Using a Histogram in the Field
Do you refer to the histogram on your camera when you are out shooting?
Do you know how to interpret the results that are shown
in a histogram? If not, here is a quick tutorial!
What is a Histogram?
A histogram is a graphic depiction of the tonal values in your photograph, organized in 256 columns, based on brightness. Black tones (0% brightness) are displayed on the left, and white tones (100% brightness) are displayed on the right. The mid-tones are arranged in the middle of the histogram, based on their brightness.
In a well-exposed photograph, there are very few if any 100% black or white tones, which means that there is no loss of data and shadows and highlights can be recovered in post-processing. If a portion of the tonal values are “touching” either edge of the histogram, that indicates a loss of detail (data), which is also called “clipping”. Loss of highlight detail – meaning that the area is completely white – is known as Highlight Clipping and appears on the right side of the histogram. Loss of shadow detail – meaning that the area is completely black with no detail – is known as Shadow Clipping and appears on the left side of the histogram.
Usually either of the instances of clipping can be corrected by changing exposure settings, but in some cases, like an image with the sun in it, will have some highlight clipping simply because the sun is so bright.
How do you use a Histogram?
In general, you can use the histogram to evaluate the exposure of a photograph, but there are some exceptions to this rule. For instance, if you are photographing an image that has a lot of white tones, then the histogram will be shifted mostly to the right. If the exposure settings are adjusted to represent a “good histogram”, the photo would be underexposed.
Some photographers routinely check the histogram for each shot they take. Some never refer to the histogram. Whether you regularly use the histogram or only occasionally check it, learning how to read a histogram can be invaluable for those times when using a histogram can be beneficial to nailing the shot.