Originally posted by little laker If I remember correctly the book recommends that we focus with the lens wide open, then close the ring to the desired f-stop anyways.
So we're just forced into doing that the book says to do.
The camera keeps the lens wide open until you press the green button (in which case it closes the iris to the set value) or when you press the shutter. It's really a simple thing to do. The green button (and the AEL button on K*00Ds) are very near the shutter, it's much, MUCH simpler than having to open the aperture to focus, then take the camera away from your face to reset the aperture ring to the desired value (or try to remember how many notches you turned it).
It would be better if Pentax had not crippled the mount, but hacking at the aperture lever is much more disabling, I would say.
Even after only three weeks with my K20D, I already find manual operation very easy. What's more, you don't even have to press the green button each time, only when your scene changes.
Try focusing with a lens stopped at f11 and see what you prefer