The Calculations effect combines channels of one layer with the channels of a second layer.
Input Channel: The channel to extract and use as input to the blending operation. RGBA displays all channels normally. Gray converts all color channel values for a pixel to the luminance value of the original pixel. Red, Green, or Blue converts all color channel values for a pixel to the value of the selected color channel for the original pixel. Alpha converts all channels to the value of the alpha channel for the original pixel.
Invert Input: Inverts the layer (subtracts each channel value from 1.0) before the effect extracts the specified channel information.
Second Layer: The control layer with which Calculations blends the original layer.
Second Layer Channel: The channel to be blended with the input channels.
Second Layer Opacity: The opacity of the second layer. Use a setting of 0% for the second layer to have no influence on the output.
Invert Second Layer: Inverts the second layer (subtracts each channel value from 1.0) before the effect extracts the specified channel information.
Stretch Second Layer To Fit: Stretches the second layer to the dimensions of the original layer before blending. Deselect to center the second layer on the original layer.
Preserve Transparency: Ensures that the alpha channel of the original layer isn’t modified.
Blending Mode: The method that is used to blend the two images together.