Histograms not only appear in photography but are also found in statistics, physics, and others. Usually used to display the position of values/numbers in calculations, which in photography is light calculations. So the histogram will describe the light intensity in our photos.
You can use the histogram to help determine exposure when shooting. The graphic display is usually from left to right, and if it peaks on the left, it means your photo is under exposed or dark, but if it peaks on the right, it means your photo is over exposed or too bright. But usually the graphics produced by each photo will be different. You can classify them into 3 main forms:
1. Under exposure graph
The graph looks prominent on the left.
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2. Normal graphics
The graph looks balanced in the middle.
3. Over exposure graph
The graph looks prominent on the right.
On average, DSLR or mirrorless digital cameras and even smartphones are now equipped with a histogram. You can use it, for example, when your battery is low and you have to lower the screen brightness so that you have difficulty seeing whether the photo is bright enough, so you can look at this histogram graph.
Good luck!