I believe that the meter is simply reading the light as determined by whatever stop you're turning the uncoupled lens down to. When the match needle is on the correct spot (that bump at the top), you've determined the exposure and take the shot. I'm a hand-held meter guy, especially in a situation with an uncoupled lens/body combo so I can barely recall my actual use of this but do remember it working when I was playing with it. I recently tested a Nikon 55 Macro using the Nikon adapter but the body was an FT-1 (just checking macro performance vs my Hexanon). I was using studio lights and flash meter though. The exposures were right on, as one would expect by virtue of my flash meter. After the comparison, I sold the Nikon and don't have anything here to play with that I can adapt.... My old TC & T4 bodies don't have working meters anymore, either.