Finally got around comparing my two favorite wide angle primes,
the Voigtlander Skopar 20mm/3.5 SL-II pancake and the Zeiss Distagon 21mm/2.8 ZE, both in Canon mount, I use them on the Canon T2i, 7D and 5D2 and via adapter on my Panasonic Gh1. The Zeiss Distagon has the edge when it comes to image quality but the extremely small size and low weight of the Voigtlander make it my favorite walk around lens. And lets face it, the quality is still extremely high and better then most wide angle zooms (one notable exception is the Nikon 14-24mm), extremely high center resolution wide open and it sharpens up nicely once stopped down to 5.6 (on full frame, the edges are not a problem on a cropped sensor). Manual focus is a piece of cake on ultra wide angle lenses and very enjoyable on both, the Zeiss and the Voigtlander. I keep the Zeiss around for crucial work but 9 out of 10 times I grab the Voigtlander because of its tiny form factor.
Here are the links to the Voigtlander MTF and Zeiss MTF charts at photozone.
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