So I'm looking to get a telephoto lens and there is one on ebay right now that I am currently watching and will most likely bid on. However the weird thing it says its a Sigma lens lists the rest of the info but doesn't say what mount...someone asked the seller what camera it would work on and he lists all 5 that sigma says it will work on (sigma,canon,nikon,minolta,pentax). So is it possible for this lens to fit all these cameras? Or is it possible that the seller doesn't know which, and if I get the lens and it's made for nikon is there a way to use it on a canon camera with an adaptor of some sort? Honestly I know squat about lenses so this is probably an easy answer type thing, but I don't want to be stuck with lenses that won't work on my camera. Thanks for the help!!!