Possible fish eye using Opteka video lens?

So, the Opteka Fish Eye 37mm 0.3x (http://opteka.com/opts​c37fe.aspx) is made for video cameras with a filter size of 37mm. Now, I was thinking... hey, if you get a 37 to 55 step up adapter, would this work on a dslr?

first off, those are optically not very good. Second, you'd be using a step-down ring to get a 37mm filter on a 55mm lens, meaning you'll have huge vignetting with a little round picture in the center.

That's what I was thinking. Thanks!

No prob. You'd be better off looking for a used canon fisheye, or if you can't swing that, the Rokinon/Samyang offerings are manual-focus-only but really nice.