Photographic Color Balance

 

Photographic Color Balance

 

      This is a photo technique to provides the correct color balance, based on the color of the lighting, regardless of the color of the subject.  

     The trick is to subtract a polarized view of the scene, from an unpolarized version of the same scene.  The “difference image” is that of the lighting.  The color of the subject is the same in both images and therefore cancel each other out.  The camera then sets the color balance for just the lighting.

 

      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,pp cars, wet pavement, etc.) are partially or even highly polarized and are easy to analyze.  

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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 of 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 are analyzed for color.