The previous section
concentrated upon how we see colour on the monitor and how
accurate that representation of colour actually is. The "Color
Settings" menu option found under the "File"
menu is where we effectively tell "Photoshop"
what red, green, blue, cyan, magenta and yellow actually look
like, and how we want the colour management system therein to
operate on these colours.
(i) RGB Setup
The RGB setup dialog is
where we define the Photoshop RGB "Work Space".
Just to confuse matters it’s also known the "Editing
Space", or "Colour Space", I'll be
using the three terms interchangeably.
The work space selected
here is normally considered "device independent"
(i.e. independent of scanner, monitor or printer devices), and
allows Photoshop to attach a specific colour meaning to our RGB
Remember also that
unless you specify otherwise the RGB work space (profile)
selected by you here is the profile that will be saved with your
file (i.e.; "tagged").
Before we begin
selecting our preferred RGB work space I will dispel a commonly
held misconception, namely that the gamma and white point
selected for the RGB work space must be the same as we have
chosen when calibrating our monitor, wrong!, simply because the
two are NOT related. There is absolutely no reason why
you should keep both compatible.
There are nine "Canned"
RGB colour spaces supplied as standard with Photoshop 5, each of
which is based upon industry standards. There is also the option
to select your "monitor space" (i.e. Monitor
RGB) or define your own "Customised" RGB work
The selection of Monitor
RGB is not recommended since it is not "device
independent", but most importantly, monitors cannot
display a considerable part of the gamut of CMYK output devices
such as our inkjet printers.
Of the nine "canned"
RGB colour spaces there are only three that are truly useful to
most of us printing to inkjet printers, namely:
- Adobe RGB (1998)
– based upon a gamma of 2.2 and a White Point of 6500K,
which is broadly compatible with daylight in shade. This
colour space comes very close to encompassing the entire CMYK
gamut, although it has some difficulty with greens. Its
gamma value of 2.2 ensures adequate separation of shadow
detail is maintained.
- ColorMatch RGB
– this RGB colour space is based upon a gamma of 1.8 and a
White Point of 5000K. It is also widely used by Mac users,
and has slightly narrower colour gamut than Adobe RGB. Its
main drawback relates to the gamma value of 1.8, which can
cause some posterisation problems in shadow areas. That said
it is still a perfectly acceptable workspace on either the PC
or Mac platforms.
With the "Custom"
option we can define our own RGB colour space, although this
doesn’t come highly recommended. That said there is one custom
colour space that has almost become an industry standard, i.e.
"BruceRGB". The specification for this work
space is as follows:-
- sRGB – this
RGB colour space is similar to Adobe RGB above in that it is
based upon a gamma of 2.2 and a White Point of 6500K.
However, the colour gamut of this space is somewhat limited
and can only be recommended for use with the 4-colour range
of inkjet printers from Epson, Canon, HP, etc. It is also
widely used for web pages, etc.
This colour space has all
the advantages of Adobe RGB (1998) but doesn’t suffer the
problems associated with greens to the same extent. This colour
space is now highly favored by users of the 6-colour consumer
inkjet printers such as those supplied by Epson.
Point = 6500K
Primary xy = 0.6400, 0.3300
Primary xy = 0.2800, 0.6500
Primary xy = 0.1500, 0.0600
Remember to use the
"Save" button after you create this profile
(this will ensure that it is retained for future use). You can
give the profile any name you like, although I recommend
BruceRGB, especially if you propose to share your files with
others, since there’s a greater chance that they will be able
to handle your file without conversion.
The last setting that
you can make in the RGB setup dialog is – "Display
Using Monitor Compensation" (DUMC). With this
feature activated we are instructing Photoshop to carry out an
"on-the-fly" conversion of the image data from
our selected RGB "work space" to our "monitor
space", using the information contained in your
customised monitor profile. So now we see why it is so essential
that the monitor be calibrated correctly. It should also be
noted that this "on-the-fly" conversion does
not impact upon, or damage the image data in any way.
If you find that your prints don't match the monitor
image (i.e. to dark, to light, etc.) then try switching DUMC
off. If the screen more closely matches the print with DUMC
off then your monitor calibration is "broken". I
recommend that you try the method I described for monitor
calibration which is based upon the "Adobe Monitor
For Photoshop users who
share files with others, and especially across platforms (PC to
MAC and vice versa) the following should be noted:
"If you open a
file that has been colour adjusted in a gamma 1.8 workspace
into a gamma 2.2 workspace without conversion the resulting on
screen image will appear darker and more contrasty than it
would have otherwise have done. Conversely, if you originally
colour corrected a file in a gamma 2.2 workspace and then open
it in gamma 1.8 workspace without conversion then the image
will appear flat and light."
The moral here is that
unless you have very good reasons stopping you converting to
your own workspace then you should always allow the colour space
conversion to take place.
(ii) CMYK Setup
For the most part this
dialog is of no interest to those of us who concentrate solely
on an RGB workflow. That said there is one "gem"
buried within the CMYK settings dialog that anyone using "Custom"
printer profiles simply must take heed of, i.e. "soft
proofing" your RGB printer. Unfortunately, it doesn’t
appear to work too well with Epson’s new "Standard"
Soft proofing your RGB
printer is based upon a very complex procedure developed by Mark
Hamburg of Adobe, my thanks to Andrew Rodney for giving us
access to the Photoshop Actions that make the whole process much
simpler to implement.
So, rather than try to
explain it myself I’ll let Andrew Rodney do it for me: -
5 has no RGB soft proof (unlike the CMYK Preview/Soft Proof
feature). That means that while having a calibrated display
is VERY important, you are not looking at your RGB file with
an output simulation. There IS a way to trick Photoshop into
providing a soft proof for RGB files and you will generally
see a much closer screen to print match. This is mostly
affecting out of gamut (very saturated) colours. The process
of converting an RGB output file into a CMYK profile for
soft proofing is long and complex. However, you can find a
PDF with the recipe and a Photoshop action on my Web page:-
allows you to load into the CMYK setup, a modified RGB
profile for your printer and then use the CMYK preview (Ctrl+Y)
to redraw the screen to get a closer match. Of course the
quality of all this depends on the quality of the output
profile and how well your display really is profiled and
(iii) Grayscale Setup
This dialog allows us to
define our grayscale working space by stating whether it is
based on RGB neutral values (i.e. equal values of Red, Green and
Blue) or simply based on Black ink. If the latter is chosen then
the dot gain curves defined in the CMYK dialog are used.
Remember to switch "Off" RGB soft proofing
feature described above if you are using that feature.
If you are using a
"Custom" printer profile there is a lot of
merit in converting your grayscale images back to RGB before
outputting to the printer. Although, it is worth trying both
options, and settling one you prefer rather than blindly
following convention or even my suggestions.
(iv) Profile Setup
I’ve heard it said
that unless you share your image files with other users or have
been using an earlier version of Photoshop then the Profile
Setup feature is surplus to requirements, nothing could be
further from the truth.
The Profile Setup dialog
is in fact fundamental to determining how (or even whether)
Photoshop acts upon images when they are "opened"
or "saved". If you set the various options
incorrectly you could potentially destroy an image and never
even know that you’ve done so.
It performs two
> It offers you a
method of ensuring that images get converted into your
working space, and
As can be seen from the
screen-grab below, the dialog is separated into three distinct
sections, "Embed Profiles", "Assumed
Profiles", and "Profile Mismatch Handling".
> It lets you embed an
ICC profile (or "tag") within the file that
describes the workspace in which the image was created.
The Embed profiles
section is fairly straightforward in that by checking the boxes
we are effectively telling Photoshop to automatically embed our
workspace profile within the file when we save the image. By
default all the checkboxes are normally "On".
It is recommended that you leave this section of the Profile
Setup in its default state, the exception being when you open a
printer calibration Test target (typically those used with
Device Profiling Packages such as WiziWYG, EZcolor, etc.). With calibration targets it essential that you
don’t allow the image to be saved (usually by accident) with
your work space profile, so its better to be safe than sorry,
with printer calibration images make sure "Embed
Profiles" is "Off". However, remember
to set it to "On" again once you finish with
the printer calibration.