Photoshop Wiki

Adjustments are widespread changes to an image or layer. Many adjustments alter contrast, tone, or color balance. If a selection is active, the adjustment is limited accordingly.

Adjustments differ from filters in that each pixel is analyzed individually (relative to the color mode or space), rather than in comparison to others.


Adjustments have been present in every version of Photoshop, increasing in number with each subsequent release:

Adjustment Version
Levels 0.63
Color Balance 0.63
Hue/Saturation 0.63
Brightness/Contrast 1.0
Curves 1.0
Replace Color 3.0 or earlier
Selective Color 3.0 or earlier
Auto Levels 3.0 or earlier
Desaturate 3.0 or earlier
Variations 3.0 or earlier
Invert 4.0
Equalize 4.0
Threshold 4.0
Posterize 4.0
Channel Mixer 5.0
Shadow/Highlight CS

Starting with Photoshop 4.0, Adjustment Layers became available, allowing adjustments to be non-destructive.

In Photoshop CS4, adjustments were finally given their own workspace panel.