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- Display profiles for CRT and LCD flat panel displays. To profile a display,
you attach a color measuring device called a spectrophotometer or colorim-
eter to the display screen. Profiling software then flashes a number of known
colors on the display while the device reads each colors’ values. The differ-
ences between the known and measured results are stored in the display’s
profile. Some color management systems let you create a display profile visu-
ally without using an expensive color measuring device. This software walks
you through adjusting brightness, contrast, and color balance as you create
the profile step by step. Although not as accurate as a profile done with an
instrument, it’s better than nothing. - Output profiles for devices such as printers and projectors. To profile
a printer, you open an image of a color chart with known color values and
print it out. You then use a spectrophotometer to read each color patch in the
printout. Profiling software compares the known and printed values for each
patch and stores the differences in the device’s profile.
When you buy a printer, it often comes with a number of profiles created
by the manufacturer for various papers. Since these profiles are generic, the
ones you create for your specific printer will be more accurate but you have
to create a profile for every ink/paper combination you use. Although incon-
venient, you have to do this to get the best possible results on your specific
printer and whenever you use paper or ink from a third-party.
To simplify the use of profiles, the International Color Consortium (ICC) has
defined a widely accepted format for them so they can all work together. This
makes it possible to move images with embedded ICC profiles (called tagged
images) between different applications, hardware, and even operating sys-
tems while retaining color fidelity. If an ICC profile isn’t assigned to an image,
you can use an application such as Photoshop to assign one.
One interesting use of profiles is in a process called soft proofing. The pur-
pose of this proofing is to show on the screen what your image will look like
when printed on a specific type of paper. When you soft proof, the program
uses the printer’s profile, normally used as an output profile, as the input
profile. When paired with the display’s output profile, you get a close approxi-
mation on the display of what the printed image will look like.
Color mAnAging—uSing ProFileS
When you are ready to pass an image between two devices, you need both an
input and output profile. A single profile describes a device but doesn’t affect
it. The various profiles that can be paired up include the following:- The image or input profile is embedded in the image by the camera, or
you can embed one using a photo-editing application. Many photo-editing
applications also let you select a working space profile, which is then paired
with the display profile. - The display profile can be changed using an operating system dialog box.
- The output profile, often specific to a paper, is specified at the time you
print using your photo-editing application’s print dialog box.
Once you have specified a pair of profiles, the color management system
works as follows:
- It looks up each color value in the image in the input profile and adjusts it
as specified in that profile. - It looks up the adjusted color in a Color Matching Method (CMM) that
TiP
Profiles are not
permanent. they
need to be redone
periodically because
hardware colors drift
as a device ages.
they also need to
be redone if any
settings or parts are
changed.Sony’s Artisan Color
Reference System has
integrated profiling
hardware and software.
ColorVision’s PrintFix
has a target that you
open on your computer
and print out. You then
scan the printout and
the printed colors are
compared to the known
colors in the target. The
differences are stored in
the new printer profile.
Color mAnAgement—the workFlow