On Sun, Apr 10, 2011 at 05:27:53PM -0700, Larry Colen wrote: > In my typical geeky fashion, I'm trying to wrap my head around all of the > ramifications of adjusting sensitivity (ISO) on my camera. Please correct the > errors in my understanding. > > In the simplest form, it is a measure of how many LSBs per photon (or tens, > thousands or millions of photons).
[calculations elided] > Is this basically accurate? You're missing a few significant points. The ISO gain is an analog amplification stage, and so will itself introduce noise. The higher the gain, the more noise. The whole thing is an exercise in signal-to-noise ratio. Counting photons doesn't give you a whole extra bit of information if you increase the resolution of the counter, because you're summing inherently noisy signals. That means the signal- to-noise ratio only goes up about half as fast as you would expect; to get a factor of N increase in signal-to-noise ratio you need to increase the total count ny a factor of N squared. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
