[kpaddie]

Difference lenses have very different MTF (resolution vs how far away to the center of the lens) in theory and because of the different lens internal structure, they also have different fringing, distortion performances as well. The bokeh look different depending on the shape and the number of aperture blades. Sometimes it is not clear whether spending 2x or more is worth it so this is I believe very helpful to help buyers to see what's the actual differences of lenses are without all those fancy ads.