why not f/1.2 by Sony?

Started May 14, 2013 | Discussions thread
forpetessake Veteran Member • Posts: 4,892
Re: why not f/1.2 by Sony?

tomtom50 wrote:

stan_pustylnik wrote:

Do you know what a T-stop is?

Do you understand that the issues with digital sensors at very large apertures is actually compounded on top of the T-stop correction of the f-stop?

Here is a Dxomark article documenting that digital sensors do not fully use all the light from very fast lenses:


It is a real phenomenon. Light coming in at greater angles doesn't make it to the photodiode. Wide apertures cause the light to come in at greater angles.

Dxomark measures the T-stop of the system including the sensor.

The Sony 35mm f1.4 has T1.6 on the a900 and T2.1 on the a380. There is really no reason to buy a really fast lens if you have aan a380, the light is falling on the sensor but less is making it to the photodiodes.

Since we are talking about f1.2 lenses:

The Canon 50mm f1.2 is T1.7 on a Canon EOS 450D.

The Canon 50mm f1.4 is T1.8 on a Canon EOS 450D.

The f1.2 gives very little on that camera.

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.

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