Hi, are all SLR camera lenses a uniform size/shape etc? Will any lense fit into any SLR camera or do you have to follow specific lenses for specific cameras?
I'm not sure I agree with Novalis. The lens made by Canon for example for their EOS and supplied with the standard product are not great. OK so there are a variety of more expensive lens Canon also make for it.
However the mid-priced range of lens produced by folks like Tamron and Sigma are broadly reckoned to be much better than the basic lens.
This applies to other makes of camera as well.
As already mentioned, Tamron and Sigma make compatible lenses. I bought a zoom Sigma lens for my Canon and was very pleased with it. Still pleased 5 years later...