This has been bugging me for a long time. I have had both RB and RZ setups, and have had 50mm lenses for both. The 50mm I had for the RZ was a later version with a floating element. It was really, reeeeeeeally sharp. On the other hand, I had three different 50mm lenses for the RB, and not one of them was sharp enough to really be usable. What I'm wondering is if there are actually nice, sharp examples of the 50mm for the RB. Did I get really unlucky or is it just a dog of a lens?