Thursday, May 12, 2011

PhotoProject :: HDR looking towards the sun

2011-05-14After three very wintery days of constant rain, strong winds and bland low grey skys. Not an inducement outside to take pictures. Today the blue sky peaked through late in the day, so I headed down the beach, to find a real gale force headwind. I figured I might get a few of those great moments when the suns rays radiate out from behind a cloud. The sort of thing Turner would love to paint, but happening at a fast and furious pace. The problem is that when  you point your camera towards the sun, you pretty well always give you a very high contrast image, a situation that your camera’s light meter will have a lot of trouble making the right decision. I do know that you will possibly be ok if you wait till a cloud covers the sun and only the darker zones will be black and the sky or sun will not be bleached out. (See the EV=0 exposure in the set above). I also know that a bracketed set at different EV setting is a very easy way to hedge your bets and quickly get a range of exposures “just in chance”. Further that set of bracketed images can be used for HDRi technique. This allows you to slightly expand the dynamic range of the image to put a little in the shadows or fill in a bleached sky. So the fleeting moments in the weather gave me a great little photoproject to test the suitability of using HDRI to refine a very contrasty situation.
Picturenaut Tone Mapping screenFor this test I have used Picturenaut with everything set to automatic. In particular I have used auto contrast during tone mapping. I have found that contrast is the most sensitive setting when you do any HDRI work. The next trap for occasional users is the saturation slider, which tends to produce very surreal lighting (so that was also left at whatever the tone mapping set). The three tone mapping strategies in Picturenaut I like are either exposure, Adaptive logarithm or Photo Receptor Tone mappings and I felt I needed to see how each performed on it own (ie automatically).
Clearly all the HDRI images are nice, and look natural compared with the straight image at a standard exposure. All that was needed was a bit of croping and straightening. It is not clear that there is a massive difference but I can tell there is subtly in tonal range. Was the extra processing worth it? The results are here for you to judge.
Original exposure - Sun through the clouds HDRi - Exposure Tone Mapping HDRi- Adaptive Log Tone MappingHDRi - Photo Receptor Tone MappingOriginal Exposure - The storm arrives HDRi - Exposure Tone Mappinghdri sunset cloud logHDRi - Photo Receptor Tone Mapping
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