These adapters are normally used for Prosumer cams to widen their wide end, from say 36mm to 28mm thereabouts.
I have used a Raynox version and it is Made In Japan. The quality is great. But the price is not cheap. I got it at $199 2 years back.
For DSLRs, get a proper wide angle lens like 24mm, 28mm or 35mm
Thanks Felixcat, now i got the idea abt the lens converter after reading up abt it..