How to Read a Histogram

Your Histogram

No discussion of light in digital photography is complete without emphasizing one of the most wonderful features of digital photography that everyone is afraid of: the histogram. Don’t be afraid to use it, it is not that hard to understand and it will make a huge difference to the quality of your images since it provides you with information about flaws at a glance if you know how to read it.

After you make an image, you can review your shot in your LCD display to make sure you got what you wanted. This is a great tool for checking composition and focus. But not for exposure. The LCD just doesn’t give you an accurate impression of exposure and you might be disappointed when you see the image on your computer monitor later. Use the histogram!

It’s easy: the blacks are on the left, the whites are on the right, all the mid-tones are in between. All you really need to know is that a spike on either edge of the graph is bad.

If there is a spike on the left edge, as in the image above, it means part of your image is completely black. You may want to use your exposure compensation to adjust the exposure to the right to make it brighter (or you can change shutter speed or aperture if you are used to shooting in manual mode, but using exposure compensation does the same thing and it’s really easy to use). But remember that having part of your image completely black, especially for a night shot, is ok.

If there is a spike on the right edge, like in the image above, it means part of your image is completely white and contains no data. Never never never let any substantial part of your image go completely white. Because it contains no data at all, it will always remain a white spot no matter what you try to do in post-processing. It’s better to keep that graph off the right edge. Use your exposure compensation and move the slider to the left to darken the image. You only need to worry about this if the spike is right on the very edge of the histogram - if it spikes before the edge it is not a problem.