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. A simple search using "google.com"
and the keys words "color management" is all that is required.