A pellicle is a very thin, semi-transparent film used in some one-shot colour cameras as a semi-reflecting surface. It allows light to pass through while simultaneously reflecting a portion onto a secondary sensor or film plane, enabling multiple exposures or simultaneous capture of different colour channels.
Pellicles were particularly useful in early colour photography and cinematography, where capturing separate colour components in a single shot was essential. Today, while largely replaced by modern digital sensors, pellicle technology remains an interesting part of photographic history and optical engineering.