why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
tomtom50
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Re: why not f/1.2 by Sony?
In reply to ilza, May 19, 2013

ilza wrote:

I’m afraid you need to get your knowledge of basic physics of photography up a little bit.  What I would agree with is that the whole subject of comparing different form-factors it too obfuscated; too many people talk about things they do not have any clue about.

It helps if one thinks in correct terms:

Yes. It is important to realize when matching a lens to a digital sensor that the optics do not end at the lens.

Unlike film digital sensors have their own optical systems, including lenses. The photons need to follow a path through the sensor, past wires (DSLR sensors are not BSI)  before they can be counted at the photodiode, and that path is sensitive to angle of incidence, more on some sensors that on others. Quantum efficiency is not a single number; it is dependent of the angle the light strikes the sensor/microlens system.

Dxomark rates T stops for tested lenses, and their transmission testing includes the sensor. That is why Dxomark reports different full-open T stops for the same lens.

Look up the Sony 36mm f1.4 and check the empirically obtained T stop for various cameras. You will find significant variation.

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