Ivan,

All the 50mm RB lenses have a floating element and if this is not used it could explain some of the "whines" about lack of sharpness.

By Ivan Bruce on Monday, August 30, 2004 - 10:33 pm:

I'm scouting for a used 50mm lens. I've heard mixed reviews, some say it's tack sharp and others whine about it's softness.
Depending on when the lens was manufactured, is there a difference? Have ALL the 50's been made with the floating lens for critical focusing? I've seen a couple of 50's go pretty cheap on ebay, but I can't get an answer from the seller if it has a floating element. Please help me buy the right one.
Ivan