Originally posted by eyeball Also, although admittedly not designed for this purpose (like an actual preset ring on say, the 28mm shift lens), you can sort of use the AUTO/MAN switch as a preset: choose your aperture with the ring, then switch to AUTO to focus, and then to MAN to stop down to meter with the green button.
If you use Av mode, you don't have to use the green button to meter. The camera should meter automatically. I'm referring specifically to M42 lenses here. The aperture stops down as soon as you move the slider to MAN.