IVSB is a very nice Leica III copy and it feels like a block of iron in your hands. It's small but surprisingly heavy. I had one that I used mainly with a 21mm lens with an auxiliary viewfinder. I soon found out that bottom feed cameras are not my thing. The Canon P feels and operates like a real RF camera. I never had any problems with the viewfinder. 35mm frames are far in the corners but you soon get used to that. While I had a Canon P I also bought a Leica M4-P but after a year and a half I sold the Leica and kept the Canon(s).