I have used the current Summicron M 50 for several years. Apart from a tendency to flare in backlit situations, with a strong light source just outside the scene, it is a stellar performer. I have not used the Summicron 40 myself, but judging from other peoples work it is also a very good lens. The last statement concern B&W photography; I have no idea how good the 40 is with colour film, but the 50mm’s colour rendition is quite neutral to my eyes.
I believe that you should focus on the difference in focal length instead. If you like 50 mm lenses, or if you already own a good 35 – buy a Summicron 50. If you like slightly wider lenses – by all means, buy a 40 in good condition.
Last edited by Uhner; 09-30-2007 at 04:32 AM. Click to view previous post history.