The Curves tool is used to adjust the relative values of pixels in the active selection or the active layer. The tool has various options available to help refine these changes.
Curves Tool Settings
There are four options here.
Value: Sets the changes to affect all pixel values.
Red: This setting makes changes to the Red channel only.
Green: This setting makes changes to the Green channel only.
Blue: This setting makes changes to the Blue channel only.
These buttons allow you to save Curves that you have created. They can be saved anywhere or with any filename and extension.
Curve type allows you to choose between Smooth or Free.
Smooth: This mode constrains the curve type to a smooth line with tension. This mode provides a more realistic render than Free mode.
Free: This mode allows free-hand drawing of the curve using your mouse. This mode provides more control than the Smooth mode.
The main editing area of the curves window provides the actual modification area of the tool. The curve can be changed using the mouse.
In Smooth mode, each click adds a node to the curve that can be moved by clicking and dragging.
In Free mode, the curve must be drawn by hand.