Range Mask
A refinement that limits a local adjustment to pixels within a specified colour, luminance or depth range.
In depth
Range masking solves the graduated filter's oldest problem: a gradient across a horizon can be told to affect only the tones that belong to the sky, leaving a protruding tree untouched. It converts a crude geometric selection into one that follows the actual content of the frame.
Examples in practice
A luminance range mask on a sky gradient keeps a silhouetted pylon from being darkened along with the clouds.