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 largely doesn’t matter what shutter speed you set on the RZ body as long as it’s slower than what’s set on the lens – that way the shutter baffle in the body should be open long enough to allow for any exposure set on the lens. I never tried slow shutter speeds but I don’t see a problem.)
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…