Fisheye lens adapters?

I have an older nikon D70s, which i love, and i'm just looking for a bit of a kick with fisheye lenses, i want a (high distortion) 0.25x lens adaptor on my AF NIKKOR 1:1.8D with a 52 mm thread, but the lens no longer focuses properly, wil this affect my images? Because i have been told it won't, i just need a second opinion.
cheers.

First off, you are aware that these are not real fisheye lenses, are you?

Furthermore, i wouldn't mount such an adapter on a telephoto lens, assuming that it is the 50mm/1.8D that you have in mind. If i ever used such a thing, i'd mount it on a standard zoom so i can zoom out for an even more extreme view. At 50mm you'd already get 12.5mm though… Perhaps one that is less extreme would be a better choice, and that one on a standard zoom then? 0.42x or so?

Well.of course misfocusing will affect your images - you'll have to focus manually then. If it's anything like a real ultra wide angle or fisheye lens, then the focus will be rather uncritical, due to the extremely deep depth of field of such lenses.

Easier to just do a fisheye effect in your editing program of choice.