Adaptive: Adapts radius to image or selection content (using Histogram). If this option is checked, radius slider is not efficient. It renders a result smoother than with radius alone.

Recursive: Repeats filter action which gets stronger.

Radius: Sets size of action window from 1 (3x3 pixels) to 20 (41x41). This window moves over the image, and the color in it is smoothed, so imperfections are removed.

Black level: Removes pixels darker than set value (0-255).

White level: Removes pixels whiter than set value (0-255).