correct me if I am wrong, but it is the maximum aperture of the lens TC that matters on an automatic lens, not what you have stopped it down to, since the AF is done with the lens wide open just before the lens is stopped down and the shutter opens. So a setting of F22 on an F5.6 setup will make no difference to the AF capability compared with say F8. Putting a TC on a slow lens is a problem because even wide open, the light levels are already too low for accurate AF. I doubt whether Alan's F9-11 combination will allow AF because this is as open as the lens can go
Alastair On 24 March 2014 09:25, Paul Stenquist <[email protected]> wrote: > I've tried autofocus at up to f22 with the 1.5X and the DA8 60-250, and it > worked fine, although that was with a high contrast scene. > > On Mar 23, 2014, at 2:32 PM, Alan C <[email protected]> wrote: > >> Very nice. What was the range, Paul? You've inspired me to dig out my old >> Vivitar MC 2x teleconverter which I used to use with a Vivitar (A) 75-200 >> f4.5. I'll try that combination & also with the FA100-300 f4.5-5.6 on a >> distant subject with the K7 & see what happens. MF, of course. It will be >> interesting to see if the AF confirm still works at f9 - f11. >> >> Alan C >> >> -----Original Message----- From: Paul Stenquist >> Sent: Sunday, March 23, 2014 7:54 PM >> To: Pentax-Discuss Mail List >> Subject: PESO Flying Rat, European Version >> >> Shot on a lake this afternoon. K-3 DA* 60-250/4 with the 1.4X converter, >> f5.6, 1/2500, 350mm, ISO 400 >> >> http://photo.net/photodb/photo?photo_id=17716268&size=lg >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. >> >> --- >> This email is free from viruses and malware because avast! Antivirus >> protection is active. >> http://www.avast.com >> >> >> -- >> PDML Pentax-Discuss Mail List >> [email protected] >> http://pdml.net/mailman/listinfo/pdml_pdml.net >> to UNSUBSCRIBE from the PDML, please visit the link directly above and >> follow the directions. > > > -- > PDML Pentax-Discuss Mail List > [email protected] > http://pdml.net/mailman/listinfo/pdml_pdml.net > to UNSUBSCRIBE from the PDML, please visit the link directly above and follow > the directions. -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
