Printing Duotones; To Create A Trap; About Duotones; To Convert An Image To Duotone - Adobe PHOTOSHOP CS2 User Manual

Trapping is intended to correct the misalignment of solid colors. In general, you don't need traps for continuous-tone
images such as photographs. Excessive trapping may produce an outline effect. These problems may not be visible
on-screen and might show up only in print. Photoshop uses standard rules for trapping:
All colors spread under black.
•
• Lighter colors spread under darker colors.
Yellow spreads under cyan, magenta, and black.
•
• Pure cyan and pure magenta spread under each other equally.

To create a trap

1 Save a version of the file in RGB mode, in case you want to reconvert the image later. Then choose Image > Mode >
CMYK Color to convert the image to CMYK mode.
Choose Image > Trap.
2
For Width, enter the trapping value provided by your print shop. Then select a unit of measurement, and click OK.
3
Consult your print shop to determine how much misregistration to expect.

Printing duotones

About duotones

You can create monotones, duotones, tritones, and quadtones in Photoshop. Monotones are grayscale images printed
with a single, nonblack ink. Duotones, tritones, and quadtones are grayscale images printed with two, three, and four
inks. In these images, colored inks, rather than different shades of gray, are used to reproduce tinted grays. For the
purposes of this discussion, duotone refers to monotones, tritones, and quadtones as well as duotones.
Duotones increase the tonal range of a grayscale image. Although a grayscale reproduction can display up to 256
levels of gray, a printing press can reproduce only about 50 levels of gray per ink. For this reason, a grayscale image
printed with only black ink can look significantly coarser than the same image printed with two, three, or four inks,
each individual ink reproducing up to 50 levels of gray.
Sometimes duotones are printed using a black ink and a gray ink—the black for shadows and the gray for midtones
and highlights. More frequently, duotones are printed using a colored ink for the highlight color. This technique
produces an image with a slight tint and significantly increases the dynamic range of the image. Duotones are ideal
for two-color print jobs with a spot color (such as a PANTONE Color) used for accent.
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 grayscale by choosing Image > Mode > Grayscale. Only 8-bit grayscale images can be
1
converted to duotones.
2 Choose Image > Mode > Duotone.
In the Duotone Options dialog box, select Preview to preview the image.
3
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