There are a range of adjustments which can be applied to your photo as a new layer for corrective or creative purposes.
Adjustments are applied to your image from the Adjustment panel and most include customizable settings alongside general adjustment options.
Adjustment layers only affect layers which are below them. Alternatively, you can make an adjustment a child of a layer (or layer group), thereby affecting that layer (or layer group) only.
Some adjustments (i.e., Curves, Levels, or Channel Mixer) can be made in any colour space independently of the document colour space.
The following general settings are available from all adjustment dialogs:
On the Adjustment panel, select an adjustment.
The adjustment is added directly above the selected layer or at the top of the stack if no layer was selected.
You can replace an applied adjustment of the same type by selecting a new preset or custom adjustment from the bottom of the Layers panel. This maintains the adjustment layer's position in the layer stack.
Click Adjustments and select an adjustment from the pop-up menu.
The adjustment is added directly above the selected layer.