Software for creating HDR images uses some fancy math to merge all three exposure-bracketed photos into a single image that preserves the detail from both the brightest areas of the underexposed image and the darkest areas of the overexposed image:
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Pretty cool, huh? Of course, you wind up with an image that has far more dynamic range than photographic paper or standard LCD monitors are capable of conveying. So most HDR software also goes through a second step called “tone mapping,” which compresses the fused image into a final version that still has a high contrast ratio and color saturation, but also looks good when printed or displayed. (Let me forestall criticism from traditional film photographers right now by acknowledging that certain kinds of film have a very high dynamic range, and that good photographers can deal with huge luminance variations without resorting to software tricks. Just look at Ansel Adams.)
To make the images above, I simply snapped three pictures of the original subject—the foothills of the Green Mountains in Vermont—using the auto exposure bracketing setting on my camera. (The trick here is to hold your camera steady. It’s best to use a tripod.) Then I merged the photos on my Mac using Photomatix Pro, a $99 program made by a small company in France called HDRSoft. There are other standalone programs for making HDR images, including a few free ones, but Photomatix produces the best results, in my experience. If you’re lucky enough to own a recent version of Adobe Photoshop, it has a built-in function called “Merge to HDR” that does the same thing.
Since buying Photomatix, I’ve been going a bit wild with the HDR technique. You can see more of the results by checking out this photoset on Flickr or the slide show at the end of this story. And don’t stop with my images—I’m a rank amateur at this, and to appreciate the full possibilities of HDR photography you should also look at what photographers like Jared Earle are doing (I’m especially struck by this Earle image).
I have to warn you—most of these photos look strange. It’s not that they’re unrealistic, exactly; in point of fact, HDR images are much closer than normal photos to what the human eye can see in real life, given its amazing sensitivity to wide variations in luminance. It’s just that traditional technologies have trained us to expect something very different from a photographic reproduction. We aren’t used to seeing so much detail in both the foreground and the background of a reproduction, and in both the light and the dark areas.
It’s because of all this eye candy vying for your attention that some HDR images almost look staged, as if someone lit the scene with Klieg lights. HDR pictures sometimes remind me
