Saturday, April 01, 2006

Flickr HDR

Do you wonder What's the deal with HDR? The issue with high dynamic range photography boils down to trying cram the huge range of brightness you find in the real world down to the 256 levels of brightness supported by jpeg files. HDR is about getting beyond this limitation.

The amount of light in a pixel reflecting off a cricket in the shade might a millionth of what's reflecting off a white sail flapping in the summer sun. Mapping a huge range of brightness into a small range often doesn't work very well--either the shadows wind up pitch black or the highlights become pure white. Given such a range of intensity, details in the shadows or highlights invariably get chopped off; there's no other option given the technology, something's gotta go. This is why you can hardly make out faces when you take a picture of people standing in front of a window exposing a bright sky in the background.

Using RAW, which supports more levels helps, but many people are taking multiple exposures to capture shadows and highlights separately and ultimately merging them back together to get results free of clipping at the low and high ends of the range.

Following is a shot from Flickr's Quality HDR group by Tycho Moon. It's an interesting group worth checking out if you're interested and new to this sort of thing.

(ht: Raw Format)


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