[wirrah]

You can also use Av with M42 lenses on the *ist D. This is how I always use them on my *ist D. It obviates the need to press the green button. I am assuming this works for later models.

Set the lens A/M switch to manual. Set the camera to Av. The camera will continuously set the shutter speed based on the aperture setting on the lens. You should do your focussing at maximum aperture first for a brighter image.

cheers

Greg