HDR: High Dynamic Range

Review:
I'm often asked about why some of my shots look so different, or more like paintings than photographs, and also how I managed to pull 'em off. It has a lot to do with my post-processing, and I do plan to detail out, step by step, how I've edited one of my images sometime in the future. But for now, here's a basic overview of a process that I think is pretty damn cool -- HDR (High Dynamic Range).



What is HDR?

HDR, or High Dynamic Range, is a method of obtaining a photo with a greater dynamic range of luminance than a normal camera allows. That is to say, capturing a higher range of exposure between what you see in dark shadows and what you see in bright highlights. When shooting film, the acceptable rage of exposure between these points is referred to as "latitude."

The most common method of HDR photography is combining multiple exposures from a normal camera. Note: the term "normal" is always relative and a higher dynamic range than now may be the norm of tomorrow as High Dynamic Range cameras find their way to the public. As of now, most cameras capture about a solid 3-4 stop range of luminance within a single 16bit RAW file.




It works like this: you take different exposures of the same shot and combine them together giving you an increase in shadow and highlight detail.

You need to bracket multiple shots with varying exposure values. For example, I often set my camera on a tripod (to minimize change in angle within the frame), adjust my f-stop (locking aperture and depth of field), adjust and lock my focus (again, maintaining depth of field and also focal distance), and then shoot different exposures (only changing the shutter-speed) of the exact same frame.



I usually shoot one properly exposed shot at 0 ev, one +2 ev (over exposed -2 stops) and one -2 ev (under exposed +2 stops). Some cameras allow for easy exposure bracketing with 3 to sometimes 5 exposure value settings. Setting your camera to Aperture Priority mode and manual focus helps. I also recommend a sturdy tripod, a shutter trigger, and enabling mirror lockup to help minimize camera shake. You should also set your camera to auto fire if it has the option. This can also be accomplished with point and shoot cameras but is a lot more work. I've shot many hand-held HDRs too, but I've sometimes needed to align them individually in post which can be quite a chore.




After you have your multiple exposures, you take the photos to an imaging program and work from there. Photoshop CS3 and higher allow HDR merging (CS5 trial is now available here), but the most popular tool today is Photomatix (free trial here) which combines tonemapping and a load of imaging options to allow everything from a more natural look to a very surreal dream-like look. Style is subjective, so do what you like, but try not to go too overboard playing with sliders and settings. You'll end up with halos around everything, over sharpening, and over-saturated colors that could send your viewers into Epileptic seizures.

That's about it. Here's a fantastic tutorial with nice visuals by a guy who is one of the best at the technique, Trey Ratcliff (Stuck in Customs HDR tute here).