You can use the Posterize effect to reduce the number of brightness levels in your image. Select or change the Posterize options to apply this effect to your image.
You can save your settings as a preset for future use.
To Apply a Posterize Effect:
You can right-click a slider to reset to the default value.
You can use the Edit Brush
to paint this effect onto specific areas of your image.
You can use the Gradient tool
to transition this effect across specific areas of your image.
You can use the Radial Gradient tool
to apply effects around, or directly to, a center point.