Photographic-Lighting Color Balance

Photographic-Lighting Color Balance

      This camera color-filtration technique provides the correct filtration, based on the color of the lighting, regardless of the color of the subject.  A subject can be photographed on green background, or red background, with the same correct color balance of the subject.  

      When driving at night after a rain, water reflects car headlights, tail lights, neon signs, street lights, the moonlight, etc.  Reflections off these puddles and many other materials (glass, plastic, paint,  grass, wood, floors, cars, pavement, etc.) are partially or even highly polarized and are easy to analyze.  

Example:

      To photograph this still-life scene the camera needs to ignore the subject colors and color balance for the illuminant only.  

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The color negative of the normal white-light photograph above contains the colors of the objects, and the reflections of the light sources.		The scene viewed through a rotating polarizing filter transmits the colors of the objects, and selectively transmits or blocks the polarized reflections of light sources.

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	When added together, the "difference image" eliminates the colors of the objects but leaves the reflections from various light sources that can be analyzed for color.

      This technique compares the direct view of the scene to another view through a polarizing filter.  The camera electronics creates a "difference" signal (basically subtracting one image from the other) which negates the colors of the objects, revealing only the colors of the reflections.  The subject colors are canceled, and only the reflected illumination, not blocked by the polarizing filter, remains.  The circuitry then adjusts the camera for the average color of scene illumination for the best overall color balance.