How to Use Monotone, Duotone, Tritone, and Quadtone in Photoshop CS6
Adobe Photoshop Creative Suite 6 has the ability to help you create black and white images. However, there are multiple options for doing this that are not limited to Grayscale:
Uses: Because printing presses can print only about 50 gray levels per ink color, duotones and multitones — which use two to four inks — are used to increase the range of tones of grayscale images. Duotones and multitones are often created by using black and spot colors (premixed inks), although you can also use process colors.
File formats: The only file formats that can save duotones, tritones, and quadtones are native Photoshop, Photoshop 2.0, EPS, PDF, Large Document Format, or Photoshop Raw.
These modes create one-color, (monotone), two-color (duotone), three-color, and four-color (quadtone) images. Photoshop lumps all the various tone modes under duotone. You can find a pop-up menu in the Duotone options dialog box, from which you can select the various options.
Unlike RGB and CMYK images, in which the components of the image display with different colors, the monotones, duotones, tritones, and quadtones have the colors mixed throughout the image. The colored inks are often used to reproduce tinted grays, not the different colors you find in RGB and CMYK images.
To access the Duotone mode, you must first convert the color image to grayscale. Then, choose Image→Mode→Duotone. In the dialog box that appears, select Monotone, Duotone, Tritone, or Quadtone from the pop-up menu. Then, select ink colors — either spot or process — by clicking the appropriate swatches.
Finally, you can adjust the Curves settings by dragging the graph line. This tells Photoshop how to distribute the ink(s) among the various tones. You don't have access to the individual color channels in Duotone mode. The only manipulation you can do in that mode is to specify the Curves settings.
If you're new to these modes, you need to know that Photoshop offers numerous preset duotones, tritones, and quadtones. To access these presets, select one from the Preset pop-up menu. Sometimes, printing these types of images can be challenging, so starting with these presets is a good idea if you're inexperienced.