mi è piaciuta molto questa parte:
"Some people suggest that some manual focus lenses are better then their Canon AF equivalents. For example the manual focus Zeiss 21mm f2.8 is sais to be significantly better than the Canon 20/2.8 or any of the wideangle zooms which cover 21mm, and is, in fact, one of the very best wideangles available, especially in terms of corner and edge sharpness. I can't confirm this myself since I haven't personally used one, but I see no reason why it couldn't be true and it certainly appears to be the case judging from image samples I've seen posted on the web. However, it will cost you around $1700 new (the Canon EF20/2.8 is closer to $400), so it's certainly not a cheap or convenient route to optical quality!"