You hear the word histogram tossed around all the time when reading about photography. For professional photographers, the term is a household word—and there’s a good reason for that. Knowing how to read and use the histogram on your camera will help you make the leap from auto to manual mode and still be able to take properly exposed photos. Take a look as John Greengo explains the mysterious tool and teaches us why it’s so important to know:
What Is a Histogram?
As Greengo explains, a histogram is essentially a graph of the tonal distribution of a photograph. It tells you the tonal quality of the darks, shadows, mid-tones, and highlights by displaying whether they are over-, under-, or properly exposed. When looking at the histrogram chart on your camera, these values are read from left to right, with the far left side of the histrogram representing the darks and working its way through shadows, mid-tones, and highlights, which are on the far right side of the chart.
How to Read a Histogram
Now that you understand how the histogram is laid out, reading it should be fairly easy for you. Depending on how the historgram spikes or dips, you should be able to tell exactly how the image is exposed. For example, let’s look at these three exposures of a tiger and compare their histograms:
The correctly exposed image has a histogram that is balanced nicely in the mid-tones, with a slight weight toward the shadows. This histogram tells us the mid-tones have a lot of pixel values and a nice exposure, whereas the extreme darks and highlights have no pixel values, signifying that the image is neither irrecoverably dark nor does it have blown-out highlights.
Comparing the over-exposed and under-exposed frames, it’s easy to conclude what “bad” darks and highlights will look like on your histogram. If your histogram is heavily pushed toward one side of the chart, chances are you don’t have the exposure you need. Try adjusting either you ISO, aperture, or shutter speed to either decrease or increase the exposure until everything meets back up near the middle.
“Generally, what you want is a mountain in the middle, and you don’t want it stacked up on either the left or right side. I would have to say that you probably want to be most careful of things that are stacked up on the right side. If you have blown out pixels, they are generally very, very bad.” –John Greengo
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