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Duotones
About duotones
Convert an image to duotone
Modify the duotone curve for a given ink
Specifying overprint colors
Adjust the display of overprint colors
Saving and loading duotone settings
View the individual colors of a duotone image
Printing duotones
Exporting duotone images to other applications
About duotones
In Photoshop, duotone refers to monotones, tritones, and quadtones as well as duotones. Monotones are grayscale images printed with a single,
non-black 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.
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.
Convert an image to duotone
1. Convert the image to grayscale by choosing Image > Mode > Grayscale. Only 8-bit grayscale images can be converted to duotones.
2. Choose Image > Mode > Duotone.
3. In the Duotone Options dialog box, select Preview to preview the image.
4. For the Type option, select Monotone, Duotone, Tritone, or Quadtone.
5. Click the color box (the solid square) to open the color picker, then click the Color Libraries button and select an ink book and color from the
dialog box.
Note: To produce fully saturated colors, specify inks in descending order—darkest at the top, lightest at the bottom.
6. Click the curve box next to the color ink box and adjust the duotone curve for each ink color.
7. Set overprint colors, if necessary.
8. Click OK.
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.
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
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