Cross-processing
Deliberately developing film in chemistry intended for a different process, producing extreme colour and contrast shifts.
In depth
Running slide film through C-41 gives high contrast, blown highlights and strong colour casts that vary by emulsion; running negative film through E-6 gives flat, muted results with an orange overlay. The effects are unpredictable and unrepeatable across film stocks, which was much of the appeal in the 1990s fashion and music photography that popularised it.
Examples in practice
Slide film cross-processed in C-41 produces searing yellow-green highlights and cyan shadows.