Quote Originally Posted by Trivette
There seems to be such a kneejerk tendency to try to divert people away from Leica optics that I sometimes wonder whether there might be a tiny bit of non-objectivity involved. I happen to have a 50mm Summicron (latest version), and it is for all intents and purposes optically flawless. There certainly may be better lenses out there, but it would likely be a test bench superiority, not something which would be noticed in practical use.
For what it's worth, a few years back I was shooting a series on 35 mm which had a lot of backlit subjects in it. I started out with a Leica M3 with a new 50 mm Summicron, the flare of this lens in backlit situations drove me nuts, even with a correct Leica filter and the lens hood pulled out. Aside from that, this was a very sharp lens with excellent field flatness. I also tried a Nikon FM2n with a new 50 mm f1.8 AIS lens, bad flare again. I disposed of both of these cameras and went back to Pentax and a 43 mm f1.9 lens - excellent sharpness, admittedly not the high micro-contrast of the Summicron, but great flare suppression.

I also have a new f1.5 Nokton - in terms of flare, this seems to behave like a Leica Summitar (immediate forerunner to the 1st version of the Summicron), although I have to say the lens hood supplied with the Nokton is ridiculously small. I now have a bigger hood but have not tested the lens for flare yet with this hood.

Of the lenses mentioned so far, the Zeiss could be a good choice, although for less money an f2.5 Color-Skopar could be good. Being a wizened old photographer, I tend to select a 4-glass lens for better flare suppression - of all the lenses I own, the champ for flare suppression has to be a 360 mm f5.5 Tele-Xenar. Only 4 glasses and single coating, but it never flares even with the sun in the picture or more critically just outside the frame.