I've been considering getting a ring flash as I'm keen on macro and tired of the shadows I get with my 430ex. I've had a look and canon do the ring flash and the twin light flash and sigma do a ring flash. Does anyone have any experience in differences in quality between them? The sigma ring flash is a fair bit cheaper than the canon one. I have the 60mm canon macro and 150mm sigma marco lenses so naturally the flash would have to be compatible. I know the sigma is but not sure about the canon. Any info on that?