(02-14-2020, 02:22 PM)toni-a Wrote: Transmittance or T stop is very important mainly for lenses desiggned to be used in low light, you might pay plenty of extra $$$$ for a f1.2 lens over f1.4 lens for low light performance to discover that both are equal or worst the f1.4 lens has a lower T value and thus transmits more light
can the transmittance be measured her in our tests ??
DXO is doing it so it is feasible
No, DXO is NOT doing it. DXO claims they do, but that is nonsense.
Their published T-stop values are just nonsense, and do not take into account the extra amplification a camera applies because of the F-stop used. Do I need to give examples, or will you accept me just telling you it is nonsense?
It is NOT doable with most lenses using cameras, and even if the lens would allow what you have to do, you still have to have very specific knowledge about what the camera is up to to kinda measure T-stops.
How would you go about measuring T-stops? In the middle of the frame you get a lot more light than in borders, let alone corners. So... What and how to measure it? And how to defeat the camera's manipulation? And how to distract the light lost by the sensor microlenses?