So I'm looking for a decent lens for the range of 70-300mm. I'm just beginning to do photography, so I'm not looking to spend the 400-500 on one just yet, so I've narrowed it down to three lenses. 1. Canon EF 75-300mm f4-5.6 III USM 2. Sigma 70-300mm f4-5.6 APO DG 3. Tamron AF 70-300mm f/4-5.6 Di All of them have the same aperture levels, and they're all about the same price, but is there anything that one of them have that makes it better than the other two? Any advice or comparisons between these three lenses? And if anyone uses any of them, picture examples would be great Any help would be appreciated!