Sensor sizes and f stops

Started Jan 25, 2014 | Discussions thread
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Re: Light reaching each pixel
In reply to olliess, Jan 26, 2014

However, more pixels, and hence more photons, will be used to form any given area of the final image. The upshot being, the SNR normalized for the print area/resolution should still be better for the larger sensor.

This is a common presumption people make, however noise does not average as nicely as people think it does.

As SNR gets lower averaging becomes much harder, to the point it's actually useless.

We can see this when we consider how effective reduced image sizes are at handling high ISO noise in some camera. Mush in, mush out, to put it crudely.

There is another side effect. SNR also limits DR. Small pixels lead to lower DR. You cannot average that out. So even if I accepted the idea that averaging worked well enough, the reduced DR is a killer.

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