Depends on the work a pro did, for a photojournalist a fast and reliable motor drive, fast lens and pro build, for a nature, wildlife, scientific or medical photographer it may be a interchangeable prism very long lens, and a bellows, and pro build, for others it was rent-ability, could he/she rent lens and even a body if needed. What all pro level cameras have in common is a pro build, SLR or Rangefinder. Although Miranda and Konica had great features I would not consider either to be a pro level system. Minolta and Pentax dabbled with pro level but never really produced a consistant line. Hit or miss, Nikon and Canon were spot on.
Originally Posted by blockend