Adobe Photoshop CC 2014 v.14.xx - Manual (Page 437)

Note:
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Note:
1. Do one of the following:
Click the Threshold icon in the Adjustments panel.
Choose Layer > New Adjustment Layer > Threshold. Click OK in the New Layer dialog box.
The Properties panel (CC, CS6) or Adjustments panel (CS5) displays a histogram of the luminance levels of the pixels in the current
selection.
You can also choose Image > Adjustments > Threshold. But keep in mind that this method makes direct adjustments to the image
layer and discards image information.
2. In the Properties panel (CC, CS6) or Adjustments panel (CS5), drag the slider below the histogram until the threshold level you want
appears. As you drag, the image changes to reflect the new threshold setting.
Posterize an image
The Posterize adjustment lets you specify the number of tonal levels (or brightness values) for each channel in an image and then maps pixels to
the closest matching level. For example, choosing two tonal levels in an RGB image gives six colors: two for red, two for green, and two for blue.
This adjustment is useful for creating special effects, such as large, flat areas in a photograph. Its effects are most evident when you reduce the
number of gray levels in a grayscale image, but it also produces interesting effects in color images.
If you want a specific number of colors in your image, convert the image to grayscale and specify the number of levels you want. Then convert
the image back to the previous color mode, and replace the various gray tones with the colors you want.
1. Do one of the following:
Click the Posterize icon in the Adjustments panel.
Choose Layer > New Adjustment Layer > Posterize.
You can also choose Image > Adjustments > Posterize. But keep in mind that this method makes direct adjustments to the image
layer and discards image information.
2. In the Properties panel (CC, CS6) or Adjustments panel (CS5), move the Levels slider or enter the number of tonal levels you want.
Apply a gradient map to an image
The Gradient Map adjustment maps the equivalent grayscale range of an image to the colors of a specified gradient fill. If you specify a two-color
gradient fill, for example, shadows in the image are mapped to one of the endpoint colors of the gradient fill, highlights are mapped to the other
endpoint color, and midtones are mapped to the gradations in between.
1. Do one of the following:
Click the Gradient Map icon in the Adjustments panel.
Choose Layer > New Adjustment Layer > Gradient Map. Click OK in the New Layer dialog box.
You can also choose Image > Adjustments > Gradient Map. But keep in mind that this method applies the adjustment directly to the
image layer and discards image information.
2. In the Properties panel (CC, CS6) or Adjustments panel (CS5), specify the gradient fill you want to use:
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