I want to get a m/f lens suitable for portraiture. I have a Mamiya 7II, but would the 150mm lens be too short for portraits (70mm in 35mm terms)? Would I be better off getting something like a s/h Hasselblad 501 and a 150mm lens? Or just stick with my Mamiya c330 and 135mm lens and keep chopping the top of people's heads off when I forget about the parallax?