A Chroma-Key System Insensitive to Variations of the Background Illumination

Conventional chroma-key systems derive the chroma-key switching signal from chrominance-type signals. Because such signals are luminance-dependent, this method involves stringent requirements for stage build-up and background illumination. A novel chroma-key system is described, based on luminance-independent chromaticity criteria. With this system, requirements for scene build-up and background illumination are considerably alleviated, to the great benefit of the studio artist seeking to increase his design freedom. Topics discussed include: formation of the chroma-key switching signal, errors due to the employment of chrominance signals, improvement of chroma-keying by chromaticity-based switching, and prevention of false keying in dark parts of the scene. Data for plotting loci on the CIE x-y chromaticity diagram are derived.

Print ISSN

0036-1682

Published

1977-03

Content type

Original Research

DOI

10.5594/J13220