Originally posted by bmw However both of these are f:4.5 glass. WTF? Losing a stop and a third of light?
Welcome to the world of medium format where f/4.5 is not a slow lens. The reasons fall into two main categories, one having to do with lens design and the other with practical shooting:
1. Fast lenses (e.g. f/3.5 and faster) with large image circles tend to be a little on the huge size and I do mean huge.
2. DOF is a challenge as the frame size increases. Simply put, at commonly-used focal lengths and working distances f/2.8 is not very useful with the 645Z sensor.
Steve