HDR

Once again … it’s raining here in the Susquehanna Valley. However it was clear yesterday and we seized the opportunity to take a ride along the rail trail on our tandem bike. We did an out-n-back. With a few stops for photos, and one for chocolate, the 22 miles took just over two hours. On the return trip we stopped at a pretty little rivulet. Because I was afraid to bring the DSLR on such a trip I had the Sony Hx9V with me. Although the battery was running low I thought I might have just enough power to shoot a few HDR sequences. HDR stands for High Dynamic Range. HDR manipulations are done using computer software which will take advantage of bracketed images captured by your digital camera. Imagine a scene containing different types of illumination. In addition to well-lit areas, some are very bright while others are very dark. If you were to take a photo of this scene the well-lit areas would turn out nicely but the dark areas would be underexposed and the light areas would be overexposed – details, in both the very light and the very dark, will be lost. To get around this problem you can take a photo that is underexposed (this will bring out detail in the brightly lit areas), another that is overexposed (this will bring out detail in the dark areas), and another that is properly exposed (this will allow well-lit areas to be properly recorded). Now, imagine a piece of computer software that is able to generate a fourth, composite, image comprised of all of the properly exposed bits of the three original pictures. This is what HDR software packages such as Photomatix do. The scene below lent itself well to this technique. The wood in the background was very brightly illuminated while the little waterfall was quite dark. The Hx9V took three images in rapid succession, one under, one over, and one at the correct exposure. Once these were downloaded to the computer, Photomatix generated the final image which is shown below. Although I like its overall feel I do not like the look of the flowing water. Remember that this image is a composite of three taken tenths of seconds apart. Although there are HDR techniques which may lessen the influence of moving subjects, these don’t do much for water. On the other hand if I had used a slower shutter this would have caused a more uniform blur. If I had selected a more rapid shutter this would have stopped the flow all together. Because I was in a bit of a rush I elected to let the camera choose the shutter speed. Anyway, I hope you enjoy the result.

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