why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
EinsteinsGhost
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Re: why not f/1.2 by Sony?
In reply to forpetessake, May 17, 2013

forpetessake wrote:

tomtom50 wrote:

forpetessake wrote:

You need to keep in mind that we are not talking about really fast apertures here. The f/1.2 on APS-C format is equivalent to just f/1.8 on FF -- hardly a superfast lens. Testing with focal reducers also seem to indicate there isn't a problem going up to f/1.0 on APS-C.

Can you cite a source? I had the opposite impression.

I'm not sure what you are asking about and what your impression is. It's a trivial math, equivalent lenses are scaled by the crop factor. The 50/1.8 lens on FF has the same properties as 34/1.2 lens on APS-C, provided all other things being equal. Focal reducers are a living demonstration of that.

Focus reducers are also concentrating light onto a smaller area, which should (theoretically at least) result in faster shutter speeds than would be achieved on FF.

The f-stop, however, is not an accurate representative of exposure (light transmission), and more so at larger apertures. Unfortunately, manufacturers get away with simply quoting f-stops. I wish t-stop would be included, as they do for cine lenses.

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