I bought an M42 to FD adapter w/ the idea of using my Helios lens on my Canon T90. After looking at the manual, I am not very clear on how to do the metering. The manual refers to using FL lenses by using the lens in stop down mode and pressing in the stop down switch on the camera. Obviously that wouldn't work w/ the Helios lens. I was hoping to simply set the aperture and let the camera set a shutter speed. Will that work, or am I going to have to manually meter it? I set the camera to AV and set the ISO to agree w/ my handheld meter. When I stop the lens down it agrees, and when I'm in different lighting the shutter speed goes up and down accordingly. So, is that it? Anything else I'm missing?