Duplex images are used to enlarge the tonal value range of a grayscale image in print. A black/white reproduction, for example, can contain up to 256 grayscales. The technical limitations of the print process mean that only around 50 levels, for example, can be depicted. To increase the number of grayscales, the entire brightness spectrum of duplex images is divided into two ranges which are represented by two different colors. In the simplest case, black ink is used for the dark hues, while gray is used for the brighter ones. However, a hue is often used for the bright areas. This gives the image a certain color toning which also enhances the level of contrast.
- Duplex Images