I was wondering if someone would be able to answer my question. I have heard from reading that some lenses perform better then others of the same focal length at different distances from the subject. Some times people say a lens is optimized for portrait or macro and that it looses sharpness or micro-contrast when focusing on more distant subjects. An example is that I read a review that said the 40-150 pro is not as good as the 50-200 at the same focal length for distant subjects. I'm not sure how this would work or if it is even true. If someone knew the answer and why it would be helpful I making lens decisions.