Toralf Lund wrote: > Digital Image Studio wrote: > >> On 24/08/07, Toralf Lund <[EMAIL PROTECTED]> wrote: >> >> >> >>> Isn't the ISO rating (of the sensor) directly linked to the >>> signal-to-noise ratio? [ ... ] >>> >>> >> > what I was trying to say, is that I think I've > read somewhere that the "real" ISO is related more to the > signal-to-noise than the saturation level, i.e. that it may be defined > as the amount of exposure needed to reach a certain signal-to-noise > ratio, or something. > Actually, Wikipedia says:
ISO Standard 12232:2006 <http://www.iso.org/iso/en/CatalogueDetailPage.CatalogueDetail?CSNUMBER=37777> ("Photography — Digital still cameras — Determination of exposure index, ISO speed ratings, standard output sensitivity, and recommended exposure index") defines ISO speed in terms of the amount of light needed to achieve a certain "quality" in the sense of a per-pixel signal-to-noise ratio. but also However, this standard ISO speed "rating" for a digital camera is not necessarily very related to the ISO "setting" or "exposure index" used on the camera. As I suggested earlier, I always thought that what was referred to the native ISO of the camera was the actual rating according to the ISO spec, and that selecting another ISO value in reality only meant that the signal from the sensor was amplified by (setting/native ISO), but perhaps it's not quite as simple as that... The actual ISO standard is not available for free, of course. - Toralf -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net