Curves adjustment

Apply this adjustment via the Adjustment button on the Layers panel or via Layer > New Adjustment.

You can use the Curves adjustment to manipulate individual color channels. The adjustment can be used on placed images as well.

The following settings can be adjusted in the dialog:

Select a color mode (GREY/RGB/CMYK/LAB) from the first pop-up menu.
Specify a single color channel to apply the adjustment to, including the layer's alpha channel. Master (the default choice) applies the adjustment to all color channels, excluding the alpha channel.
Picker—click to activate the picker which allows you to drag on the image to modify the adjustment. Regardless of the color model set, a click-drag places a node on the curve in relation to the selected pixel intensity; a 1x1 pixel area is considered. Secondly, dragging up (to lighten the image) or dragging down (to darken it) modifies the adjustment. The curve graph will update accordingly.
X—accurately positions any added and currently selected node on the X-axis of the graph.
Y—accurately positions any added and currently selected node on the Y-axis of the graph.
Min and Max are the input minimums and input maximums and let you determine the range/threshold of values that are affected by the adjustment. It uses a normalized 0-1 range (regardless of bit depth) but setting Max to >1 allows the adjustment to manipulate HDR values as well. They can be also be used to fine-tune the manipulated tonal range in 8-bit and 16-bit documents.

To adjust a curves graph:

On the curves graph, do any of the following: