Compact, high performance rear tele converter which is specially optimised for Pentax lenses. Extends the focal length of the lens by a factor of 1.4 times. Weather resistant, dust proof construction for all weather shooting. Compatible with both in lens AF (SDM / DC) and in body AF. Autofocus is retained when used with a Pentax lens with a maximum aperture of f/4 or brighter. HD coating designed to minimise reflectance inside the lens while optimising light transmission.