Adobe 13101332 - Photoshop - Mac, Руководство пользователя

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Using Help | Contents | Index Back 88
Adobe Photoshop Help Working with Color
Using Help | Contents | Index Back 88
Although RGB is a standard color model, the exact range of colors represented can vary,
depending on the application or display device. Photoshop’s RGB mode varies according
to the working space setting that you have specified in the Color Settings dialog box.
(See
“About working spaces” on page 106 .)
CMYK model
The CMYK model is based on the light-absorbing quality of ink printed on paper. As white
light strikes translucent inks, certain visible wavelengths are absorbed while others are
reflected back to your eyes.
In theory, pure cyan (C), magenta (M), and yellow (Y) pigments should combine to absorb
all light and produce black. For this reason these colors are called
subtractive colors.
Because all printing inks contain some impurities, these three inks actually produce a
muddy brown and must be combined with black (K) ink to produce a true black. (
K is used
instead of B to avoid confusion with blue.) Combining these inks to reproduce color is
called
four-color process printing .
The subtractive (CMY) and additive (RGB) colors are complementary colors . Each pair of
subtractive colors creates an additive color, and vice versa.
Subtractive colors (CMYK)
CMYK mode
In Photoshop’s CMYK mode, each pixel is assigned a percentage value for each of the
process inks. The lightest (highlight) colors are assigned small percentages of process ink
colors, the darker (shadow) colors higher percentages. For example, a bright red might
contain 2% cyan, 93% magenta, 90% yellow, and 0% black. In CMYK images, pure white is
generated when all four components have values of 0%.
Use the CMYK mode when preparing an image to be printed using process colors.
Converting an RGB image into CMYK creates a
color separation . If you start with an RGB
image, it’s best to edit first and then convert to CMYK. In RGB mode, you can use the Proof
Setup commands to simulate the effects of a CMYK conversion without changing the
actual image data. (See
“Soft-proofing colors” on page 113 .) You can also use CMYK mode
to work directly with CMYK images scanned or imported from high-end systems.
Although CMYK is a standard color model, the exact range of colors represented can vary,
depending on the press and printing conditions. Photoshop’s CMYK mode varies
according to the working space setting that you have specified in the Color Settings
dialog box. (See
“About working spaces” on page 106 .)