December 15, 2009 – In July, 2009, I set myself a simple question: What are the limits of HDR processing in suppressing light and bringing out detail? What better test than a night shoot at a brightly lite area? The price of natural gas has prompted a significant amount of drilling in the Barnett Shale running under Fort Worth, and my old connections to the industry suggested an obvious topic, a drill rig. While there are many active in the area, with many different looks, few present good locations for shooting. This rig provided an acceptable location. Hope there’s decent photo angles on the rig that will ultimately be paying me royalty money.
More experience with HDR processing since July made me want to revisit this experiment. I wanted to go back and reshoot this experiment on a night without high clouds, never made it before the rig moved on. So, using the original shots…
Back in July, the initial shoot was 10 exposures in RAW, tripod mounted, 75-300mm IS lens set at 75mm, shooting at f/5, ISO 100, a remote shutter release, a pace timer beeping seconds at me, and an extremely small LED light. I used AE mode to set the first shot, then swapped to full manual, and left everything set as there except time. Exposures were made in 1 EV increments, using shot times running from 0.5 sec to 256 sec (almost black to almost white). I dropped the 2 shots on the extremes after seeing their poor effects on the end results.
Bright lights in night shots usually mean internal reflections, then add in long exposure times and the generated noise. And it did both with these. Back in July each shot was editted individually to clean all that up. In July I then used HDR PhotoStudio for processing, and I couldn’t get the final effects I wanted, prompting this revisit. So this time using those cleaned up images –
Photomatix composited the 8 shots, which I saved prior to applying tone mapping. Did a number of tone mapping experiments before I found something I liked. Those high clouds tended to produce a bright sky until I pulled down both luminosity and highlights. Lots of possibilities, adjustments, experimentation.
Result of the experiment was interesting. At full resolution, ladders going up the back side of the rig are clearly visible, which I couldn’t see standing there. Some of the equipment that was visually blown out standing there, such as the red tank, are rendered acceptably. That said, the highlights still are blown out to a degree, experiments dropping some of the brightest initial exposures did not seem to help much. HDR did bring up the darks very well, with the uncropped image showing considerable detail and appropriate green vegetation in areas where my eyes saw just black.
Shot was cropped for presentation, as presented here in resulting full size (~970kB). The original was an experiment, so was framed with additional area on the right looking at some dark areas and the large broadcast antenna farm south of Dallas. The full resolution uncropped image is here (~2.6MB)
HDR can do many things. I’m not one for some of the wildly colored shots that appear. But this experiment shows that dark detail can be brought up remarkably well, while controlling the highlights can be difficult
