Hi, I have a Hasselblad 500C. To focus I use the regular viewfinder it came with the camera. I am assuming the focusing screen also came with the camera. (This camera I bought it second hand). I also bought from Kiev, the russian middle format maker, a 45º viewfinder. With this one, it is a bit harder to focus. It is not as if with the regular viewfinder may be a piece of cake to focus with, but it is much easier! I am blaming it all on the focusing screen! Is there a "cleaning" solution for the focusing screen that you may want to recommend or is there a brand name or model for a used screen that you may want to recommend?? Thank you, kind regards, igmolinav : ) !!!