When I shot with Mamiya TLR cameras, I used 55mm, 80mm, and 180mm lenses for a variety of subjects. When I shot portraits, I used the 55mm for group portraits. I used the 80mm for full length, 3/4 length, and half-length individual portraits. I used the 180mm for head & shoulder portraits, head shots, and face shots.
The 135mm may have also been a good portrait lens, but at the time, I was unable to economically justify it.[/QUOTE
The 180 is difficult to use indoors especially in small rooms the 135 is all in all IMO the most generally useful portrait lens.