Originally Posted by dreilly
Ah, the EV interlock. I've used cameras with these before. It's a great system IF you have a light meter that reads out in EV. Many of the old ones do, and I think even the newer digital ones do as well, or can be set to. Once you know the EV number and set it on the lens, the shutter speeds/apertures are locked together so you can do the archaic equivalent of the "program shift"--change the f-stop/shutter speeds while maintaining the same exposure. 1/60 at f8, 1/30 at f/11, etc.
Oh, I like both of those shots above. Great textures on the bottom ones!
The EV interlock can easily be disconnected by a good service person, I use a IIIA with it disconnected, doing so also frees up the rings which makes the camera very fast and easy to use. I'd recommend having it done it to anyone using them.