An important limitation in DSLRs, or in any camera, is the dynamic range of dark shadows to bright highlights which the camera’s sensor can “see”. The human eye can see roughly 20 stops of variance in a given scene. But, the highest-end DSLRs can typically only see about 14 stops of light. So in other words, the human eye can see a wider range of dark shadows to bright light than an individual exposure taken by a camera.
One way to increase the dynamic range of a photograph is to combine multiple exposures, with each exposure increasing (or decreasing) the number of stops. This process, at its most basic level, is typically called “High Dynamic Range” imaging…or HDR. Usually, most cameras are able to take three or five exposure HDR composites, with some cameras able to take as many as 7 or even 9 exposures.
Typically, when I photograph the interior of homes, I take a 3 exposure HDR image, with each shot separated by 2 stops of light. This ensures that I have one underexposed image, one balanced image, and one overexposed shot.
In a three shot HDR composite, the dark image exposes for the brighter areas of the scene (i.e. windows and artificial lights), the overexposed image brings out the darker areas, and the balanced image captures the parts of the scene which are in well-exposed light. Once combined via software, a composite image is created with ideally all areas of the HDR photograph in good exposure.
The following three images are the uncombined individual exposures of a kitchen:
Then, once these three images are combined, we have the resulting HDR composite:
If you want to create an HDR image, here’s a simple guide to follow:
What You Need:
- Obviously you’ll need a camera…preferably one that is capable of auto bracketing exposures. Auto bracketing means the camera will automatically increase and reduce the number of pre-set stops for each individual HDR image taken. Auto-bracketing isn’t a necessary function, but it’s much easier to have the camera handle bracketing automatically, rather than you having to manually adjust the exposure between each image taken.
- A tripod. In order for an HDR image to look right, the individual images must all line up correctly. When you hand-hold a camera, it’s impossible to get multiple individual exposures to be perfectly lined up. That said, there are sophisticated software programs available which can line up three hand-held images for you…but in my experience, using a tripod and creating exposures which match up perfectly will yield the best results.
- HDR blending software. I use Adobe Lightroom most of the time, and also Photomatix on occasion. Lightroom makes combing HDR images easy, since I use it to catalogue and store my library of images anyway. But, in my experience, Photomatix is the most powerful and versatile HDR solution around, and I use it when Lightroom has trouble combining the images.
Keep in mind that it is extremely difficult to create HDR composites out of subjects which require camera movement between the individual exposures. Perfectly still subjects which don’t require camera movement are best suited for HDR photography.
For example, one can capture an HDR image of a waterfall as the subject…because, while the waterfall itself is in motion, one does not need to move the camera at all between individual exposures.
Try and look for scenes with a wide dynamic range…in other words, a scene that has a wide disparity of light emitted between dark areas and bright highlights. Sunrises and sunsets are always good examples of scenes which are conducive to creating HDR composites, as are daylight shots of the interior rooms of a home which has windows.
If your camera allows you to, shoot in RAW format. JPEGs are compressed by the software in your camera which cut down on file size and speed up processing time…but a smaller file size reduces the detail available in the file. RAW files contain the most information possible in the individual exposure…they take up more memory, and take longer for the camera to process…but it’s worth the extra time and space it takes to create RAW files. RAW files are more malleable and conducive to editing than JPEGs. The more detail and information available in each file, the better your resulting HDR composite will look.
Since RAW files take up more space, make sure you have a memory card which is large enough to hold the number of images you’ll be capturing. I always bring along a couple of extra cards in case I shoot more than one card can handle. Also, it’s always a good idea to have a spare card handy in case the one you’re using fails on you.