AC016
Senior Member
I watched a video the other day and the fellow was talking about T-Stops. It is used more in the cinematography world though. However, when you compare it to F-Stops, you will get a better understanding on the light transmission within lenses. The more elements you have in a lens, the more light you need, just like the big honking telephotos. With all those elements, light is lost at each element it hits. This is where T Stop comes in. It measure the effective transmission of light through a lens. So, you may have a F2.0 lens, but how effectively does that lense transmit light to the image plane? If you have a big telephoto lens with a F Stop of 5.6, your T Stop is probably going to be closer to F8 or F10. Good prime lenses with less elements will have a T Stop value closer to the actual F Stop. Again, T Stop is all about how effectively a lens transmits light to the image plane. F Stop is only the relationship between the lenses optical diameter and the focal length. Anyhow, there is more to it than this and other variables do come into play. Though, this is just a very basic explanation to introduce perhaps some new terminology.