Photographic Color Balance

 

Photographic Color Balance

 

      This is a photo technique provides the correct color balance, based on the color of the lighting, regardless of the color of the subject.  Ref: Notebook p115.

     The trick is to subtract a polarized version of the scene, from an unpolarized version of the 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.  

 

      Examples of what may seem to be hard to color balance scenes: wet streets, reflected car lights and neon signs, street lights, the moonlight, etc.  Reflections of puddles and many other materials (glass, plastic, paint, cars, wet pavement, etc.) are partially polarized and are easy to analyze.  

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Example:

        To photograph this 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 that 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.