Duotone

Duotone is a halftone reproduction of an image using the superimposition of one contrasting colour halftone (traditionally black) over another color halftone. This is most often used to bring out middle tones and highlights of an image. The most commonly implemented colours are blue, yellow, brown, and red.

Due to recent advances in technology, duotones, tritones, and quadtones can be easily created using image manipulation programs.

Duotone color mode in Adobe's Photoshop computes the highlights and middle tones of a monochrome (grayscale or black-and-white) image in one color, and allows the user to choose any color ink as the second color.

A fake duotone, or duograph, is done by printing a single color with a one-color halftone over it. This process is generally not preferred over a regular duotone, as it loses much of the contrast of the image.

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