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Floating Point

A common misconception is that if you work solely in the domain of video you have no need for floating point. But just because your output will ultimately be restricted to the 0.0 to 1.0 range doesn't mean that overbright values above 1.0 won't figure into the images you create.

In the Figures 11.12a, b, and c, each one of the bright Christmas tree lights is getting severely clipped when shown in video space, which is not a problem so long as I'm only displaying the image. In the center image, I followed the rules and converted the image to linear before applying a synthetic motion blur. Indeed, the lights are creating pleasant streaks, but they are not reflecting their true overbright nature. In the third image, I processed the HDR image in floating point, and the lights have a realistic impact on the image as they streak across. Even stretched out across the image, the streaks are still brighter than 1.0. Considering this printed page is not high dynamic range, I think thisexample shows that HDR floating point pixels are a crucial part of making images that simulate the real world through a camera, no matter what the output medium.


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