Technical data

Color and Input/Output Options 95
RGB mode is much less intuitive than HSL as a method of mixing
colors, but it’s the standard way of describing colors the way they’re
displayed on computer monitors—as mixtures of separate Red, Green,
and Blue components. Anyone who’s seen (in a museum, perhaps) a
demonstration of three projector beams in a dark room, one of each
color, merging to produce a pool of white light, has seen a primitive
version of the RGB system. Turn all the elements off and you get black.
On computers, as with the HSL system, 8 bits are used to encode each
of the three channels, for a total of 24 bits, and with 256 possible levels
(0-255) for each channel. An RGB value of “0,0,0” represents pure
black, while a value of “255,255,255” represents pure white.
To quickly get a feel for the HSL and RGB color mode variables,
double-click either the foreground or background color swatch on the
Color tab and try mixing your own colors using the Adjust Color
dialog. (See online help for details.)
Finally, CMYK is a color model used for preparing printed work,
where ink on paper is the medium that determines color reproduction.
It’s based on the “subtractive” principle by which our perception of a
pigment’s color depends on the light wavelengths it absorbs and
reflects. Traditional process color printing creates colors by mixing inks
and absorbing light, so that your eyes can mix the reflected light.
The four process inks are Cyan, Magenta, Yellow, and Black (Black is
referred to as Key). Mix the four process inks, and you get black. No
ink gives you white (or the color of the paper). In PhotoPlus, the C, M,
Y, and K channel values are given as percentages, from 0 to 100%.
PhotoPlus supports CMYK output of process color separations (see the
section later in this chapter).
Color mode tips
♦ The color mode setting (on the Color tab) determines how image
data gets pasted from the Windows Clipboard—in other words, as
grayscale values in Grayscale mode, or as full 24-bit color in any of
the other modes.
♦ If you start editing a layer mask (which represents opacity values
by shades of gray), the Color tab switches temporarily to Grayscale
mode. Applying the Image/Adjust/Grayscale filter, however,
doesn’t affect the color mode.