Hi,


can't tell you which is the most appropriate lens for your purposes, but this might help your decision:



  • a rectilinear lens is not a fish-eye, it's a wide-angle lens that (attempts to) make straight lines appear straight, not with the "extreme barrel distortion" of a fish-eye;
  • every lens illuminates a circle within the camera; a diagonal fish-eye illuminates the whole camera sensor, while the circle illuminated by a circular fish-eye is so small that it doesn't, so you actually get a circular-shaped imaged on your rectangular sensor; of course you need to take the crop-factor into account, a circular fish-eye for full-frame will just leave the corners dark on your 40D.




I have been playing with the idea of a fish-eye too, and will probably get a Lensbaby Composer plus the optional fish-eye optics. That's not the highest quality glass, but for half the price of a Canon 15mm fish-eye you get two lenses with lots of possibilities to play ;-)


Ciao, Colin