If you’ve ever taken a shot in sunlight, or any other situation where the brightness range is high, the chances are your camera will have lost some detail in the darkest parts of the picture, the brightest parts or both. It’s one of the most common photography problems you’ll encounter, but it isn’t to do with exposure. It’s because the difference between the brightest and darkest areas, or ‘dynamic range’, is so great that you can’t find a single exposure that can capture them both.
Digital camera sensors can capture a wide range of brightness values, but there is a limit. If you’re faced with a scene that has a wider dynamic range (or brightness range) than the camera’s, you may well have a problem. In this article we’ll offer some of our best camera tips and expert advice for recognising, measuring and overcoming this problem.
How do you check dynamic range?
Your camera’s histogram display is a good way to check if there’s a problem (learn more about how to read a histogram).
If the histogram is chopped off, or ‘clipped’ at the left-hand end of the scale, it means that some of the darkest parts of the picture haven’t recorded and will appear as a solid black.
If the histogram is chopped of at the right-hand end, it means the brightest parts of the picture have been overexposed and will reproduce as a solid white.
Quite often, you can adjust the exposure, re-shoot and solve the problem. But scenes with a very wide brightness range also produce a very wide histogram – and sometimes the histogram is so wide that it’s clipped at one end or the other, no matter how you adjust the exposure.
The range of tones on an overcast day is quite narrow, producing a narrow histogram. This won’t pose any exposure problems. But the extreme brightness range of a sunny day may produce a histogram so wide that it won’t fit within the camera’s dynamic range no matter what you do.
What’s the answer?
The histogram shows you the range of tones in the whole picture, but not necessarily the ones which you’re most interested in! Sometimes it’s okay to have dense areas of black. It’s fine, for example, in black and white photography.
So by all means use the histogram as a guide, but consider checking key areas of the picture yourself. You can do this using your camera’s spot metering mode to check the brightest and darkest key areas in the picture to see if there’s a single exposure which can capture them both.
Alternatively, you can shoot raw files. These capture up to 1EV of extra shadow and highlight detail that you can extract later in your raw conversion software. You won’t see any sign of this on the camera histogram, though, because your camera will display a processed JPEG preview of your image for display on the LCD, even if you’ve shot in the raw format.
You still have to get the exposure exactly right, even if you shoot raw, but the slight extra leeway might be all you need to capture extremely dark and bright tones in the image.
Sometimes, though, even shooting raw files won’t be enough, and this is where you enter the world of HDR…