Dynamic range and RAW file "bit depth"

Started Jan 25, 2014 | Questions thread
DSPographer Senior Member • Posts: 2,464
Re: of course there are reasons not to record 17 bits

RussellInCincinnati wrote:

RussellInCincinnati wrote: Come to think of it, it wouldn't be skin off of anyone's back to just have a menu option for 17 bit-depth raw files. Totally linear recording of produced-electron counts. Yes you'd be encoding a ton of noise in the least significant bits, slowing down file write times since the numbers written would be less-losslessly-compressible, etc.

DSPographer wrote: This isn't just wasteful of file bits, it also could significantly slow down the raw converter. In column parallel ramp converters like Sony's Exmor sensors use, having a nonlinear ramp dramatically speeds up the conversion process. So, on many cameras that have "14-bit" raw capability the conversion step size is not really uniform, instead it increases approximately as the square root of the level, so that the time to perform the ramp conversion is not excessive.

OK, so there are at least 4 reasons why people wouldn't want 17-bit-deep raw file data, instead of merely 3 drawbacks. It just wouldn't hurt anyone to offer the option. Just like my browser offers me a really tiny default font-size on its menu of typeface sizes, even though we can think of many reasons not to use such a tiny font.

Well, 17 bits is a really odd size. If I had to choose one number format that would exceed any sensors capability it would probably be a 16 bit floating point like IEEE 754 binary16. I would also at least losslessly compress the raw files.

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