Originally posted by climbmountainway There are two Tamrons, one the F series, which can work with all PKAF lenses made. No other teleconverter works for all of these, with the exception of the DA APS-C format $500 1.4X converter. All other 1.4 or 1.5 converters do not have the in lens motor to camera body contacts.
Just a small correction to this passage in a very informative post.
I have the Kenko Pz-AF 1.5x Teleplus SHQ teleconverter in Pentax mount. It is reputed to be a twin of one of the Tamrons that you mention; in fact despite being designated 1.5x, the Kenko's real magnification is 1.4x. As the "Pz" indicates, the Kenko also has the so-called "power zoom" contacts, and will drive a lens with SDM, DC or PLM autofocus, as well as screw-driven AF lenses. The AF does work with the DA 18-135 (DC AF) or the 55-300 PLM, although (as has been pointed out) the narrow maximum aperture on each lens at its long end limits the effectiveness of either combination except in very good light (135mm f5.6 on the 18-135 becomes effectively 190mm f8; 300mm f6.3 on the PLM becomes effectively 420mm f9). I don't have any SDM lenses to try it with, but people who have tried the Kenko/Tamron with pz contacts with an SDM lens such as the DA*300 f4 seem to rate the AF performance somewhere between mediocre and unusable. Pity, because unlike the Pentax DA 1.4x TC (which has been shown to vignette severely with the DA*300 f4 on the K-1), the Kenko/Tamron twins are FF compatible.
Last edited by Des; 06-09-2018 at 07:05 PM.