Title: Electronic composite photography with color control

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Abstract: Improved electronic compositing procedures and apparatus are described, ed typically on the blue screen process and suitable for processing motion pictures of professional quality and the like. The invention provides compensation for color impurity in the backing illumination over a continuous range of effective transparencies of the foreground scene. Applicant's previous method for limiting the blue video component for the foreground scene to permit reproduction of light blue foreground objects is improved by a dual limitation criterion which simultaneously suppresses blue flare light from the backing reflected by foreground objects of selected colors, typically including grey scale and flesh tones. The control signal for attenuating the background scene is developed as a difference function predominantly only at areas occupied by opaque or partially transparent foreground objects, and is developed predominantly as a ratio function at unobstructed backing areas, thereby compensating undesired variations in brightness of the backing illumination, while permitting desired shadows on the backing to be reproduced in the composite picture.


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