I never could focus on ground glass, although I also like microprisms more than split image, although I got the split for my RB67. At the moment we are trying to get a prism or microprism screen for my wife's old EOS 650, which seems to be having a new lease of life. The original (German) instructions say that there was quite a range available, but they aren't available anymore. The auto focus is a bit hit and miss, and we both prefer manual anyway, as we know what we want to focus on. Does anyone know if Canon's current screens fit it? We wrote to Canon, who say they don't know!