Beyond the obvious optical quality loss, the speed is too slow to use in AF mode. You need to have a 5.6 lens or faster to AF. When you put a 2X converter on a lens that is 5.6, you make it a F11 lens. AF won't function very well. You will be best served just picking up a longer lens than what you currently have.
Bruce Monday, September 30, 2002, 9:42:47 PM, you wrote: BR> My own personal opinion is to use teleconverters on prime lenses only. They BR> compromise the performance of the lens and, in the case of a zoom, the lens BR> is already compromised. BR> Bob Rapp BR> ----- Original Message ----- BR> From: "James Adams" <[EMAIL PROTECTED]> BR> To: <[EMAIL PROTECTED]> BR> Sent: Tuesday, October 01, 2002 1:44 PM BR> Subject: AF teleconvertor for Pentax SMC-F + Takumar-F >> What AF Tele-converter would >> you recommend for use with the >> Pentax SMC Pentax-F 1:3.5-4.5 >> 28-80mm and Takumar-F 1:4-5.6 >> 70-200mm Auto Focus lenses. >> >> I currently have a Vivitar MC >> 2X [PK-A/R-PK] Tele Converter >> and an Izumanon X 2X Auto Tele >> Converter [PK]. Neither of >> which work with AF lenses. >> James >> >>
