Compression

Removing data a viewer will not miss, to make a file small enough to travel. Push it too far and the image begins to lie.

Compression is negotiated forgetting: the encoder discards what the eye statistically will not miss, gradients smooth, grain first against the wall, and buys travel weight with the losses. Done well it is invisible; done greedily the image starts inventing, banding skies and smearing shadows.

The image begins to lie is the operative warning for dark, atmospheric work like ours, where everything lives in the low tones compression attacks first. The working rules: compress from a clean master, never from a compression; keep texture as a surface layer rather than baked grain the encoder must fight; and judge results on the worst screen, not the edit suite's.