In photography, the “dynamic range” is the difference between the darkest and lightest tones in an image, generally pure black and pure white. It’s more often used to talk about the maximum dynamic range a camera is capable of.
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Dynamic range is measured in “stops”. An increase of one stop equals a doubling of the brightness level. The human eye can perceive about 20 stops of dynamic range in ideal circumstances. This means that the darkest tones we can perceive at anyone time are about 1,000,000 times darker than the brightest ones in the same scene. This is how you can still see details in dark shadows on a bright, sunny day.
Cameras have a narrower dynamic range than the human eye, although the gap is closing. The best modern cameras like the Nikon D810 can achieve just under 15 stops of dynamic range in any one photo. Most digital cameras get somewhere between 12 and 14 while film negatives can get up to about 13. This is why when you take photos on a sunny day you often have to choose whether you “blow out your highlights”, making them pure white, or “crush your shadows”, making them pure black in the final image.
In this photo I’ve chosen to expose correctly for the highlights. All the shadow detail in the bushes is basically black but the sky is blue.
In this photo I’ve exposed correctly for the shadows. Now you can see the shadow details, but the sky is white.
One problem with talking about dynamic range is that while cameras can capture 14 stops, the best screens can only display about 10 stops. Professionally printed photos get about the same. This means that even though your camera has captured a load of information, there’s no way for you to see it all at once. Instead, you have to make tradeoffs.
Here’s that photo again, except that this time, I’ve edited it so that the dynamic range better matches that of a screen. To do this, I brightened the shadow detail and darkened the highlight detail.
This is pretty close to the limit of what my camera can do. The shadows look pretty good and the sky is definitely blue, but there’s some weird artifacting going on around the clouds. They’re pure white and no amount of work in Photoshop can change that. The transition between them and the sky looks funky because of it.
One method photographers use to overcome dynamic range problems is High Dynamic Range (HDR) photography. In HDR photography, you combine multiple exposures to create a single final image. Below, I’ve combined the two exposures in this article with some HDR software.
As you can see, the sky and bushes are both pretty well exposed, although there is some weird coloring going on, which is one of the chalenges with HDR photography. To read more about how HDR photography works, check our full guide.
Dynamic range is something you’ll run into again and again, whether you’re just comparing cameras, trying to edit a photo so it looks good on screen, or desperately trying to work out how you can capture a scene without losing either shadow or highlight detail.