Contrast: Amount of contrast

Hue/Saturation
Changes color range of (a part of) the color spectrum

Edit: Part of the color spectrum to edit
Hue: Shift on the color circle
Saturation: Shift from the center of the color circle
Lightness: Intensity of the colors

Invert
Inverts the selected layer

Exchange channels
Exchanges Red, Green and Blue channels

Red: Source of the new red channel
Green: Source of the new green channel
Blue: Source of the new blue channel

Cutoff channel
Cuts off maximum channel range

Apply to: Channel to cutoff
Cutoff: Maximum range of the selected channel

Range channel
Changes active range of a channel

Apply to: Channel to specify range
Low: Starting value of the range
High: Ending value of the range

Channel to RGB
Converts a channel to a RGB layer

Apply to: Channel to use as source
Red Start: Minimum red value
Red End: Maximum red value
Green Start: Minimum green value
Green End: Maximum green value
Blue Start: Minimum blue value
Blue End: Maximum blue value

Channel to phong
Converts a channel to a RGB layer using phong illumination

Apply to: Channel to use as source
Red: Amount of red
Green: Amount of green
Blue: Amount of blue
Light: Light applied to this layer
Reflection: Amount light reflected by this layer
Ambient: Ambient light