Sign & Digital Graphics

January '17

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40 • January 2017 • S I G N & D I G I T A L G R A P H I C S DIGITAL PRINTING AND FINISHING DIGITAL GRAPHICS ors and excludes other colors from the alteration. The colors are divided into ranges of 90 degrees each, including the overlap—the amount that the colors adjacent to the target color on the color wheel are affected. The list contains col- ors by name: Master, Reds, Yellows, Greens, Cyans, Blues, and Magentas. When a specific color is selected from the list, the alteration is limited to col- ors within that range as in Figure 4. An adjustment slider appears between the two color bars, telling you which col- ors are being affected and letting you increase or decrease the range of hues affected by dragging the ramps to the left or right. The dark gray ramp encom- passes the colors that are most affected. The light gray ramp indicates the overlap of adjacent colors that are less affected. The ramps can be dragged to the left or right to expand or decrease the range. Limiting Colors The overall number of colors in an image can be limited to produce gor- geous posterized effects. The Posterize command can be applied directly to an image with the Image > Adjustments > Posterize command, or with a Poster- ize adjustment layer. If the posteriza- tion is applied to an RGB image there is no direct way of controlling how the colors are mapped because the Posterize function applies the chosen quantity of colors to each channel of the image. For example, if you enter 2 while working in an RGB image, six colors are produced (two per channel) as in Figure 5. These effects can be interesting but with no way to control the color that is produced they can be unpredictable. Figure 4: When a specific color is selected from the list, the alteration is limited to colors within that range. Figure 5: Posterize applies the specified quantity of colors to each of the three channels, usually producing unpredictable results.

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