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How to Read an RGB Histogram

A histogram is a graphical representation of the exposure of a digital picture. Depending on the camera you are using, you may be able to view a standard histogram that will give you a reading on the overall exposure of the image. Or you may be able to view a RGB (Red, Green, Blue) histogram that will provide you with reading on the color saturation of your image. Understanding how to read RGB histograms will assist you in good color management.

Instructions

- 1
  Read the histogram from the left to the right and from the bottom to the top for each different color channel. If the histogram has more data to the left of center it is indicating the picture is dark. When the data is right of center it is indicating the picture is bright. This does not necessarily mean that the image is over- or underexposed. A properly exposed low key image will be weighted from the middle to the left. Look at each channel and see where the histogram is for that color. If you are shooting a sunset, the red channel will be weighted from the middle to the left.
- 2
  Review the information in the histogram and the actual image. If the image is of a sunset or dark evening sky, the data in the histogram will be to the left end of the graph, indicating the picture is correctly exposed. If the picture is of a bright day and the data in the histogram is to the left of center, the picture is potentially underexposed.
- 3
  Read from the bottom up on each channel. Staying with the sunset example, the read channel will not only be heavily weighted from the middle to the left, it will also occupy the most space in the histogram as sunsets tend to be warmer in color. In this example you would expect the green and blue channels to be thinner but also on the left side of the middle point of the histogram.

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