This may be the wrong forum but I cant find one for light measurements and guessed people here may use a Pentax spotmeter. Anyway I have just dug out my late fathers Pentax spotmeter. It's simple enough to use, just point and dial in the ev number to the dials on the meter to get a reading after setting the film speed. The slightly confusing part is that the ev display does not change with the film speed i.e. the wall here measures 7 ev regardless of film speed set. If I then set 7ev on a Hasselblad lens the resulting combination of shutter speed/aperture could be way out because the meter reads the same at all film speeds and the lens has no way of knowing what film speed is being used. I am fairly sure the meter is working correctly so should I assume the meter ev readings are always for a set film speed and if so does anyone know what it is? or am I way off the mark? Many thanks, Jim.