This allows you to select an additional input layer or channel, that will be used to compute the lens blur. Clicking on the square picture allows you to select from a list of available layers and channels. The Aux will only be used if this setting is enabled.

The size of the blur radius.

Relative highlight strength.

Here you can set the minimum and maximum values for highlighting. It can be set either by dragging the black and white triangles, or inputting exact values into the number entry fields.

If enabled, this limits the output to the input extents.

If enabled, use linear mask values.