The histogram is one of the most useful tools in the camera that helps to evaluate proper exposure and is also one of the least understood and used tools. If you want to become a better photographer, you need to understand how the histogram works and use it to nail exposures. It is the best way to make sure that you are properly exposing the frame you are photographing.
Understanding light is one of the keys to being a good photographer and understanding your histogram is a core skill in assessing available light. When you are ready to tackle the broader skill of getting amazingly exposed images, then you will want to take a look at the Understanding Light guide here.
Note to remember: Nothing can evaluate exposure better than your eyes, but then there are situations when the light is harsh or very limited, that you need some help evaluating exposure and you can use the histogram as a guide.
So, what is a histogram? Ahistogram is a graphical representation of the tonal values in a photograph (between 0 and 255) and is an accurate guide to exposure.
And what does it represent? It is a curve that represents tones and pixels in the image. The x-axis represents the tonal variations from black to white; that is, blacks, shadows, midtones, highlights and whites. The y-axis represents the amount of pixels for a given tonal value or range.
Here is a representation of the information you find on the histogram. Included here is only the luminosity histogram, but it is good to look at the RGB colours which we will look at in a different article.