| Sunday, June 24, 2007 |
01:56 - Unpatentable idea #41227
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Wouldn't it be cool if there were such a thing as a photographic file format where, rather than storing 0/0/0 as pure black and (say) 255/255/255 as pure white, it actually defined black to be somewhere around 30 and white around 225?
That way, if you're taking a photo and you underexpose or overexpose it, rather than railing most of the histogram of colors into the 0 or 255 values, it would have some overrun room on either end, where it could store color values that go beyond the normal range of the exposure. For instance, if I were to take an overexposed shot of something white against a light gray background, the resulting picture would still look totally white, but the image file would still store the white object as whiter than white, as it were, and the object and the background would still have distinctly different color values in the storage medium. The background would be stored as "white", but the object would be somewhere up in the "beyond white" zone. The upshot of this would be that you could then post-process the file and recover a lot of the color detail that would otherwise have been lost if everything had gotten flattened against the "white" end of the spectrum (or black, as the case may be).
... Actually this would probably only work for overexposure, not underexposure, because if there isn't enough light to trip the sensor, there isn't enough light to trip the sensor (well, unless the sensitivity is being artificially decreased in software by bracketing or something). But there's nothing stopping the sensor from recording more light than the human eye normally registers as "white", right? So why not store that distinction in a reserved buffer zone so as to make post-processing potentially more fruitful? It's a bit less color space for actual imagery, true, but the benefits might outweigh the cost.
Okay: now here's the part where everyone tells me that this has already been done, and either a) is unfeasible for a variety of very cogent reasons, or b) is already the way it's done across the board in industry-standard mechanisms. Have at it!
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Brian Tiemann
