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Understanding Printing Terminology” section, so here’s a quick recap: A duotone is a grayscale image printed with two inks. This technique expands the depth of the image by allowing additional shades for highlights, shadows, and midtones. If you’ve seen a glossy magazine ad for perfume, designer clothing, a car, or just about any other overpriced commodity, you’ve seen a duotone. Words like rich, luxurious, and palpable come to mind.Photoshop also enables you to add a third ink to create a tritone and a fourth ink to create a quadtone. Color Plate 18-1 shows an example of each of these. Figure 18-12 shows a detail from the image printed in its original grayscale form. See the difference?
Figure 18-12: A sheet of imperforate souvenir stamps from 1936, scanned in grayscale on a Umax PowerLook 3000 desktop scanner.
Creating a duotone
To convert a grayscale image to a duotone, tritone, or quadtone, choose ImageMode Duotone. Photoshop displays the Duotone Options dialog box shown in Figure 18-13. By default, Monotone is the active Type option, and the Ink 2, Ink 3, and Ink 4 options are dimmed. To access the Ink 2, 3, or 4 options, select Duotone, Tritone, or Quadtone, respectively, from the Type pop-up menu.
Figure 18-13: The Duotone Options dialog box enables you to apply multiple inks to a grayscale image.
Specify the color of each ink you want to use by clicking the color swatch associated with the desired ink option. You can define colors with the Color Picker or with the Custom Colors dialog box. It’s easy to switch back and forth between the two by clicking the Custom or the Picker button, depending on which dialog box you currently are using.Photoshop takes the guesswork out of creating a duotone by previewing your settings in the image window when the Preview check box is turned on. Keep in mind that the preview may not exactly match your output when using certain Pantone inks. (This is a common problem when previewing Pantone inks in any program, but it’s always a good idea to keep in mind, particularly because Photoshop mixes inks to create its duotone effects.) The next time you create a duotone, Photoshop displays the same colors you defined in your last visit to the Duotone Options dialog box.When creating duotones, tritones, and quadtones, prioritize your inks in order — from darkest at the top to lightest at the bottom — when you specify them in the Duotone Options dialog box. Because Photoshop prints inks in the order in which they appear in the dialog box, the inks will print from darkest to lightest. This ensures rich highlights and shadows and a uniform color range.
After selecting a color, you can use either of two methods to specify how the differently colored inks blend. The first and more dependable way is to click the curve box associated with the desired ink option. Photoshop then displays the Duotone Curve dialog box, which works just like the Transfer Functions dialog box described back in the “Specifying a transfer function” section of this chapter. This method permits you to emphasize specific inks in different portions of the image according to brightness values.For example, Color Plate 18-1. The Navy Blue color is associated with only the darkest brightness values in the image; Deep Red peaks at about 80-percent gray and then descends; Teal covers the midtones in the image; Orange is strongest in the light values. The four colors mix to form an image whose brightness values progress from light orange to olive green to brick red to black.The second method for controlling the blending of colors is to click the Overprint Colors button. An Overprint Colors dialog box appears, showing how each pair of colors will mix when printed. Other color swatches show how three and four colors mix, if applicable. To change the color swatch, click it to display the Color Picker dialog box.
The problem with this second method is that it complicates the editing process. Photoshop doesn’t actually change the ink colors or curve settings in keeping with your new specifications; it just applies the new overprint colors without any logical basis. And you lose all changes made with the Overprint Colors dialog box when you adjust any of the ink colors or any of the curves.To return and change the colors or curves, choose Image Mode Duotone again. Instead of reconverting the image, the command now lets you edit the existing duo- tone, tritone, or quadtone.
Reproducing a duotone
If you want a commercial printer to reproduce a duotone, tritone, or quadtone, you must print the image to color separations, just like a CMYK image. Because you already specified which inks to use and how much of each ink to apply, however, you needn’t mess around with all those commands in the Color Settings dialog box. Just take the following familiar steps.
STEPS: Printing a Duotone, Tritone, or Quadtone
Choose the printer you want to use. Select a printer as described previously in this chapter.
Set the page size, orientation, and printer marks options. In the Page Setup dialog box (Ctrl+Shift+P or z -Shift-P), specify the size of the pages and the size and orientation of the image on the pages, as described in “The Page Setup dialog box” section, earlier in this chapter. Then select the Registration Marks option in the Print with Preview dialog box (Ctrl+Alt+P or z -Option-P).
Adjust the halftone screens, if desired. If you’re feeling inventive, click the Screen button to change the size, angle, and shape of the halftone screen dots for the individual color plates, as described previously in the “Changing the halftone screen” section.
Specify output to color separations. Still in the Print with Preview dialog box, choose Color Management from the pop-up menu. Then choose the Separations option from the Profile pop-up menu in the Print Space section of the dialog box to print each ink to a separate sheet of paper or film.
To prepare a duotone to be imported to QuarkXPress, Illustrator, or some other application, save the image in the EPS format, as described in the “Saving an EPS image” section of Chapter 3. As listed back in Table 4-1 of Chapter 4, EPS is the only file format other than the native Photoshop format that supports duotones, tri- tones, and quadtones.
Editing individual duotone plates
If you’ll be printing your duotone using CMYK colors and you can’t quite get the effect you want in the Duotone Options dialog box, you can convert the duotone to the CMYK mode by choosing Image Mode CMYK Color. Not only will all the duo- tone shades remain intact, but you’ll also have the added advantage of being able to tweak and add colors using Photoshop’s standard color correction commands and editing tools. You can even edit individual color channels, as described in Chapter 4.If your duotone includes Pantone or other spot colors, converting to CMYK is not an option. But you can still access and edit the individual color channels. To separate the duotone inks into channels, choose Image Mode Multichannel. Each ink appears as a separate spot color in the Channels palette, as shown in Figure 18-14. You can experiment with different color combinations by turning eyeball icons on and off. You can even switch out one spot color for another by double-clicking the channel name and then clicking the color swatch.
Figure 18-14: Here I chose Image Mode Multichannel to separate my quadtone into four independent spot-color channels, and then double-clicked the Deep Red channel to access the Spot Channel Options dialog box.
To save a duotone converted to the multichannel mode, you have just two options: native Photoshop (as always) and DCS 2.0. For complete information on the latter, read the “QuarkXPress DCS” section in Chapter 3.
