Photographer John Greengo gives a simple explanation of that color graph on your camera’s display known as a histogram as part of his instructional course for CreativeLive. The tutorial breaks down what the feature does and why it’s an important part of taking better photos.
It breaks up the entire scene into individual pixels. It forgets about color, it’s just about tonality. If you can imagine a black pixel and white pixel and a whole bunch more gray pixels of slightly different tonality. And then we’re going to organize this. We’re going to put the black pixel on the left, the white one on the right and all the pixels of equal tonality lined up in a column. And with this, we have a histogram.