Could I use a TC and get AF with the Sigma 70-200mm F2.8 EX DG OS HSM?
Fair enough, at least I know. Thanks Strumstrum.
Bob
My website (Hadfield Photography)
Pentax Gallery Artist page:link
Flickr Photostream: link
http://www.sigmaphoto.com/article/notice-to-customers-using-sigma-tele-converter...
AFAIK, this is only true for Sigma's own TCs- but that TCs from Kenko and so on WILL autofocus with the Sigma HSM zooms.
BTW, in my experience (and of others, I understand) 1.4x TCs work OK, but don't expect the 2.0x TC's to be very quick to autofocus with these lenses.
John
K-3 II, K-3 and a K-70 from SRS

Bob
My website (Hadfield Photography)
Pentax Gallery Artist page:link
Flickr Photostream: link
These tend to be a bit rare and highly prized as Pentax only made powerzoom lenses for a relatively brief time in the 90s.
Here's a mini-review someone has put up:
http://www.clubsnap.com/forums/showthread.php?p=6475663
You can see the electrical contacts required on the left hand side of this picture:
http://i53.tinypic.com/2it0j8l.jpg
they're the 2 golden pins sticking up, inside the main metal ring.
Nope, only those with the 'pz' designation and the powerzoom electrical contacts (which the HSM focusing uses)
These tend to be a bit rare and highly prized as Pentax only made powerzoom lenses for a relatively brief time in the 90s.
Here's a mini-review someone has put up:
http://www.clubsnap.com/forums/showthread.php?p=6475663
You can see the electrical contacts required on the left hand side of this picture:
http://i53.tinypic.com/2it0j8l.jpg
they're the 2 golden pins sticking up, inside the main metal ring.
I stand corrected because my Kenko 1.4x IS a "pz" version and I thought most of them are that too. BTW, I never knew what the "pz" designation meant until now, and how it came to be - thanks!
However, it should be noted that most of us with the 55-300 Pentax have found that this is one lens that the Kenko does not work with very well. OTOH, the Kenko does seem to work at least moderately well with the 18-135mm Pentax and the autofocus does work with that combination - so it's still a handy thing to take on holiday.
Also since I have older, non-HSM 700-200 F2.8 and 100-300 F4 Sigmas and the Sigma 1.4x TC, I have not tried the Kenko with those (or not to a very great extent anyway)
K-3 II, K-3 and a K-70 from SRS

well with the Sigma 150-500mm, which is the only Sigma lens
I have. It also works brilliantly with the Pentax 55-300mm.
I also have the rare Tamron 1.4x which doesn't give very good images
with the Pentax 55-300mm but works with the DA*300mm f/4 and probably
the Sigma 150-500mm.
See this thread.
-
Half Man... Half Pentax ... Half Cucumber
Pentax K-1 + K-5 and some other stuff
Algi
Bob
My website (Hadfield Photography)
Pentax Gallery Artist page:link
Flickr Photostream: link
Snootchies
Member
Chester
Thought I'd ask and see if anyone knows more here.
Bob
My website (Hadfield Photography)
Pentax Gallery Artist page:link
Flickr Photostream: link