The Convert to Grayscale node converts color  to the gamma.


Convert to Grayscale

Figure 1: Apply gamma curve Node


Convert to Grayscale Parameters

Enabled - Whether this layer is applied or skipped.

Attach to layer - When selected, this layer modifies the input of the next lower layer that is not itself attached to a layer. Otherwise, it applies to the output of the next lower layer.

Gamma - The gamma value used. The equation applied is: output = pow(input, 1/gamma).

Opacity - The opacity channel used to control the transparency of this layer.

Blend mode - The blend mode used to mix the RGB values of this layer with those of the background.