Dynamic range is the camera sensor’s ability to capture detail in very bright and very dark parts of a scene. Cameras (or sensors) with a low dynamic range record dark shadows as a solid black or bright highlights as a featureless white. In the days of film, this was known as a film’s ‘exposure latitude’.
Dynamic range isn’t a problem in every shot. Low contrast scenes with flat lighting have a low dynamic range that any camera sensor can easily cope with and the exposure is not particularly critical because there’s no risk of losing shadow or highlight detail (hence the idea of ‘exposure latitude’). But sunlit scenes and especially backlit subjects can have a much higher contrast range.
It is possible to measure the dynamic range of sensors, and the results are usually quoted as EV (exposure value) numbers or, to use the old term, as ‘stops’. A simple point and shoot camera that captures only JPEG images might have a dynamic range of 9 or 10 stops. A DSLR or a mirrorless camera with a larger sensor that’s used to capture RAW files might have a dynamic range of 12-13 stops. A high-end medium format camera might be able to capture a 15-stop dynamic range.
Many everyday scenes have a dynamic range of just a few stops (EV) so they don’t pose a problem. Some scenes, however, may have a much higher dynamic range that’s outside the capabilities of even the best sensor.
This is where you have to be very careful with exposure. If the dynamic range of the scene is the same as your camera sensor’s, you have no exposure latitude at all, and you have to get the exposure exactly right. Often, it will be higher still, and you have to accept an exposure that will sacrifice either extreme shadow or highlight detail, simply because the camera’s dynamic range is not wide enough to capture both.
You can see this in the image histogram. Where the scene’s dynamic range is higher than the camera can record, either the shadows (at the left end of the histogram) or the highlights (at the right end) will be ‘clipped’.
RAW files have an advantage here. They store extended brightness information compared to JPEG images, and you can use RAW processing software for a degree of highlight recovery or shadow recovery not possible with JPEGs.
Some cameras, notably from Fujifilm, offer dynamic range expansion modes. These reduce the exposure to make sure highlight detail isn’t clipped, then increase the signal processing to bring up dark shadow details and restore normal looking midtone brightness. Fujifilm cameras offer a dynamic range expansion of 200% or 400% (1EV or 2EV)
The other issue with high dynamic range scenes is that even if the camera can capture the full range of tones, the shadows and highlights are too dark or too bright, respectively, to be able to see much. Some makers off in-camera shadow/highlight compensation which uses exposure adjustments and shadow boosting techniques. Nikon’s Active D-Lighting system works in this way – the Active refers to the exposure adjustment that makes sure highlight detail isn’t lost, and the D-Lighting is the shadow adjustment that stops images looking too dark.
For ultra high contrast scenes such as cities at night or backlit sunsets, many photographers turn to HDR photography, where you capture the same scene with a series of different exposures and then merge them in HDR software. Some cameras have in-built HDR modes which merge exposures automatically, though with less control.