DOF and Cropping take 2

Started Feb 11, 2014 | Discussions thread
awaldram Forum Pro • Posts: 13,126
Re: I shall spell it out for you.

To my understanding

iso-less is just a coined phrase with no true meaning but is used to signify when a cameras read noise (after already being amplified to 'base ISO') is so low that whether you use in camera ADC gain or external digital gain in PP you get no appreciable difference.

I don't think any camera has been proved to be really ISOless all it means to me is the the reduction in SNR is equal for analogue gain or digital gain and doesn't not indicate that the reduction in SNR does not occur at all.

So ISOless does not mean without ISO but rather you can apply that ISO after capture with little or no penalty over doing at capture time.

That gain is still required to achieve a correct exposure and the more you do the more noise and less DR you have remaining.

I don't really see at applicable to the point I'm making ... Sensors have normalized gain such that iso100 produces the same exposure across sensor sizes.

Surely that’s a given.?

If that is true (which I'm sure it is ) and small sensor receive less light (density) than large sensors then it stands to reason to reach that same standardized ISO scale the small sensor most have more gain applied.

It makes no odd whether your talking iso 80 or iso 256,000 to reach that standard scale the small sensor has more gain applied and as per Chicago Universities dissertation this adds significant noise as compared to read noise.

I don't think were miles away from consensus we both agree in general noise is a factor of sensor area not pixel density just disagreeing on what causes that effect.

One other thing probably worth adding is fill factor but then again that probably makes no odds within a technology point.

The other things that spring to mind that are szie realated and so tend to only apply to subsets is heat (larger sensor more heat higher noise) BSI doesn't scale.

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