The Dodge tool and the Burn tool lighten or darken areas of the image. These tools are based on a traditional darkroom technique for regulating exposure on specific areas of a print. Photographers hold back light to lighten an area on the print (dodging) or increase the exposure to darken areas on a print (burning). The more you paint over an area with the Dodge or Burn tool, the lighter or darker it becomes.
Note:
Applying the Dodge tool or Burn tool to the background layer permanently alters the image information. To edit your images nondestructively, work on a duplicate layer. For information on duplicating layers, see Layer Basics.
or
the Burn tool 
.
to
use the brush as an airbrush. Alternatively, select the Airbrush
option in the Brush panel.
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