Lenses are brand based with ones like Sigma and Tamaron making them for all major makes of camera. The thing is though is the performance of a Nikon lens for example will have a Canon counter part. If you get that Canon though you will only be able to use EOS lenses and the compatible ones made by a outside company.are lenses made for specific camera's or for a wide gamma of camera's
not necessarily. i can get a better macro ratio out of my canon 24-70 or even 17-40 than i can out of the 70-200 f/4 L because of the macro ratio and the minimum focusing distance. this isn't very practical when what your trying to photograph has quick feet or wings and a mind of it's own when you invade it's personal space, but i couldn't imagine trying to shoot macro shots with the 70-200. each lens has a minimum focusing distance and a macro ratio that you need to be aware of when you're thinking about macros.if you use the telephoto end of the larger lense you should be able to get quite close in without being actually to close to the subject.