Datasheet

Working with Digital Images

Multichannel mode. Multichannel mode uses only spot channels (see Figure 1.16), chan-

nels that store parts of an image that you want to print in custom-selected inks (sometimes

called spot colors), such as inks from the Pantone color library. In Multichannel mode,

you can put certain parts of an image on each spot channel and assign custom-selected

inks to the spot channel.

For example, you can put a custom-red-ink logo on the spot channel for red ink and a

custom-blue-ink background on the spot channel for blue ink. You can also put image

areas that you want to print in clear varnishes on spot channels.

Spot channels result in inks overprinting each other, so if the logo mentioned previously

is to print in red ink only, then the area corresponding to the logo in the blue spot chan-

nel must contain no pixels in order to avoid blue ink printing on the red ink logo.

FIGURE 1.16

Multichannel mode spot color channels in a two-color image

NOTE

Spot channels can be added to CMYK images by using the Channel palette menu.

A common scenario would be adding a spot channel for a clear varnish to a CMYK

image.

Color space

There are many colors that can be formed from combinations of the basic sets of colors that make

up each color mode, such as RGB (Red, Green, Blue) or CMYK (Cyan, Magenta, Yellow, Black).

But not all devices (monitors, presses, desktop printers) can reproduce all the possible color com-

binations within each color mode. Therefore, there are sets of color-combinations within each

color mode that are customized for different devices and that you can use to make up the colors in

your images. You can think of these sets of color-combinations as color palettes. They also can be

referred to as color spaces, color gamuts, or color profiles.

When you use a set of color-combinations that is specially made for an image’s destination device,

your image should look better when it is reproduced that device. For example, if you erroneously

use a color space that is made for uncoated paper for an image that is going to be printed on glossy

paper on a printing press, you are allowing your image to potentially have many more colors than

can be reproduced satisfactorily on uncoated paper. There can be unpredictable results in this situ-

ation. It’s better in this situation to use a color space that is specifically tailored to uncoated paper

printed on a printing press.