I got a 500cm and found it's harder to focus on the screen came with it (the one just has + in the middle. It is bright but i am near sight and with either contact lenses or glasses I am having trouble to focus -- i cannot tell if it is razor sharp on the screen. I have an old rolleiflex, which has a ground glass in it, i have no problem focusing on that screen, even without the magnifying glass. So I am wondering if there are any good focus screen that I can use on the hasselblad? Thanks.