Can someone please help me with diopter eyepiece choice for the EOS 3? I recently picked up a Canon EOS 3 for a film photography course at my local college. Before that, I was shooting digital with a Canon Rebel XTI. On the Canon Rebel XTI, I was able to get fairly clear vision through the eyepiece with the diopter adjustment set to the maximum - position --could be slightly better with slightly more - diopter. I read that this is -3.0 diopter on the Canon Rebel XTI. I would like to get similar results from the Canon EOS 3 eyepiece but I read that the Canon EOS 3 has built in -0.5 diopter. Can someone please tell me how the -3.0 diopter ED eyepiece would calculate with the built in -0.5 diopter of the Canon EOS 3? Would the Canon ED -3.0 eyepiece be a -2.5 eyepiece, which when added to the built in -0.5 diopter makes a total of -3.0 diopter, or would it be a true -3.0 diopter eyepiece, which when added to the built in -0.5 diopter makes a total -3.5 diopter?