Leaf -- NEX-5 & Carl Zeiss Jena Flektogon 35mm f2.8. Click to see larger.
The last time I used a Flektogon 35mm f2.8 was four years ago, and it was an M42 mount. Not really sure why I sold it. Must be running out of money for new toys. A while ago I picked up an Exaktar version of the same lens, complete with box, for a really low price. Just got my Exaktar to NEX adapter last Friday and finally got a chance to use the lens.
The Flektogon 35mm has two versions: an f2.8 and a newer f2.4. Both versions have one outstanding close focus capabilities to 0.18 meters! Another related neat feature is that as you focus closer and closer, the maximum aperture scale changes to indicate lost of light (but the actual aperture blades don't close down!) when near closes minimum focus distance. Neat!
I find the lens to be just OK for distant scenes. It's quite sharp but not outstanding. What I love most is the close up capabilities and the image rendering characteristics. Very pleasing bokeh with nice light transitions. The Flektogon f2.4 is optically better. If you are looking for a 35mm Flektogon, buy the f2.4 version if you could. The f2.4 version I once owned had lots of mechanical problems, so be sure to check out everything before buying.