Tuesday, April 22, 2008

Size Does Matter - Here's the Proof

Sure RAW is king of the hill when it comes to recovering blown out highlights. We've known that for years, but nobody even wanted to consider the lowly Jpeg's capabilities for highlight recovery - until now, right here on DigitalProTalk, so here we go.

But first to get a little background on dynamic range and CMOS sensors, I'd like you to read Xinqiao Liu's PHD dissertation on, "CMOS IMAGE SENSORS DYNAMIC RANGE AND SNR ENHANCEMENT VIA STATISTICAL SIGNAL PROCESSING" right here . It's only 139 pages long.

OK, just kidding, but you need to know that all the chips in all the cameras out there have differing amounts of dynamic range inherent in their design. This is another way of saying that some cameras do better than others in capturing the highlights without blowing them out. Why is that - it's about the size of the photo receptor - our friend the pixel. A bigger photo receptor, means more light (photons) can enter the photo site during the exposure, and the greater number of photons relative to the inherent noise associated with the CMOS sensor means a higher Signal to Noise ratio - read, higher dynamic range.

You can read a fascinating article on the subject and a lot more on Canon's site right here. Sony's echoes the same claim here for larger pixels. Nikon has a easy to understand article on the dynamic range right here. Armed with this new knowledge, let's see just how far we can push the pixels around in today's video tutorial entitled, "JPEG Showdown - Saving the Pixels" in the next post.

1 comment:

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