On Dec 12, 2006, at 1:20 PM, Cory Papenfuss wrote: >> RAW format has always been what was written from the sensor into a >> digital representation, a 2D array of photosite values along with >> metadata describing the camera state and organization of that array, >> no matter what transformations or A-D conversion methodology has >> been. >> > Right. It isn't anymore unless the RAW file has 22-bits of data > per photosite. > > If it's 22-bits truncated to the 12 most-significant bits, > there's no reason for 22-bits to begin with. One would expect that > the > "most relevant" 12-bits of dynamic range would be chosen to > truncate into > the 12 for a RAW file. The "most relevant" is the part that could > be new. > > With previous cameras with 12-bit A/D's, one could be reasonably > certain that ALL data captured was recorded in the file. That is no > longer the case.
Thats not true. Nikon and Canon both do a lot of their own sensor to digital representation processing too, ya know? And their RAW data is just as much RAW as anyone else's. I don't know what quantization they use in their A-D converter; I suspect it's greater than 12 bits at least in the higher end cameras ... I suspect 14 or 16 bit, it would have to be if they're concerned with round-off error in modeling the voltages for a good 12 bit representation. Pentax has gone beyond that with a 22 bit A-D, which makes much more accurate 12 bit output. 22 bit quantization vs other cameras' 12, 14 or 16 bit quantization renders better modeling of the voltages regardless of whether the output digital representation is further reduced to 12 bit or not. I don't presume to know what Pentax did in tuning the A->D converter and subsequent 22->12 bit transformation, but whatever the body writes to the RAW format file as sensor date is, by definition, the camera's RAW format data. You can't get at or use anything more anyway so there's no point in debating it. Godfrey -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net
