White Balance examples

[Mike McCarty]

The following is from the instructions which came with my gray card:

"Light meters and camera meters are calibrated to average the light reflected off a scene so that the <film> will record the scene as average. The average scene will reflect approximately the same as a gray card or 18%. However, if the scene is not average, it is necessary to make an adjustment to the setting of your meter. This is the time to use your gray card. It will help you determine the proper exposure adjustments."

The following is from my D70 instruction book regarding white balance. Procedures will vary from camera to camera:

The color of the light reflected from an object varies with the color of the light source. The human brain is able to adapt to changes in the color of the light source, with the result that white objects appear white whether seen in the shade, direct sunlight, or under incandescent lighting. Unlike the film used in film cameras, digital cameras can mimic this adjustment by processing images according to the color of the light source. This is known as "white balance."

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Preset white balance is used to compensate for light sources with strong color contrast. A neutral gray [gray card] or white object is placed under lighting that will be used in the final photograph and the white balance is measured by the camera. [my camera will also allow you to use the color balance from an existing stored photo]

I take this to mean that white balance is an extension of exposure. A "next step" that film could not achieve. Where exposure deals with the amount of light, white balance deals with the color, or temperature, of that light.

Some films were better adapted to certain types and temperatures of light than others, and if you didn't do your homework to match your roll of film to the task at hand it just came out wrong. The same could be said for digital except that we can make our adjustments (much more precise adjustments than the range of film choices would offer) per image, not just per roll of film. Not unlike film speed, or ISO.