a7S high ISO claim - - -over hyped or not ?

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LSHorwitz1
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a7S high ISO claim - - -over hyped or not ?
5 months ago

As a long time satisfied NEX-7 owner contemplating the possible purchase of an a7S, I am trying to clarify just how much of an improvement in low light performance I might expect.

Using DxOMark measurements as a starting point, I see that my NEX-7 is rated at 1016 and that the a7S is measured at 3702.

One might conclude that this measured less than a 4-fold increase in ISO should result in less than a 2 stop benefit, since each stop is a doubling / halving.

The comparison of the published specifications of two camera bodies as described by Sony however suggests a much larger gain, since one camera, the NEX-7, was specified as having a max sensitivity of 16,000 ISO, while the new a7S is described as having a max sensitivity of 102,400, over a six-fold improvement.

Is this claim by Sony over-stated, and thus the promised 6+ fold ISO gain increase claimed only really measureses to less than a 4 fold increase?

I would be disappointed to go from my current NEX-7 and all my associated glass to the a7S at considerable expsnse, only to find that the DxO measured improvement of less than 2 stops was all that I gained.

To avoid the confusion which may arise from Sony's offering extended ISO beyond 102,400 to 409,000, I want to ask anyone who replies to please leave this extended claim out of the discussion. I do realize that further claims by Sony to extend the a7S to yet higher extended ISO of 409,000 makes the a7S appear to have yet additional sensitivity, but I would judge this to be no more than manually "push processing" the sensor further, no different from manually setting my NEX-7 to expose a couple more stops underexposed. I am trying to compare both bodies based entirely on their measured sensitivities for their normal claimed range of ISO.

Thanks for any insights here,

Larry

Sony Alpha 7S Sony Alpha NEX-7
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