I saw a test many years ago of the bog standard 50mm F2 Summicron where the sharpness was shown as a graph. It was so impressive that I have never forgotten about it. I cannot remember the scale it used but the graph started off quite high on the scale. For purposes of argument say this was at 7. (At F2)Iit then rose to say 9.5 and stayed flat all the way across the scale covering all apertures until F16 when it dipped to 8. That to me is very very impressive. Keep the Summicron and sell the Zeiss.