How to Read A Histogram in Photography

When you first hear other photographers talking of histograms, it may take you back to high school Statistics class – something you did not anticipate when deciding to follow your artistic passion – but there’s no need to be intimidated by them or hesitate to use them as a tool. If you want to learn how to read a histogram in photography, you’ve come to the right spot! Reading and understanding histograms is fairly simple, once you’ve learned what it all means, and they can be used to help you fine-tune the exposure and color of your photographs.

What is A Histogram?

Histograms are approximate visual representations of distribution. They are composed of a number of rectangles, which represent ranges of data, and look very similar to bar graphs, except for the fact that there are no gaps between the rectangles. Histograms are used to represent everything from weather patterns to stocks to, of course, light in photography.

How are Histograms Used in Photography?

In photography, histograms are used to represent light levels. It shows you the distribution of tones (brightness and darkness) in a photograph, and many can also show the distribution of color. You can view your histograms on your camera’s LCD or in Lightroom while editing.

How to Read A Histogram

Photography histograms typically have 256 rectangular bars, to represent the tonalities of an 8-bit image, but they may almost appear to blend together into a smooth curve. The left side of the histogram represents black, and the right side of the histogram represents white. In most images, there should only be peaks in the curve in the middle of the histogram, and it should taper off towards both the black and white ends. The distribution throughout the middle of the curve will vary depending on the image, and some images may not even taper off, although these images are certainly outliers.

How to Use Histograms in Your Photography

The histogram is not by any means the only tool, or even the most important tool, to guide lighting choices in your photography, but it can be a useful indicator. Checking the histogram on your camera occasionally, especially when the lighting you’re working with is unusual or complicated, can give you a good idea of whether your exposure is correct or not. A roughly centered histogram is, in most cases, a good sign.

What Does A Histogram for Correct Exposure Look Like?

A “correctly” exposed image can produce many different shapes of a histogram. The curve in the center may have one peak or many, which may be directly halfway between the edges or skewed slightly toward one side. More important, and less likely to vary if the exposure is correct, are the edges of the histogram.

The tapering off mentioned earlier is what tells you that your exposure is roughly correct; if either end of the histogram does not taper, it may indicate a problem with the exposure. A histogram that “collides” with the left side of the graph usually indicates an underexposed image, while one that “collides” with the right side indicates an overexposed one.

What Does A Histogram for Normal Contrast Look Like?

You can also determine whether an image’s contrast is low, average, or high by looking at the histogram. An image with lower contrast will have the peak or peaks of the curve gathered closely in the center, while one with higher contrast will have peaks distributed more widely throughout the graph (although the ends will still taper off). An image with typical or average contrast will have something in between, with peaks or high values on the histogram spread out somewhat, but not over the entire length of the graph.

What are “Low Key” and “High Key” Images?

The term “low key” refers to an image that has more dark tones than normal. It’s not incorrect (as long as it’s intentional), but the histogram for dark, low-key images will look different from normal ones. They will be skewed heavily toward the left, in some cases even colliding with the left wall, but more likely with a main peak that is very close to the left side.

“High key” images are the opposite; they have more light tones than normal, and their histograms are skewed toward the right. They may collide with the right wall or have peaks and high values close to the right side of the graph.

Conclusion

Although histograms may seem more like science than art, you should remember that there’s no exact right or wrong to them. A histogram can provide you with important information about the light levels in an image, but the details and the shape of the histogram will vary depending on a lot of other factors, but you should not rely too heavily on them. As you continue your education experience as a photographer and editor, histograms and other tools like them will become simple things that allow you to adjust images to your own personal preferences.

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