Ever wonder why photographs you take often don’t capture the vibrancy and detail you saw when you took it? That’s because most camera sensors simply can’t record the wide range of tonal values that your eye can see. The result is photos with areas that appear washed out (overexposed) or murky (underexposed).
High Dynamic Range (HDR) photography is one technique that can be used to address this issue. It does so by using the “best parts” from multiple, bracketed exposures of the same scene. So the blown highlights in the normal exposure are replaced by regions from under-exposed shots where they are not blown out. Likewise, underexposed areas are replaced by the data from the overexposed shot which has preserved some detail in those dark areas. This technique is executed using software such as Photomatix Pro which can be used alone or as a plug-in to other programs such as Adobe Photoshop or Lightroom. The resulting images are highly-detailed and more evenly exposed in all portions of the scene.
It all starts with taking the bracketed exposures. Many cameras, and most DSLRs, allow for automatic exposure bracketing where the camera does a burst of consecutive shots, varying the exposure across the shots. Some cameras can do 7 or more different exposures in just a couple of seconds. The exposure difference can be small, such as a quarter stop, or large, as in a 2-stop bracket; I typically use 5-7 exposures 1 stop apart. Generally you need at least 3 exposures, although one image recorded using RAW format can sometimes yield decent results by adjusting the exposure in post-processing to produce 3 bracketed exposure files from the one photograph. This latter technique can be useful if your subject is moving – separate exposures of a moving subject will likely result in a blurred image which is why HDR techniques are usually reserved for landscapes or other static scenes where movement isn’t pronounced. Ideally a tripod is used to minimize alignment issues.
Once the digital image files have been imported to your computer, you load all the images for a given scene into the HDR software. The software can do some alignment and noise corrections and then displays the image that results from a pre-set effect menu. Most HDR software provides a variety of effects from subtle to bizarre. The artist can start with a base and then modify a number of factors that adjust the strength of the effect, the luminosity of the whole image, or the contrast for elements that are of a certain size. Vignetting can be applied, and overall color/tone can be changed. The adjustments I like best vary depending on the subject, the exposure of the images, and of course the effect I’m trying to achieve for a given work.
If you are interested in trying our HDR, programs like Photomatix offer a trial where you can try it out before buying it.Their site also includes some tutorials that can be helpful in understanding how the program works.
Here’s some example of HDR photographs I’ve taken: