I have been using a Hasselblad 501CM for a few years with the waist level viewfinder, an have come to the conclusion that I need a prism viewfinder for my landscape work. I looked at Keh.com and it looks like there are many choices available. I'm looking for some insight to help me make a choice. Is a 90 degree prism more suitable for landscape work than a 45 degree prism? Since I have physical limitations, I would like to keep the weight down. I assume that the non-metered prisms weigh less than metered prisms.