Choosing A Color Mode; Color Modes And Models - Adobe PHOTOSHOP 5.0 User Manual

Chapter 4: Choosing a Color Mode
F
amiliarity with color theory and termi-
nology can help you understand how color
is measured and how Adobe Photoshop
uses this information to define, display, and print
color values.

Color modes and models

A color mode in Photoshop determines the color
model used to display and print Photoshop
documents. Photoshop bases its color modes on
established models for describing and reproducing
color. Common models include HSB (for hue,
saturation, brightness); RGB (for red, green, blue);
CMYK (for cyan, magenta, yellow, black); and
CIE L*a*b. Photoshop also includes modes for
specialized color output such as indexed color
and duotones.
HSB model
Based on the human perception of color, the HSB
model describes three fundamental characteristics
of color:
Hue is the color reflected from or transmitted
•
through an object. It is measured as a location on
the standard color wheel, expressed as a degree
between 0 and 360 . In common use, hue is
identified by the name of the color such as red,
orange, or green.
Saturation, sometimes called chroma, is the
•
strength or purity of the color. Saturation repre-
sents the amount of gray in proportion to the hue,
measured as a percentage from 0% (gray) to 100%
(fully saturated). On the standard color wheel,
saturation increases from the center to the edge.
Brightness is the relative lightness or darkness of
•
the color, usually measured as a percentage from
0% (black) to 100% (white).
Although you can use the HSB model in
Photoshop to define a color in the Color palette or
Color Picker dialog box, there is no HSB mode
available for creating and editing images.
For a color illustration of the HSB model,
see figure 4-1 on page 223.
RGB model
A large percentage of the visible spectrum can be
represented by mixing red, green, and blue (RGB)
colored light in various proportions and inten-
sities. Where the colors overlap, they create cyan,
magenta, and yellow.
Because the RGB colors combine to create white,
they are also called additive colors. Adding all
colors together creates white—that is, all light is
reflected back to the eye. Additive colors are used
for lighting, video, and monitors. Your monitor,
for example, creates color by emitting light
through red, green, and blue phosphors.
For a color illustration of additive colors in
RGB, see figure 4-2 on page 223.
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