The Luma Key creates transparency for darker values in the image, leaving brighter colors opaque. Use the Luma Key to create a subtle superimposition or to key out dark areas.

Adjust the following settings as necessary:

Threshold

Specifies the range of darker values that are transparent. Higher values increase the range of transparency.

Cutoff

Sets the opacity of nontransparent areas specified by the Threshold slider. Higher values increase transparency.

You can also use the Luma Key to key out light areas by setting Threshold to a low value and Cutoff to a high value.