Christiaan Phleger - Honolulu , Jun 11, 2006; 11:43 a.m.
I believe the 3 screw vs 5 screw may make a difference long term slightly for the relatively heavy optic, although my 50mm 1.2 Ai has only 3 screws and seems to support the weight OK. I do prefer the Ai series for the longer thread pitch especially with such a fast lens with a narrow angle of depth of field. However, I think most of the differences may be on the order of purely argumentive, since this is such a rare and worthy optic, they all are great. I tested one for sale 10+ years ago and am still kicking my self for not getting it at the measly sum of 750.00!