Does anybody work with the 6-elements 50mm f2.8 Omega enlarging lenses? I saw one at my local thrift store in great shape in its bubble (I inspected it), but I couldn't buy it now because the store owner hasn't set the price on it, and the clerk was only a temp. I'm looking to replace my cheapy Vivitar one, but I was wondering if it was worth the buy, even at a low price.