I expected someone to say that the PC-E is only 19mm while the Canon - released a few years ago already - is a more impressive FL of 17mm. 
The price, well... one could almost get a Canon TS-E and a Canon body to go with it.
(say, a used 5D Mark II; since it's a MF lens anyway the slow AF doesn't mean a thing).

The price, well... one could almost get a Canon TS-E and a Canon body to go with it.
