Adobe PHOTOSHOP 5.0 User Manual page 348

340 CHAPTER 15
Printing
Because duotones use different color inks to
reproduce different gray levels, they are treated in
Photoshop as single-channel, 8-bit, grayscale
images. In Duotone mode, you do not have direct
access to the individual image channels (as in RGB,
CMYK, and Lab modes). Instead, you manipulate
the channels through the curves in the Duotone
Options dialog box.
To convert an image to duotone:
Convert the image to a grayscale image by
1
choosing Image > Mode > Grayscale. Only 8-bit
grayscale images can be converted to duotones.
Choose Image > Mode > Duotone.
2
Select Preview to view the effects of the duotone
3
settings on the image.
Specify the type of image, the ink colors, the
4
duotone curves, and the overprint colors for the
duotone image. These options are described in the
following sections.
Click OK.
5
To apply a duotone effect to only part of an
image, convert the duotone image to
Multichannel mode—this converts the duotone
curves to spot channels. You can then erase part
of the spot channel for areas that you want
printed as standard grayscale. (See "Using spot
channels" on page 245.)
Specifying the duotone type and ink
colors
The duotone type—monotone, duotone, tritone,
or quadtone—determines how many ink controls
are active.
For a color illustration of duotones, see
figure on page 236.
To produce fully saturated colors, print darker inks
before lighter inks. The order of inks in the
duotone dialog boxes affects how Photoshop
applies screens, so make sure that inks are specified
in descending order—darkest at the top, lightest at
the bottom.
To specify the duotone type and its ink color:
In the Duotone Options dialog box, for Type
1
specify monotone, duotone, tritone, or quadtone.
Click the color box (the solid square) for an ink.
2
Use the color picker or the Custom Colors
3
dialog box to select the ink you want. When you
close the dialog box, the ink color appears in the
color box and the color name in the text box. (See
"Using the Adobe Photoshop Color Picker" on
page 218.)
If the ink is to be separated on a process color
4
plate, name it "cyan," "magenta," "yellow," or
"black."
Modifying the duotone curve
A separate duotone curve specifies how each ink is
distributed across the shadow and highlight areas
of the image. This curve maps each grayscale value
on the original image to the actual ink percentage
that will be used when the image is printed. A
diagonal curve indicates equal values and even
distribution of ink.