I don't know about changing the screen but I use a old FL 55/1.2 lens in my A1 - the lens does not have an auto stop down mechanism so I have to shoot with the DOF lever locked in to make the lens stop down when I twist the Fstop ring. The camera will meter correctly on auto - the Fstop data does not appear in the finder, only the shutter speed. I focus with the lens open at 1.2 and then stop down to shoot. I don't care that the split image goes dark as I've already focused. You would need to find a non-split image finder to avoid the dark finder when stopped down. I honestly prefer the split image focus screens to any other screens that I've used in other cameras.