Adobe Photoshop CS4 - Manual (Page 502)

495 USING PHOTOSHOP CS4
Printing
Last updated 1/10/2010
Modify the duotone curve for a given ink
In a duotone image, each ink has a separate curve that specifies how the color is distributed across the shadows and
highlights. This curve maps each grayscale value in the original image to a specific ink percentage.
1 To preview any adjustments, select the Preview option in the Duotones Options dialog box.
2 Click the curve box next to the ink color box.
The default duotone curve, a straight diagonal line, indicates that the grayscale values in the original image map to an
equal percentage of ink. At this setting, a 50% midtone pixel is rendered with a 50% tint of the ink, a 100% shadow is
rendered in 100% color, and so on.
3 Adjust the duotone curve for each ink by dragging a point on the graph or by entering values for the different ink
percentages.
• In the curve graph, the horizontal axis moves from highlights (at the left) to shadows (at the right). Ink density
increases as you move up the vertical axis. You can specify up to 13 points on the curve. When you specify two
values along the curve, Photoshop calculates intermediate values. As you adjust the curve, values are automatically
entered in the percentage text boxes.
• The value you enter in the text box indicates the percentage of the ink color used to represent the grayscale value in
the original image. For example, if
you enter 70 in the 100% text box, a 70% tint of that ink color is used to print
the 100% shadows.
4 Click Save in the Duotone Curve dialog box to save curves created with this dialog box.
5 Click Load to load these curves or curves created in the Curves dialog box, including curves created using the
Arbitrary Map option.
You can use the Info panel to display ink percentages when you’re working with duotone images. Set the readout mode
to Actual Color to determine what ink percentages will be applied when the image is printed. These values reflect any
changes you’ve entered in the Duotone Curve dialog box.
More Help topics
“ Curves overview ” on page 168
Specifying overprint colors
Overprint colors are two unscreened inks printed on top of each other. For example, when you print a cyan ink over a
yellow ink, the resulting overprint color is green. The order in which inks are printed, as well as variations in the inks
and paper, can
significantly affect the final results.
To predict how colors will look when printed, use a printed sample of the overprinted inks and adjust your screen
display accordingly. Keep in mind that this adjustment affects only how the overprint colors appear on-screen, not
when printed. Before adjusting these colors, make sure to calibrate your monitor.
Adjust the display of overprint colors
1 Choose Image > Mode > Duotone.
2 Click Overprint Colors. The Overprint Colors dialog box shows how the combined inks will look when printed.
3 Click the color swatch of the ink combination that you want to adjust.
4 Select the desired color in the Color Picker, and click OK.
5 Repeat steps 3 and 4 until you are satisfied with the ink combination. Then click OK.