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If you want across the frame sharpness, avoid the Voigtlander 35/1.4. It's more of a "vibe" lens. The ZM 35s are much better across the frame, but they do have slight color shift, if you're picky. The Contax G 35/2 is decent all around, but isn't sharp like its 45/2 brother, or either of the ZM 35s.
So the color shift would be an issue even at 35mm on the 6. Hmm. I have no experience with color shift other than on this forum, that is something that would bother me probably.
Thanks for all the suggestions folks, I appreciate it. I have some researching to do. I'll be looking at the NEX pictures thread more closely to see examples of the lenses mentioned here.
@ISO1600 - You are right. I really like the ergonomics of the kit with a native lens, and want to keep it small if possible. It was an exercise in frustration for me to put a big 'ol ZE grenade on the front of it, plus the adapter.
@Kit, douglas, [others] - I do have a little experience with the sigma, and at it's price, there is a very good chance I fall back to that while looking at others. I would like something faster than 4ish(?) (effective), but at the same time, I like that it is has a slightly wider FOV.