Of HDR and Waterfalls
Flowing water is one of the few moving subjects which lends itself to the HDR software magic.
HDR of Hidden Falls – Big Woods State Park, MN
HDR, or High-Dynamic-Range, processing depends upon having multiple exposures of a scene taken at different EV values to retain all of the highlight and all of the shadow details present in the scene. Naturally, any object moving in the scene between exposures will render poorly resulting in ghosting on your final XDR image. This applies to almost all moving objects within a scene.
Devil’s Tower with clouds showing movement in HDR processing
Aesthetically, this creates poorly accepted images-with a couple of notable exceptions. Clouds can move within the bracketed exposures and still come out looking ok. This shot of Devil’s tower combines three exposures where clouds were moving across the scene rather quickly. The resulting shot, while not entirely natural, is pleasing none-the-less. Another item that can move between exposures and still look amazing is flowing water-particularly in a waterfall.
Consider the following three images used to construct the HDR image featured at the beginning of the article:
The only thing different about each exposure was the shutter speeds which were 1/4, 1/15 and 1.0 seconds respectively. Thus, the water has a markedly different appearance in each image. The darkest image shows the detail of the water and the lightest the flow of the water over time. When combined and interpolated in an HDR software package (Photomatix in this case), the effect creates an almost cinematic shimmering in the final water’s image.
It was a most unexpected result at the time but one that I have used to advantage many times since with both faster and slower exposure ranges. Unlike the surrealistic rendering of the clouds in the Devil’s tower shot, the waterfall exhibits a much more life-like sheen. It was almost like being there.
Waterfalls love HDR-not only because of the shadow and highlight detail retention-but also because the varying exposure times create some interesting and unexpected effects.
Rikk Flohr © 2009
