Sunday, July 12, 2009

HDR Railroad Car


My family and I where in Scranton over the 4th of July weekend visiting my wife's parents. I decided to go down to "Steamtown National Historic Site" to take some photographs. When I told my wife where I was going she asked "How many photographs of trains do you need?" Her question was not without merit, I have photographed there many times, the decaying engines and rolling stock offer limitless photographic possibilities and are ideal subjects for trying out new equipment and techniques. This time I wanted to try the HDR (high density range)feature in Photoshop, and I knew the interior of a railroad car would be an excellent test subject as it would contain both murky shadows and bright highlights.

HDR merges multiple exposures of the same scene into one image with an expanded tonal range. Using my cameras auto exposure bracketing feature, I was able to make three exposures in rapid succession. The first exposure would be two stops underexposed, the second, properly exposed and the third, two stops overexposed. The idea being that when merged, the extra shadow detail from the overexposed frame and the added highlight detail from the underexposed frame combined with the normally exposed frame would yield an image with a tonal range that would not be possible in a single capture.

While it is possible to hand hold the camera and let Photoshop try to align the exposures it's better to use a tripod for HDR.

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