Histograms are a graphic representation of the levels of light in your photo. They’re a great tool for understanding just how the light in your photo is balanced and can help you to create the perfectly exposed and balanced photograph.
To see just how histograms display color and light information we will dissect the histogram below which represents the light tones of the image above.
The most common type of histogram illustrates black and white tones, but it is not uncommon to see a histogram that separates an image into it’s core colours as well. To understand the black and white histogram above we must first imagine that the image at the top is desaturated and presented in black and white.
The horizontal axis represents the dark and light tones and the vertical axes shows what portion of the image holds that particular tone. The photograph above is evidently dark and the top and bottom of the image hold a lot of black shadows.
On the histogram we can see that there is a peak on the far left which indicates that those dark shadows are the most prominent tones in the image.
On the far right of the histogram we can see that there are minimal highlights. This again can be seen in the photograph as there are no significant white points.
Due to it’s significant shadows this photograph would be regarded as underexposed. A correctly exposed photo will have the majority of the histogram in the ‘Midtones’ section and be evenly spread throughout the graph.
Histograms can be a very handy tool when you’re trying to balance the exposure of your photo. Just remember that it should only be used as a guide and sometimes the eye serves as a better judge.