After getting the Sigma 300mm, I have gone and purchased a Minolta Maxxum 28-135mm f4-4.5 lens. I needed a mid - long focal length zoom (I tend to do most of my shooting between 50-200mm). I researched this lens very extensively and was impressed by the reviews. Many believe that this lens was co-designed by Leitz for Minolta. I think they are right. This is the sharpest zoom lenses I have ever had on an SLR (even wide open). Anyone with a Maxxum SLR or Sony DSLR should try to find one. This lens is worth the money (unlike the overpriced Maxxum 135mm f2.8).