elluDe wrote:
I've read suggestions that using ISO-160 (and higher multiples such as 320, 640 etc) may give better results than ISO-100, 400 etc. This was on a 40D and also a 1Dmk3. Although it seems surprising that the higher ISO might produce better quality images, the suggestion was that this was because 160 was the native ISO on these cameras.
Using 160 instead of 100 isn't going to make much difference to shutter speeds, but I'm wondering if anyone finds this makes a difference to picture quality?
If ISO 160 was base ISO, then ISO 100 would have been called ISO L. So the assumption that ISO 160 is base ISO is wrong. Also, if 160 is base, then ISO 125 would have to be pulled as well, resulting in even lower noise than 160. But that's not the case.
X and a third stop ISO is an exposure that has been pushed by a third. X and two third stop ISO is X+1 which has been pulled a third of a stop. ISO 160, 320, 640 and 1250 are all of the pulled variety which, at the cost of a little dent at the saturation side of the dynamic range, slightly reduce the amount of noise.