Many digital cameras possess a histogram function that is unfamiliar in analogue photography. Careful quality control has been made possible through the histogram. Graphically it portrays a quick overview of a picture’s brightness values, in order to optimally judge the lighting.

If bright sunlight is glaring across the LCD monitor, then directly supervising the picture is difficult. Using the histogram, the picture quality can be judged from its tonal values. A histogram shows the picture’s brightness distribution in the form of a bar graph. The x-axis shows the light, mid-ranges, and shadow, while the y-axis shows how often each brightness value is identified.

The more often a certain brightness value appears, the higher the corresponding bar in the diagram. On the left of the x-axis are the values for the darker tones, while the values on the right represent the distribution of bright values. High bars on the left side of the diagram indicate an under-lit shot. While over-lit shots display high bars on the right side.

A picture that is too dark can be corrected with help of the exposure corrector by a positive value, for example +1. While the exposure corrector can be adjusted by a negative value if the picture is too bright. Moreover, using the x-axis one can also tell if the tonal value selection is being fully used. If certain bars are missing along the edges, then this can be due to a lowered range.

Of course the histogram can also consciously be used in order to take so-called high or low-key shots. These are shots that use over- or under-illumination as a speciall effects for their shot.

Some high-grade camera models (such as the new Lumix cameras from Panasonic) even allow for the use of histogram function before the shot. That way the photographer can already undertake the necessary exposure correction before pressing the photo release, and the picture is optimised from the first shot. This is especially helpful when only presented with one chance to get the shot.