Now, this is another fisheye lens, the Sigma 10mm. I have a crop camera (Canon 40D) so I have to decide if I wanna keep the Sigma 10mm or the Canon 15mm. Both are pretty comparable in sharpness, focusing is fast, colors are both great as well. The difference is that the Sigma has a wider angle, the fisheye effect is greater. With the Canon, the fisheye effect is more subtle, which at times can be more beneficial. I would want to keep the Sigma normally because of the wider angle, and if I sold the Canon, I could get more money for it. BUT the Sigma has a really crappy petal lens hood that can't be removed, and when used with the built-in flash, produces a dark square shadow on the bottom of the pictures. It's a result of the petal lens hood blocking the bottom half of light from the built-in flash. Meaning I would have to use an external flash each time flash is needed, or no flash at all. Other than that, I am LOVING this lens!

