I just finished a comprison, shooting the same subject but this time stopped down to f/22, f/32 and f/45. As you will recall, my post about wide open and near wide open apertures left a lot to be desired as far as color correction was concerned. The stopped down slides exhibit no color fringing at all. A big difference! The cause? The lens has bad color correction in the marginal zones and excellent color correction in the central zones. This is known as spherochromatism and is closely related to longitudinal chromatic. All telephotos have this it's just a matter of degree. Steve

-- Steve Rasmussen (srasmuss@flash.net), April 19, 1999