Expands deep samples along Z by pulling deep.front forward and pushing deep.back back by a single expand amount.
Deep Expander thickens deep data by adjusting sample bounds on the deep channel. It subtracts the expand value from deep.front and adds the same value to deep.back, so each sample spans a wider depth range.
Use it when deep holdouts or deep merges leave thin coverage, gaps, or fragile edges and you need more depth extent without rebuilding the deep pass. A single expand control drives both sides of the sample.
Drop it on a deep stream in the comp; front moves closer to camera and back moves farther by the same amount, leaving color and other deep channels unchanged.