5D MKII ISO 4000 missing?

Started Apr 3, 2012 | Discussions thread
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Re: 5D MKII ISO 4000 missing?
In reply to AndreeMarkefors, Apr 4, 2012

Yes that's right in terms of the effects.

As I understand it, though, the push-pull story is not quite right.

Rather what is happening is that the analog signal amplifiers has one stop settings - to get the intermediate ones an auxiliary amplifier (which adds noise) is used.

The main amplifier settings are in one stops from 160 (maybe unamplified is 100; but you can use 160 with no increase of noise or loss of DR)

The auxiliary amplifier operating on the 160 gives you 200 and 250, then the main amps next setting is 320.

The reason this makes no real difference after about ISO 1600 is that at that point the photo site noise swamps amplifier noise, making these differences irrelevant.

It's also at this point that the dynamic range of the Canon sensors is up there with the Sony, because Canon's photo sites are as good, it's just their analog amplifiers and read noise that are slightly noisier

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