Hello there, I have an old Pentax 67 in my hands, with a SMC Pentax 67 165mm f/2.8 lens on it. The lens has a AUTO / MANUAL switcher. Since it's a fully manual camera I guess I need to keep it in "manual", nevertheless I read somewhere that it needs to be in Automatic for the meter to work? I'm confused. Extra info: - The meter needle moves in both settings - The viewfinder becomes darker/lighter while changing the aperture only in the manual mode.