I have been shooting Canon for about 40 years. About three years ago I finally got into digital with the 7D. Less than a year ago I bought the 5D3. Great cameras! I have a nice variety of primes and zooms (all Canon) and it is always nice to have something super-wide. I bought the Rokinon 8mm for the 7D and was very happy with that lens! Since I am shooting moistly FF now, I decided to sell the 8mm and buy a mint Canon 15mm on eBay. It is the highest S/N that I saw and is quite mint. I have to say that I am just a bit disappointed with the lens. The Roki had a really nice snap and contrast to it that I am not seeing in the Canon. I used the Roki on the 7D and the Canon 15mm on the 5D3 doing very similar shots, at night games, in our SF Giants ballpark. I believe the coverage is about the same. I sold the Roki to make room in my wallet for the Canon. Seriously, the photos are fine until you go pixel peeping. There is a lot of CA and they just do not have the contrast, color rendition or feel of the Roki. Is anyone out there using the Canon fisheye? Do you feel that it is sharp? I think I shot mostly at f5.6 since it was night and at pretty high ISO's (never an issue with Canon, IMHO). The physical size and all is really perfect. It works out to about a 24mm when on the 7D body, which is nice. In the wide range I have the 24-70 f4 and the 28mm f1.8 prime. I am just curious to hear from other users about their thoughts about the quality of this lens. Is it worth sending in to Canon to have it evaluated? Nothing seems to be wrong with it, but it simply does not seem to live up to the quality standards that I expect from Canon. Thanks so much!