why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
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Re: why not f/1.2 by Sony?
In reply to tomtom50, May 19, 2013
Have you read F stop blues at Dxomark?


Very worthwhile when considering the usefulness of fast lenses on a digital camera.

It is interesting, but their choice of using T-word where F-word is due is abysmal.  When T-number is mentioned, one assumes that the light loss is discussed (as opposed to the angle of incoming cone of light hitting a point on a sensor). T-number affects the exposure, F-number affects also the diffraction and the circle of confusion due to misfocus.

While what they measure (I assume it is the photon noise) may be, technically speaking, the T-number, the observed difference between the cameras cannot be attributed to difference in light transmission in the lens.  My immediate conjecture is that what they observe is due to vignetting in the microlenses; then this would affect the diffraction circle and the circle of confusion in a similar way to a mechanical limiter of the aperture ring.

(Well, the difference with mechanical limiter is that the bokeh must be significantly improved with such vignetting… :-))

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