Alastair, I've used the 1.7AF a bit, but not in lower light. The AF hunting trick is new to me. I'll give it a try! Thanks. (And yes, they are going for outrageous prices.) Regards, Bob S.
On Dec 7, 2007 11:37 PM, Alastair Robertson <[EMAIL PROTECTED]> wrote: > Bob > > sorry wrote that in a hurry. The beauty of the F1.7x AF teleconverter > is that it can autofocus manual focus lenses (or AF lenses set to MF > as in my case with the Sigma 300). You manually set the approximate > focal length on the lens and put the camera on AF and when you fire > the shutter the AF mechanism drives internal elements within the t/c > to autofocus the image within the tolerance limits of the t/c (it > can't focus when the lens is set to a focal length that is a long way > from the correct setting for the subject in view). The result is a > very fast autofocus and no hunting up and down the focal length of the > lens, which is what tends to happen in low light levels when you have > a AF lens mounted directly. Some AF lenses have focal limits which > acheives the same sort of effect but is less flexible and slower than > the result using the t/c. Hope that makes more sense! > > see Boz's page if your not familiar with this beast > http://www.bdimitrov.de/kmp/teleconverters/F1.7X.html > > These things are like hen's teeth and fetch ridiculous prices on ebay > of more than $600! I am still kicking myself when I was too slow to > pick another one up from a NZ shop that had it at NZ$95 recently > (about US$60). > > Alastair > > > > > On Dec 8, 2007 6:16 PM, Bob Sullivan <[EMAIL PROTECTED]> wrote: > > Technically you just lost me... Regards, Bob S. > > > > > > On Dec 7, 2007 9:24 PM, Alastair Robertson <[EMAIL PROTECTED]> wrote: > > > http://www.pbase.com/image/90022721 > > > > > > Taken at home - trying to get bird pictures again, but captured the > > > white blooms of the rose "iceberg" up against the dark hedge. > > > > > > Specs: K10D AF1.7x Sigma 300/4 APO monopod > > > 1/2000 F4.0 ISO200 > > > > > > Not the sharpest combination at this aperture but quick AF response > > > since you set the approx focal length on the lens and put it on MF and > > > the camera on AF and even at low light levels the AF doesn't hunt > > > since you have effectively limited the focal length the AF of the > > > camera can explore. > > > > > > Alastair > > > > > > -- > > > 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. > -- 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.
