The lens produced nice crisp images – from this point of view I was happy with it. It was also less expensive than a similar condition RZ lens.
One of the other benefits is that the mirror-up function is simpler than the RZ lenses – you just turn a knob on the barrel through 90 degrees and it’s ready to go.
The RB lenses are all-mechanical. Unlike RZ lenses, you set the shutter speed on the lens. (It doesn’t matter what shutter speed you set on the RZ body – the light baffle in the body opens and stays open, letting the light in regardless of the speed on the lens.)
Anyway, I was so pleased with the 90 that I went ahead and bought a 50, 65 and 250.
Then I ran into a problem: the 90mm jammed onto the RZ body. I tried for several minutes but nothing I could do would free it. Eventually, through some random combination of cycling the film wind-on lever and rotating the locking ring, I got the lens off. I was quite relieved, having had visions of having to send the whole lot off to a repairer.
I subsequently read that RB lenses frequently jam on and people have to take drastic measures to remove them. This put me off the whole idea of RB lenses so I have decided to sell all 4 and replace them with RZ glass.
So there you go. A cautionary tale. RB lenses will work on an RZ body but you’ll be taking your chances…