I bought a Canon fd 50mm f1.2 lens for use with my GH2. I notice when I turn the f-stop adjustment ring on the lens barrel that there are about four more clicks left when the iris opens to it maximum amount. That is, the aperture leafs reach a point and then the ring will turn approximately four more clicks with no further aperture change. Is that normal? How can I tell when the aperture is fully open?

I have that problem with my adapter ring, too. It doesn't click, though, it's smooth, it just has more travel past the fully open spot.

I wonder how to determine if the aperture is actually fully open.

I wonder how to determine if the aperture is actually fully open.

Can't you just look into your lens from the front? I have a Nikkor 55mm 1.2 and when its wide open.. I can't see the aperture blades at all.

That's what I'm thinking, John. Jim get a flashlight and look in if you need to. The issue is no doubt adapter related, IMO.

I have a friend with the same lens. I will do a comparison and report what I observe.

I reseated the lens into the adapter and it works fine now.

Jim, this is why, when I used legacy lenses, I had an adapter for each lens. Changing adapters was a real nightmare on the job, wasn't even feasible, as it was so tricky for me to get it right quickly.

I'm so glad to be done with those lenses. On the other hand, because of them, I learned more than I ever wanted to know about exposure and shutter speed, which I needed to learn anyway, so that was a good thing, in the end.