Recently I purchased a fisheye adapter for my Canon T2i for around $12 off of Amazon. It seems to work (I’ll do a review later), but I wondered if there was someone out there that had made one. Well thanks to a quick DDG search, I see that someone has tried this, with a donor pair of eyeglasses.
Apparently to achieve this effect, you need to use “positive” lenses meant for people that are farsighted. From there, it’s just a matter of taping the lens onto your original DSLR lens.
You’ll reportedly have to use the manual focus when the lens is on, otherwise things will get a little screwy with your focusing mechanism. Also, if you try this kludge, be sure to zoom your original lens out as much as possible to allow things to work together well.
As for how effective in widening your camera’s field of view this DIY fisheye lens is, you can check out a bunch of photos taken with it here. It’s really pretty hard for me to tell how well it works, but if you have a set of glasses ready for the trash, this experiment might be worth a try. Otherwise, I’d probably stick with the $12 purchased solution.