the best possible optical results, teleconverters should be avoided as a
general rule but if one is needed, the Hexanon AR Teleconverter is probably
the best of all teleconverters available for use with Hexanon lenses. It’s a
superior 6-element teleconverter that received UC-grade lens
coatings. Even more importantly, it is a flat-field teleconverter, and this explains the much better image quality it produces as compared to the commonly available third-party teleconverters, especially if a quality lens is used. The Hexanon AR
teleconverter is well-regarded and sought-after.