Using your camera’s histogram screens will guarantee you a much higher percentage of well-exposed images. It is well worth spending time to understand the histogram. It’s not as complicated as it may look at first.
I’ll try to cover this feature with enough detail to give you a working knowledge of how to use the histogram to make better pictures. If you are deeply interested in the histogram, there is a lot of research material available on the Nikonians forums and on the Internet. Although this overview is brief, it will present enough knowledge to improve your technique immediately.
The camera’s sensor can only record a certain range of light values—about 5 to 7 usable EV steps. Unfortunately, many of the higher-contrast subjects we shoot can contain over 12 stops of light values. This is quite a bit more than it is possible to capture in a single exposure. It’s important to understand how your camera records light so that you can better control how the image is captured.
Look at figure 1 closely. The gray rectangular area represents an in-camera histogram. Examine it carefully! Think about it for a minute before reading on.
The histogram is basically a graph that represents the maximum range of light values your camera can capture, in 256 steps (0 = pure black, and 255 = pure white). In the middle of the histogram are the mid-range values that represent middle colors like grays, light browns, and greens. The values from just above zero and just below 255 contain detail.
The actual histogram graph looks like a mountain peak, or a series of peaks, and the more there is of a particular color, the taller the peak. In some cases the graph will be rounder on top, and in other cases it will be flattened.
The left side of the histogram represents the maximum dark values that your camera can record. The right side represents the maximum brightness values your camera can capture. On either end of the histogram the light values contain no detail. They are either completely black or completely white.
The height of the histogram (top of mountain peaks) represents the amount of individual colors. You cannot easily control this value in-camera, other than changing to a Picture Control with more or less saturated color, so it is for your information only.
We are mostly concerned with the left- and right-side values of the histogram, since we do have much greater control over those (dark vs. light).
Simply put, the histogram’s left and right directions are related to the darkness and lightness of the image, while the up and down directions of the histogram (valleys and peaks) have to do with the amount of color information. I repeated this for emphasis!
The left (dark) and right (light) directions are very important for your picture taking. If the image is too dark, the histogram will show that by clipping off the light values on the left; or if it’s too light, by clipping on the right. This will become easier to understand as we look at well-exposed and poorly exposed images. Check out the Histogram Basic Tutorial in figure 2 below, and then we’ll look at things in more detail.
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