Many people first heard about HDR (High Dynamic Range imaging) when Apple added the feature to iOS. HDR uses sophisticated algorithms to overlay multiple images shot at different shutter speeds to increase the dynamic range of the camera. This helps prevent losing details in a face, for example, when your subject has a bright sky behind it.
Of course, photographers have been doing HDR with more advanced cameras for quite a few years now. Mac users have some excellent high-end programs like Photomatix and HDR EFX Pro with which to post-process their photographs.
There's a low-cost option, HDR Darkroom 3, that does a good job and is very easy to use. It's the latest version of an app that has been evolving for quite some time. At the time of this writing, it's on sale in the Mac App Store for US$14.99. The usual list price is $39.99, so be sure to check if the sale pricing in still in effect.
I gave the latest version a trial run using several landscape photos taken with my Canon 5D. The photos were shot with varying shutter speeds about two stops apart with a fixed ƒ stop. The middle exposure is normally exposed.
Next, the images are loaded into HDR Darkroom 3. There's an option to align the photos, which is helpful if you were shooting hand-held rather than with a tripod. The app can also remove ghosting generated by moving trees or water.
When the images are opened, a range of styles is visible on the right side of the screen. Those styles can be subtle or over the top. There are also two black-and-white presets. Within each style, you can adjust exposure, saturation and vignetting. There are some rudimentary editing tools, like cropping and rotation of images. A handy compare button lets you go back to your original image to see how the HDR image compares with the original. You can easily move from style to style, because nothing is permanent until the photo is saved. There are several export options, and your masterwork can be shared to social media. The app imports almost any photo format, including RAW files.
HDR Darkroom 3 is a very reasonably priced app for those photographers wishing to dabble with HDR. Both Photomatix and HDR EFX Pro are much more powerful and, to my eye, can make a more powerful image, but HDR Darkroom 3 gets you most of the way there for a fraction of the cost. I'd like to see more editing features in the app -- like dust removal or image straightening -- that would let you finish the photo without going to an external editor. You can learn more about the app and see example photos here.
The app requires OS X 10.6 or later and a 64-bit processor.