What Are Duotones?

When a grayscale digital image is converted to a halftone and printed with black ink on paper, the shades of gray that you created on your computer are represented by the size and concentration of dots. The black ink is still black, no matter what size you make the dot. It can t, however, represent all 256 levels of gray found in the grayscale image.

Duotones can help you achieve a wider tonal range in a grayscale image by using more than one shade of ink to fill in the gaps. You can enhance the detail and texture in an image. If you re printing a two-color book with halftones, adding the second color to the halftones can add an elegant touch. Duotones using a dark and a metallic ink can impart an opaque , antique quality, whereas lighter pastel shades might approximate a hand- tinted look or other variations, as you can see in Figure C28 in the color section.

Duotones do present one potential problem. Because two (or more) inks are being superimposed on one another, it is possible to generate too much ink. If the distribution of ink is not dealt with properly, it could saturate the paper and fill in the spaces between the fine halftone dots. That s why Photoshop s Duotone mode features a Curves palette in its dialog box, so that you can adjust each ink level individually ”but I ll get to that in a minute.