What's Covered
Creating Spot Colors Using Third Party Plug-ins
Creating Spot Colors in Photoshop's Duotone Mode
Simulating Spot Colors in Photoshop's CMYK Mode

Spot colors, or "custom colors," are printed using pre-mixed inks, rather than reproduced by mixing cyan, magenta, yellow, and black (CMYK) inks. Each spot color requires its own film separation and press plate, which is coated with the pre-mixed ink.

Because Photoshop is a process-color (CMYK) application, you cannot assign spot colors to an image in Photoshop. However, you can prepare a Photoshop document to be separated on spot plates using a third-party plug-in, using Photoshop's Duotone mode, or by assigning spot colors to process channels in Photoshop's CMYK mode. This document describes each of these techniques.

Creating Spot Colors Using Third Party Plug-ins
The following third-party plug-ins for Photoshop enable you to prepare a Photoshop document for spot color printing.

- PhotoSpot by Second Glance
PhotoSpot is a set of plug-ins that can reduce the number of colors in an RGB or CMYK image, or produce eight color variations of stochastic separations. You can use PhotoSpot's Export command to create separations for individual colors, which you can print from Photoshop or import into another application (e.g., Adobe PageMaker, QuarkXPress) for printing.

- PlateMaker by A Lowly Apprentice
PlateMaker enables you to isolate custom colors into separate channels in CMYK, Indexed Color, or Multichannel modes, and then save the custom colors with your image in DCS 2.0 format. You can then separate the DCS image from a page layout application that supports DCS 2.0 (e.g., Adobe PageMaker 6.x, QuarkXPress 3.x).

Creating Spot Colors in Photoshop's Duotone Mode
If you want to apply spot colors to an entire image, rather than to specific area of the image, you can do so using Photoshop's Duotone mode, which is the only Photoshop mode that supports true spot color. In Duotone mode you can create monotones, duotones, tritones and quadtones, enabling you to use up to four spot colors. Monotones are grayscale images printed with a single, nonblack ink. Duotones, tritones, and quadtones are grayscale images printed with two, three, and four inks, respectively. In these types of images, custom inks are used to reproduce tinted grays rather than to reproduce discrete spot colors. You can choose from several libraries of custom spot color inks (e.g., Pantone Coated, Focoltone, Trumatch). For more information on Duotone mode, see the Adobe Photoshop User Guide.

Simulating Spot Colors in Photoshop's CMYK Mode
If you want to apply a spot color to a specific area of an image, rather than to the entire image, you can simulate up to four spot colors using the C, M, Y, and K channels in Photoshop's CMYK mode. You begin by converting an image to Grayscale mode and then CMYK mode, keeping all of the pixel information in the Black channel. Then, using Photoshop's selection tools, you isolate specific areas of the image to the C, M, or Y channels, which act as substitutes for spot color separations. You can then print the appropriate process separations from Photoshop or a page layout application, indicating to your commercial printer which spot color ink to use for each process separation.

Isolating Image Areas to CMYK Channels
To convert an image to CMYK mode and isolate areas to individual channels:
1. Open the image you want to prepare for spot color printing.
2. Choose Image > Mode > Grayscale (Photoshop 4.0) or Mode > Grayscale (Photoshop 3.0.x and earlier).
3. Choose File > Color Settings > Separation Setup (Photoshop 4.0) or File > Preferences > Separation Setup (Photoshop 3.0.x and earlier).
4. Note the Black Generation setting, then select Maximum from the Black Generation pop-up menu. (The Maximum setting ensures that all the pixel information will be on the Black channel when you convert the image to CMYK mode.)
5. Click OK.
6. Choose Image > Mode > CMYK Color (Photoshop 4.0) or Mode > CMYK Color (Photoshop 3.0.x and earlier).
7. Repeat step 3, then change the Black Generation option to the setting you noted in step 4.
8. Select an area of the image to which you want to apply a spot color. Make sure anti-aliasing is deselected in the options palette for the selection tool that you use.
9. Assign the selection to the C, M, or Y channel:
If your selection is black-and-white line art or a continuous-tone area (e.g., a photograph) that you want to fill with a solid color, do the following:
a. Click on one of the blank channels. You can select any empty channel, but it is a good idea to select the one whose color is closest to the spot color you'll use.
b. Choose Edit > Fill and fill the selection with 100% black, a percentage of black, or with a black-to-white gradient. (In a Photoshop color channel, 100% black represents 100% of the channel color, and 100% white represents 0% of the channel color.)

If your selection is a continuous-tone area (e.g., a photograph) and you want to retain its highlights and shadows (i.e., gray values), do the following:
a. Choose Edit > Copy to copy the selected area to the clipboard.
b. Click on one of the blank channels. You can select any empty channel, but it's a good idea to select the one whose color is closest to the spot color you'll use.
c. Choose Edit > Paste.

10. With the selection still active, click on the Black channel in the Channels palette, then press the Delete key to delete the selected area from the Black channel.
11. Repeat steps 8 to 10 for up to two additional spot colors.
12. Save the file as an EPS or TIFF graphic.

Displaying Spot Colors in CMYK Channels
You can change the display color of the C, M, Y, or K channels to match the spot color they represent, enabling you to preview the spot colors on screen. You use the Custom Colors and Printing Inks Setup dialog boxes to change the color values for the channels.

To change the display color of a channel:
1. Click the foreground color selection box in the toolbox to display the Color Picker dialog box.
2. Click Custom.
3. Select the desired spot color and click OK.
4. Choose File > Color Settings > Printing Inks Setup (Photoshop 4.0) or File > Preferences > Printing Inks Setup (Photoshop 3.0.x and earlier).
5. Select Custom from the Ink Colors pop-up menu.
6. Click the swatch next to the channel whose color you want to change. The Color Picker appears.
7. With the Color Picker dialog box still displayed, move the cursor over the foreground color selection box in the toolbox. The cursor changes to an eyedropper.
8. Click the foreground color selection box to sample the spot color. The channel color changes from its default color to the spot color. Click OK three times to exit the Printing Inks dialog box.
9. Repeat steps 1 to 8 to change the color value for other channels.
10. Before exiting the Printing Inks Setup dialog box for the last time, click Save, name the file, then click Save to save this printing inks setup.

NOTE: To return the printing inks to their default values, choose SWOP Coated from the Ink Colors pop-up menu in the Printing Inks Setup dialog box.

Printing the Image from Photoshop or a Page Layout Application
Once you've assigned specific areas of your image to the C, M, Y, and K channels, you can print process separations of the image from Photoshop, and then indicate to your commercial printer which spot color you want for each plate. You can also separate the image from a page layout application using the steps below.

NOTE: Because you will use the process separation plates to print spot colors, do not import the Photoshop image into a page layout document that contains process color elements.

To separate the image from another application:
1. In Photoshop, choose File > Preferences > General, select Short Pantone Names, then click OK.
2. Save the image as a TIFF or EPS graphic. If you save in EPS format, deselect Include Halftone Screen and Include Transfer Function in the EPS Format dialog box.
3. Import the image into the page layout application.
4. Set the screen angles recommended by your service provider or the manufacturer of your imagesetter or final output device.
5. Assign the appropriate spot color to the cyan, magenta, and yellow plates, according to the documentation provided with the application, or tell your commercial printer which spot color you want for each of the color plates.

To separate the image from Adobe PageMaker:
1. In Photoshop, choose File > Preferences > General, select Short Pantone Names, then click OK.
2. Save the image as a TIFF or EPS graphic. If you save in EPS format, deselect Include Halftone Screen and Include Transfer Function in the EPS Format dialog box.
3. Place the image into a new or existing PageMaker publication.
4. If the publication already contains one or more of the spot colors you'll use for the Photoshop image, redefine the spot colors in PageMaker so they print on the appropriate cyan, magenta, yellow, or black plate:
a. Choose Element > Define Colors (PageMaker 6.0x and earlier) or Utilities > Define Colors (PageMaker 6.5x).
b. Select a spot color used in the Photoshop image, then click Edit.
c. Select Process from the Type pop-up menu in the Edit Color dialog box.
d. Select CMYK from the Model pop-up menu.
e. Increase the percentage value for the process plate on which you want the spot color to print to 100, then change the other process color percentages to zero. For example, if you want the spot color to print on the cyan plate (i.e., you isolated the Photoshop elements to the C channel), then redefine the spot color as 100% cyan, 0% magenta, 0% yellow, and 0% black.
f. Click OK.
g. Repeat for any other spot colors defined in PageMaker that are used in the Photoshop image.

5. Choose File > Print, then click Color.
6. Select the Separations option. The Cyan, Magenta, Yellow, and Black inks are automatically selected in the Print Ink scroll box. If you want to print any spot colors on additional plates, make sure that they are also selected.
7. Make other print settings as desired, then click Print.
8. Indicate to your commercial printer which spot color you want to use for each process color plate.