DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
bobn2 Forum Pro • Posts: 55,645
Re: ISO, noise, exposure, and total light

awaldram wrote:

bobn2 wrote:

awaldram wrote:

This gain increases the noise for any given exposure solution.

It really doesn't.

Acording to ISO 12232:2006 it does

Please explain where. So far as I know, ISO 12232:2006 says nothing about 'gain'. Nor does it say that 'gain' will increase 'noise'.

So you have a copy.?

I don't have a copy, I have access to a copy.

ISO 12232:2006 specifies the method for assigning and reporting ISO speed ratings, ISO speed latitude ratings, standard output sensitivity values, and recommended exposure index values, for digital still cameras. ISO 12232:2006 is applicable to both monochrome and colour digital still cameras.


Though it doesn't explicitly state gain increases the noise for any given exposure solution it does suggest methods for assigning and reporting ISO speed ratings, which implies Gain which intern implies noise.

So, the answer is, I'm right and you're wrong. The standard makes no mention of gain. The suggestion that 'assigning and reporting ISO speed ratings' implies gain is yours alone, and it is wrong. As also is the implication that 'gain' implies 'noise'. Gain, as an abstract concept, of course does not imply noise at all. Even as a practical concept, a decent amplifier would have a SNR of 80dB or more, while with typical base ISO exposures we are talking a shot noise SNR of about 40dB. So, the 'gain' related noise is 40dB or so below the shot noise, effectively irrelevant.

Sorry I make assumptions base on my knowledge that causes me to jump to conclusions omitting steps along the way.

That would be OK if your knowledge allowed you to jump to correct conclusions.

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