Quote Originally Posted by StoneNYC View Post
T stop? I've never seen that and I have some cameras from the 1910's how old is that "system"?


~Stone

Mamiya: 7 II, RZ67 Pro II / Canon: 1V, AE-1, 5DmkII / Kodak: No 1 Pocket Autographic, No 1A Pocket Autographic | Sent w/ iPhone using Tapatalk
T-stops are used primarily for motion picture lenses - they provide a more exact measurement of the light transmission of a lens then the slightly more theoretical f-stops.

The difference is usually small, and generally only relevant in the exacting circumstances of motion picture work.