(08-18-2021, 06:46 PM)toni-a Wrote: A concrete example: you might choose Sony Zeizz planat 50mmf1.4 over Sony Zeiss Sonar 55mmf1.8 because you gain one f stop in low light condition, however in fact both are tf1.8, they have almost same low light performance, f1.4 version has a shallower DOF
You should NOT look at DXOmark "test" data. DXO's T-stop values are total and utter nonsense. They can't measure T-stops, and what they publish in T-stop values is laughable.....
Quick example to illustrate their nonsense:
Sigma 35mm f1.4 Art. T-stop "Sony": 1.4. That is impossible. T-stop "Nikon": 1.6. T-stop "Canon": 1.6. SAME optics.
You can't (easily?) measure T-stops with camera sensors.
And one stop from f1.4 is f2, by the way ;-)