Difference key between two inputs: where A and B diverge past a threshold, output B and a mask; where they match, keep A.
Common Key compares inputs A and B per RGB channel. Pixels whose absolute difference meets or exceeds the threshold in any channel form a mask. Outside that mask the result keeps A; inside it takes B. The alpha channel is the difference mask.
Turn on alphaOnly to always pass B’s RGB while still writing the difference into alpha. Threshold controls how sensitive the compare is (small values catch subtle shifts).
Use it to isolate changes between two similar plates, build a holdout or garbage from a reference frame, or drive downstream keys and merges from a simple A/B delta without a full keyer stack.