What does a histogram show in photography?

• A. The tonal distribution from shadows to highlights across the image
• B. The frequency of autofocus performance
• C. The histogram shows exposure value histogram of the camera's file size
• D. The color histogram per channel

Answer: (B)

The main idea behind a histogram in photography is to show how brightness values are distributed across an image. The horizontal axis represents tonal range from shadows on the left to highlights on the right, with midtones in the middle. The height of the graph at each brightness level tells you how many pixels have that brightness. This helps you judge exposure and tonal balance at a glance—if most data pile up on the left, the image may be underexposed; if on the right, overexposed; a spread across the middle suggests a balanced exposure.

Note that you can also have color histograms that display the distribution for each color channel, but the standard histogram is about brightness. It isn’t a measure of autofocus performance or file size or an “exposure value histogram” related to size.