I'm going to swap out the original Focotar 40mm on my Leitz Focomat V35 for a Schneider APO lens. I'm not concerned with preserving the autofocus really. What I do want is the best possible optical performance from my new lens. So should I go for the APO 50mm or the 40mm? I've read several posts talking about how the the APO Schneider is superior to the Focotar, but what about Schneider 40 vs 50?