As an answer to another question I posted a few weeks ago, a member indicated to me that the Mamiya RB67 210K/L lens was an outstanding piece of glass. I already have a 180mm "C" lens, and I was wondering how much better the APO optics are compared to what I have. Would it be worth it for me to buy a used 210 KL for around $400.00? I'd love to hear the opinions of anyone here with experience using these lenses.