Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
06-14-2010, 08:31 AM   #1
Forum Member




Join Date: Feb 2010
Location: Colorado
Posts: 56
DA 70mm F/2.4 Ltd.

Why would a Pentax DA 70mm f/2.4 Ltd. lens not autofocus with a Kenko Pz-AF 2X teleconverter while a DA 21mm f/3.2 lens will autofocus with the same TC?

06-14-2010, 08:34 AM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,958
It should work. Why wouldn't it? Both lenses use the same screwdrive-based AF system.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-14-2010, 09:03 AM   #3
Forum Member




Join Date: Feb 2010
Location: Colorado
Posts: 56
Original Poster
QuoteOriginally posted by Adam Quote
It should work. Why wouldn't it? Both lenses use the same screwdrive-based AF system.
In theory it should work. I based my purchase of the DA 70mm on my use of the TC with my DA 21mm. But for some reason the Kenko doesn't work with the DA 70mm in the same light and same camera body (K10D). I would have bought the FA 77mm if I had known the issue beforehand.
06-14-2010, 09:05 AM   #4
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,958
That's very strange. I don't see why you would ever want to use a TC with a 21mm lens (except for testing, of course), but I can see it coming in handy for the 21mm. Without the TC, does the AF work fine on your 21mm?


Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-14-2010, 09:30 AM   #5
Forum Member




Join Date: Feb 2010
Location: Colorado
Posts: 56
Original Poster
QuoteOriginally posted by Adam Quote
That's very strange. I don't see why you would ever want to use a TC with a 21mm lens (except for testing, of course), but I can see it coming in handy for the 21mm. Without the TC, does the AF work fine on your 21mm?
Both the 21mm and 70mm autofocus just fine without the TC. Plus I agree that the 21mm with TC are just useful for testing. But here's something even stranger. With the TC, the 21mm autofocuses on my K10D but not on my K7 body. And I just discovered (subsequent to my post) that the 70mm with TC autofocuses on my K7 body but not on the K10D. Go figure!

Last edited by fredok1; 06-14-2010 at 09:32 AM. Reason: add clarifying wording
06-14-2010, 09:31 AM   #6
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,958
Sounds like some sort of electronic inconsistency. Maybe others know more about it.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

06-14-2010, 11:31 AM   #7
Pentaxian
Marc Sabatella's Avatar

Join Date: Sep 2006
Location: Denver, CO
Photos: Gallery
Posts: 10,686
Maybe it's just insulted? It's extremely unlikely the IQ from this combo will be what you'd get simply cropping.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
autofocus, da, da 70mm f/2.4, f/2.4, k-mount, lens, pentax lens, slr lens
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax 17-70mm f/4 or Sigma 18-50mm f/2.8 or sigma 17-70mm f/2.8-4? shang Pentax SLR Lens Discussion 8 05-24-2010 05:30 AM
Sigma 24-70mm, Sigma 28-70mm, or Tamron 28-75mm? gkreth Pentax SLR Lens Discussion 7 05-23-2010 01:01 PM
For Sale - Sold: Pentax-A 35-70mm f3.5-4.5 zoom, Vivitar "28"-70mm f/3.5-4.7 zoom, both wth iss Nick Siebers Sold Items 7 10-06-2009 09:01 PM



All times are GMT -7. The time now is 06:42 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top