Richard K
This is an excellent if odd lens. You cannot beat it for distortion (thats its thing) so if you want normality, this is NOT the lens for you. I have a specific application (panoramas) to which this lens is well suited. It works well with my full frame 5d mkii as well as smaller sensor Canon cameras. Lots of fringing (what do you expect when at 180 degrees field of view? Very useful for my purposes but a specialty item for sure. What it lacks is a lock at 8mm (it has one set up for smaller frame cameras). At 8mm on a full frame sensor, you get a full circle. To achieve this, the lens shade MUST be removed. One REALLY ANNOYING thing is that the lens cap clip-on design does NOT work very well, its very easy for it to fall off exposing the front element to everything.