Was thinking about getting one of these for shadowless photography, especially with the up and coming release of the sigma 140DG(hopefully it'll be less than $400). Got a doubt here.
How do ring flashes attach onto a lens? I was reading up on the canon version and it seems it only fits onto certain lenses Does this mean that I can't use it with say, a third party lens? Must there be a special "mount" on the lens in order to use such flashes?