What is Color Management?
Color management is the practical application of the
science of color perception and reproduction to make it
possible to predict and previsualize how colors will be
reproduced using differing mediums such as fabric and
photographic dyes, CRT and LCD computer screens, and various
types of printing.
Human perception of color is highly subjective and
changes depending on the viewing conditions. Color
management quantifies color using a device called a
photospectrometer, which can record the intensity of each
wavelength (i.e., color) of light. Using this tool color
scientists have create a "roadmap" for color which can be
used as a tool for standardization and communication of
color information between devices.
Imagine for a moment you are the marketing
department of a clothing line which is launching a new line
of clothes featuring this season's popular color, pastel
purple. You'd want the customer to see that color accurately
regardless of whether they viewed the product on television,
the Internet, a glossy magazine, or a newspaper. How can
this possibly be accomplished? By knowing in advance how
each reproduction method wlll alter the appearance of the
color, and then altering the color values in the file to
compensate for the differences.
Throughout the reproduction process an image may
pass through many hands and be viewed on many computer
screens and proofs. If a photographer "tweeks" the photo so
it looks good on his monitor, then sends it to a designer
who changes it to suit his different viewing conditions,
then sends it to a printing company who alter it yet again
to compensate for dot gain and other things that occurs on
press, there may be so much manipulation of the image data
that the original color information and image detail is
Why does a digital photographer need to know about it?
The CCD sensors in a consumer level (8
bit-per-color) digital camera can only record 256 levels
each of red, green, and blue (RGB) luminance. These values
are the same when the file is opened on any computer, but
the photograph will look different depending on the
intensity and constast of the monitor it is viewed on.
Take the color "white" for example. In a camera file
pure white is recorded as the maximum values (255) of red,
green, and blue (i.e. 255/255/255). On a computer screen
the intensity of the red, green, and blue phosphors can be
adjusted individually o make this "pure" white value of the
appear almost any color. Color management tools now included
with all computer systems allow the user to calibrate the
"white point" of the monitor, measured in degrees Kelvin,
and contrast, measured as "gamma" to one of several industry
standards. This will ensure that the appearance of a file
edited on the photographer's computer will be the same on
other computers when the file is downloaded via the Internet or
viewed from a disk.
When digital camera files are printed, with the RGB
data values used by the camera and monitor are converted to the Cyan,
Yellow, Magenta, and Black (CYMK) colors of printing inks.
How the image will look after this color conversion process
takes place depends on the purity of the inks, the color of
the paper, and most significantly the light under which the
printed image is viewed. A print viewed under tungten light
will differ from one viewed under natual light, and how it
appears under natural sunlight will vary depending on the
time of day.
When color management is used the translation RGB
color data to CYMK is done via conversion tables called ICC
profiles. Tables for monitor and printer/ink/paper
combinations are created by displaying a standard color
target with known color values and measuring how it is
reproduced. It now possible to "soft proof" a color subject
in PhotoShop version 6.0 by viewing an on-screen simulation
of how it will print created from the printer ICC profile.
Understanding color management and how PhotoShop uses it
will give a digital photographer more creative control over
the medium. It will help ensure the colors and contrast edited by
the photographer on his screen appear the same on others. If the
photos are printed it will ensure the color and contrast on the
printed page is as close to the screen image as possible.
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