I'm looking for a fisheye or ultra wide lens for my camera, but are a bit unsure of what to get. I can't afford the $1000 sony fisheye, but I've found a variety of fisheye's that fit my camera here: New and used sony alpha fisheye, Cameras Photo on eBay.ca So my question is... are these any good? Or are they just cheap ones that won't work/won't take good pictures. Also, what do the .20, .25, .42 numbers mean? Thanks!