Hi Guys....ok....so usually once we get to the point where we are trying to differentiate between a monkey on a typewriter and a marketing VP with a dartboard, the thread ends.....and rightfully so.....but I have found this very interesting and wanted to bump the thread as this has started to make some sense to me....

This thread has reminded me of some comments Daniel made awhile ago about how Canon should decrease file size with increasing ISO as some of the data was becoming useless (feel free to correct me if I am off) and dynamic range was decreasing. This thread is helping me understand what may have been meant by that statement. What I am trying to wrap my head around is how ISO works and the relationship between ISO and dynamic range.

I do work a (very) little with electronic parts and analog signals. Our devices have a typical analog signal from 4 to 20 mA (I assume that the sensors report a different range and, maybe, units). So, is what you are saying that each pixel reports an analog signal within the range (say 4 mA) and when the camera is set at ISO 100, it uses 4 mA to represent the intensity of that pixel in generating the image? Then, for ISO 200 it doubles the 4 mA signal output and uses 8 mA to generate the image, etc? In that event, the dynamic range associated with an output at the top of the range is lost. Correct?

Is this what you mean by adjusting analog gain? If so, it is pretty easy to see how the DR would become limited. I know I am only using 4 to 20 mA because that is what I am familiar, but if the dynamic range is equivalent to the analog output at ISO 100, then wouldn't the top half of the data be lost with every stop gained by adjusting ISO? That is an awful lot, so I suspect the relationship between analog output and DR isn't linear. Is this off-base? If so, could someone elaborate on the relationship between the analog output and DR?

Of course, after I understand that, the next questions are what is stored in a RAW file if it isn't the analog output and what is meant by "pushing RAW?" Quick guess is that we are going from analog scale (similar to the 4-20 mA) which would be limited by the sensitivity of the device to a digital scale (somewhat limitless).....but this is why am asking the question.
Thanks,
Brant