What is a Histogram in Photography?

The benefits of digital photography are numerous. One key component to digital photography is the ability to view the exposure of your photograph on a histogram. The graphical representation of the data collected by the digital sensor instantly lets the photographer know if their image is over, under or perfectly exposed. The histogram reveals instant information about the highlights, midtones and shadows of the image, right after taking the picture. If needed, the photographer may choose to reshoot the photo on the spot after making a few adjustments to the exposure. A quick look at the new histogram will let the photographer know how the exposure adjustments have effected the photograph.

Identification

A histogram in photography looks like a chart. A typical, well exposed photo, looks like a hill. The peak of the hill will be positioned in the center of the graph near the midtones. Data should reach to both ends of the graph, showing detail in the highlights and the shadows of the photo. The majority of the data shouldn't be skewed to the left or the right. Data skewed far to the right would indicate an over exposed, or very bright, photo. Data skewed to the left on the graph would indicate a very under exposed, or dark, photo.

Features

Three key components to a histogram in photography are the highlights, midtones and shadow information. The data represented on the left end of the histogram represents the shadows. The data collected in the center of the histogram represents the midtones of the photo. The data collected to the far right of the graph gives you information about the highlights in the photo. An even distribution of data on the histogram, with more data collected at the center, is preferred for most photos.

Types

Histograms regarding photography may be viewed in two places. When editing a photograph in photo editing software, you can view the image data as a chart, or histogram. In most photo editing software packages, you can then alter the digital image by adjusting the sliders under the histogram.
During the playback mode of a digital camera, especially DSLR cameras, you can view histograms to get a quick indication of you exposure. These are viewed on the LCD preview screen where you review your photos.
Histograms are able to represent digital images in several color modes, including RGB, CMYK, grayscale and lab color.

Function

Histograms relay data about the photo in a graphical way, so you can instantly tell if your exposure is what you want.

Benefits

Viewing a histogram on the back of your camera while taking pictures gives you vital data about the exposure of your photo instantly. This allows you to make exposure adjustments at the time of picture taking, so you can get a better picture.