There was a Ricoh f2 50mm lens from long ago which seems to have a reputation for great sharpness, and I'm just wondering whether it's the one I've got (which came on a Ricoh KR10 I bought on eBay a year or two ago). I recently bought a Pentax K10D with the intention of taking advantage of some of my better old K mount lenses and I'm in the process of rationalisation. The Ricoh I have says 'XR Rikenon 1:2 50mm S' on the front. Is this one I should keep? There is a minor problem with it in that the depth of field scale has rubbed off but I can live with that. Optically it seems OK but I'm not expert enough to be able to know how it compares with others.