[davidmanze]

I have the Samyang 8mm  fisheye ( stereo projection lens)  on APSc it has no black circle, what a great lens for the money, you have to stop down a little though, but when you do it's very sharp, supersharp in the center and the colours are great, but it's real forté is it's resistance against flare.

  In the Pentax mount the aperture is controlled from the body, in the Canon I think it's all manual.

 Unless you need to shoot a lot wide open this lens produces crackling images and all for a bargain price!