I believe that there is an analog portion to the circuitry before it gets to the A/D converter. And this analog portion includes a programmable amplifier. So the A/D is always giving you all the bits, its just that at higher amplifications for higher ISO, the noise factor is much higher.
On Wed, May 18, 2016 at 2:03 PM, John <sesso...@earthlink.net> wrote: > I'm pretty sure you're over-thinking this. > > > On 5/18/2016 2:37 PM, Larry Colen wrote: >> >> I expect that the answer to this question is "Yes, but it makes no >> practical difference". >> >> Let's say a camera has a 12 bit D/A and at base ISO of 100 has 10 stops >> of dynamic range. In theory the chart would look something like this: >> >> DR ISO >> __ _________ >> 10 100 >> 09 200 >> 08 400 >> 07 800 >> 06 1600 >> 05 3200 >> 04 6400 >> 03 12800 >> 02 25600 >> 01 51200 >> >> Lets say that you are doing a macro photo of a grey card. It's lit from >> the side, to show some texture, so you end up with 3 stops of DR coming >> off the card. Lets's also assume that you expose to the right, so those >> three stops are represented by the three MSBs. >> >> At ISO 100, your data will vary in range from 0x200 to 0xFFF. However, >> at ISO 12800 your data will vary from 0x001 to 0xFFF, so you will have >> all 12 bits of data to express those three stops of light. >> >> I might be making some critical mistakes involving noise floor, or just >> from not looking at the difference in the numbers of photons represented >> by a least significant bit. However, there is a good chance there there >> is someone on this list who is nerdy enough to have already worked out >> the math. >> >> > > -- > Science - Questions we may never find answers for. > Religion - Answers we must never question. > > > -- > PDML Pentax-Discuss Mail List > PDML@pdml.net > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and > follow the directions. -- -- Reduce your Government Footprint -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
