Orange Mask
The integral orange-coloured layer in colour negative film that corrects for imperfections in its dyes.
In depth
The cyan and magenta dyes formed during development absorb some light they should transmit, which would degrade colour reproduction. The mask compensates by adding a complementary correction across the whole frame. It is why negatives look orange, why they must be inverted with a film-specific profile, and why scanning them well is harder than scanning slides.
Examples in practice
Inverting a colour negative without accounting for the orange mask produces a strongly cyan-blue image.