Healthy Histogram Appetizer
A histogram is a graph that represents the distribution of the brightness information in a photo. The left side represents shadows. The right side represents highlights. If either side has spikes that means clipping has occurred. Clipping means loss of detail. Clipping of the shadows means 100% black, and clipping of the highlights means 100% white.
Generally, a well exposed image has a solid black hump that spreads from one side to the other, and peaks toward the right. Many exceptions to this. Some clipping is acceptable, such as specular highlights (reflections on a glass, etc.). Clipping is also acceptable when using artistic license to achieve a special effect.
One example of what has come to be acceptable clipping is a portrait of a colorfully dressed child outdoors with a blown out white sky. The main subject matter is the child. Often an artist wants a child to have clean bright skin tones. When using natural lighting you often have to choose between exposing for the sky, or exposing for the child. If you expose for a bright sky, the child might be dark. If you expose for the child, the sky might blow out. You could combine two exposures and get the best of both worlds, or you may prefer pushing a child portrait of this nature to more of a high key image that shows histogram information humping toward the right.
Written for the April 2008 PPGPB Newsletter ©2008 Linda King
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