You can use the Posterize effect to reduce the number of brightness levels in your image. You can select or change the Posterize options to apply this effect to your image, and save your options as a preset for use at another time.
To apply a Posterize effect:
- In Edit mode, in the Add group, click Special Effect.
- Click Posterize.
- On the Posterize tab, drag the Brightness levels slider to adjust the variance of colors in the image. The lower the value, the fewer colors used in the image.
- Do one of the following:
- Click Done to accept your changes and close the pane.
- Click Cancel to discard your changes and close the pane.