish to edit and view the image in (it
changes the image appearance or meaning of the numbers).
Other potential uses for Assign Profile include the removal of
an embedded profile (i.e. don't colour manage the image). The example
screenshot shows a case where I chose to assign a customised profile for
my digital camera to an image.
Convert to Profile
The Convert to Profile command found under the Image > Mode
menu is basically an enhanced version of the Photoshop 5
Profile-to-Profile. With Profile-to-Profile we were able to
define the source colour space (and probably get it wrong), in Photoshop
6 and 7 this cannot be done since the assigned profile for the image is
locked. The only way that this source profile can be changed is via the
Assign Profile command discussed above.
In the example above I show an image with an embedded profile (Source
Space = Canon EOS D30 ..........NSC) being converted to Adobe RGB
(1998) (i.e. the Destination Space). Whenever we make this
conversion it will be the profile for the destination space that is
embedded within the image file when saved. Convert to Profile
changes the numbers (i.e. pixel values). The inclusion of 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, use it to your benefit.
Notice that the Intent is set to Relative Colorimetric
as this was the default Intent chosen by me when configuring the
Colour Settings. However, as with many Photoshop setting the
Intent is "sticky", which means that if I had chosen
Perceptual instead then the next time I chose Convert to Profile
the Intent would be set to Perceptual. The moral being -
always check the actual value before clicking OK.
The Profile-to-Profile method of printing
an image in Photoshop 5.x, here's its equivalent!
Actually, some users prefer to use the Convert to
Profile command to prepare their images for printing, much as they
did with Profile-to-Profile in Photoshop 5. The advantage
of this approach is that it provides a very accurate preview of how the
image will print, and gives the user the ability to use (and preview) the
alternative conversion options.
If you do choose this approach for printing then simply
select Same as Source (direct equivalent of RGB in Photoshop 5) as
the Print Space, the remainder of the settings are as described
Printer Colour Management tutorial. Of course, the printer driver
must be set for No Color Adjustment mode.
Photoshop Print dialog settings
required for this method of printing
Also, notice that whereas in the previous examples the
Source Space was the same as the Photoshop Working Space it is
now the name of the media profile you selected in Convert to Profile
(e.g. Epson 1270 Premium Glossy Printer Profile).
Last but not least, the new Save As dialog throws up a host of
useful features. The Embed Profile checkbox is very important and
will reflect your choice of Colour Management Policy. You switch
it ON or turn it OFF as you please. The latter option being
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
2000 system; the Mac versions will look slightly different,
but are functionally identical.
The other save options present in the dialog are those associated with
Layers, Alpha Channels, Annotations, etc. Again, we
can choose to uncheck them and so save the image without the layers, etc.
Note that the Save As a Copy feature is engaged by default as soon
as you uncheck Layers; this prevents you trashing a lot of hard
Hopefully the material presented in this essay has been
helpful and improved your understanding of Photoshop's approach to
managing colour. As noted throughout the essay there is vast body of
material to be found all over the internet.