Adam, I own the Summicron & not the Planar, so I can only say that the Summicron is a superb lens. User reports seem to be universally very, very positive about the Planar. The only tests that I know of are by Erwin Puts (
www.imx.nl/), who says that the Planar is optically at least the equal of the Summicron.
Other than optical performance, what other considerations might be part of your decision? There is Leica's reputation for superb build quality & the ease with which you can obtain parts & repairs on Leica equipment - even if Leica went out of business tomorrow. OTOH, price is a consideration. On the grey market (
www.popflash.com or
www.cameraquest.com), the Planar can be found for less than half the price of a new Summicron. I should note that I paid the same price ($600) for my Summicron used on ebay as the grey market price for Planars, but since Planars have now been on the market for 9 months, they have also started to pop up on the used market. A used Summicron from a dealer is more expensive than on ebay or on this forum & others like it.
What about the CV Nokton? I'll leave user reports to others, but there are some distinct differences. It is a larger lens (54.5 mm) than the other 2 (43.5 mm) which are almost identical in size. Its minimum focus distance (35 inches) is not as close as the other two (27 inches). It is faster, although Popular Photography found it to be not quite as fast as advertised (f/1.6 maximum aperture) & the Summicron to be slightly faster (f/1.9). Its measured focal length is also longer than advertised (53 mm). There would seem to be enough differences here to help make a decision.
My decision would be:
1. Summicron for professional use, for those to whom money is no object, & for those who are comfortable buying used. Build quality & repairs are both factors here.
2. Planar for typical enthusiast who wants to buy new, or for professionals on a budget, or for those who can't learn the Leica handshake. Quality control on these lenses is excellent even if build quality may not prove to be up to Leica standards over the long term. The latter is probably not an issue unless the lens is subjected to the rigors of professional use or the like.
3. Nokton as a budget alternative, or for those who really need the extra half stop, or for those who just prefer the ergonomics of a bigger lens.
My 2 cents . . .
Huck
