According to The Magic of Digital Nature Photography by Robert Sheppard, the histogram is a "graph of the tonalities that your sensor records from the scene" (Sheppard, 51). It is a better interpretation of the exposure of your photographs than the LCD monitor. The left side of the histogram represents the shadows and the amount of black in the scene, while the right side represents the highlights and the amount of white in the scene.
There are certain details you can look out for when you are looking as to whether your photograph is properly exposed or not. When there is a gap or cliff at the right side of the histogram, then the exposure isn't completely optimal. When you look for a gap or a cliff enough times, then it becomes instinctive, and allows you to use the histogram to look out for certain things:
1.) Clipping - "if a histogram hill stops at a steep cliff at the right side, detail is clipped. This means there are additional tones and colors that could be captured, but are not because the detail is 'clipped' off" (Sheppard, 52). When this happens, you have reached your sensor's capacities and highlights are blown out.
2.) Gaps - you want to avoid gaps on the right side of the photograph because it shows that you have gaps in the tonal details of the photograph.
3.) Tonalities - It's important to watch where main tonalities fall because you don't want all of the tonalities in dark subjects to fall on the left side of the histogram. It would give less "noise" and better color if you add exposure to the photograph. You can increase exposure by adjusting aperture and shutter speed, which I will talk about in a different blog post.
Now, here are some examples of proper and improper exposure:
This picture was taken when doing a fall photo shoot with my friend, Carissa. When evaluating the histogram for the photograph, I saw that the photograph was underexposed, because the bulk of the graph is more towards the left side and the hill on the right side doesn't gradually decrease. If it would have proper exposure, then the hill would be towards the center and the cliff on the right side wouldn't be there. When we look back at the photograph, we can see that the leaves of the tree are dark, which can give a hint that there could be an exposure problem.
An example of proper exposure is the photograph of my friend, Carissa, swinging with trees in the background. When looking at the histogram, the hill is in the center, which tells us that the light is more evenly distributed, rather than the light or darkness going towards one side of the photograph. When we look back to the photograph, we can see that there aren't any areas where it is too dark, but there aren't any parts where the sun is blinding anything.
To wrap this up, have you ever used the histogram before? What are some tips that you have to create proper exposure for a good histogram?
Works Cited: Sheppard, Rob. The Magic of Digital Nature Photography. New York: Lark, 2007. Print.
