Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
05-03-2009, 01:39 PM   #46
Senior Member

Join Date: Oct 2007
Photos: Gallery
Posts: 120
Original Poster
QuoteOriginally posted by F16 Quote
It just depends on the camera and lighting conditions, and when using a TC some will have a more negative impact on AF than others. Take a lens rated at 5.6 and try to AF in a dim interior room and chances are decent that AF will struggle. Take the same lens out on a sunny day and it will behave much differently. You can get a lens with the equivalent of F8 or even F11 to AF under ideal conditions. The rough conventional number is somewhere between F5.6 and F8, the reality is that there is no hard number, it will just depend on the circumstances.

Which camera body has advantage in the same circumstances?

05-03-2009, 03:27 PM   #47
Senior Member

Join Date: Feb 2009
Location: U.S.
Posts: 106
QuoteOriginally posted by Adnan EROL Quote
Which camera body has advantage in the same circumstances?
In the Pentax family of cameras, I couldn't answer that - I don't know what camera you're using and I don't know, for example, if low light AF performance is worse on a K100D vs. a KM/K1000 or K20D. My comment was more of a general comment that some AF SLRs perform much better under low lighting conditions than others. But I'm not that familiar with head to head low light AF performance between the Pentax DSLRs. The new KM is supposed to have the fastest AF performance overall, but that doesn't mean it's the best performer in low light.
05-03-2009, 03:35 PM   #48
Loyal Site Supporter
Loyal Site Supporter
Canada_Rockies's Avatar

Join Date: Nov 2007
Location: Sparwood, BC, Canada
Photos: Gallery | Albums
Posts: 9,629
QuoteOriginally posted by Lowell Goudge Quote
... <snip> ...
one additional point I discovered with the AF TC, and it is only because I now have my first KA mount lens, is that the TC corrects for apature when mounted to the KA lens. An F1.4 lens shows as F2.8 in the viewfinder.
Yes, I have noticed this with my 50-135 when I tried it. This may end up as my only converter after a while. It's only 1/2 stop slower than the 1.4X - S, and seems to give a bit better quality with the 400.
05-15-2009, 11:22 AM   #49
Senior Member

Join Date: Dec 2007
Location: Denmark
Posts: 146
I just go myself an AFA 1.7, and I'm finding that while focus is spot on with one lens, it front focuses quite a bit with another.

I've got a K10D and have been looking forward to a K7 upgrade (skipped the K20D) with lens specific AF adjustment - but I don't suppose it will recognize that the AFA has different lenses mounted to it.

Any ideas if this can be solved, or if I'm stuck in a "just doesn't work with this particular lens" situation?




  • 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!
adapter, autofocus, k-mount, lens, pentax, pentax lens, slr lens, smc, type
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
Any way to hack lenses to manual focus in AutoFocus mode (like the kit lens)? skyredoubt Pentax DSLR Discussion 8 08-07-2010 10:36 AM
When buying new lenses, do you demand FF capability? emr Pentax SLR Lens Discussion 34 02-21-2009 02:41 PM
Autofocus for manual lenes *could* be possible, read and tell me what you think konraDarnok Pentax News and Rumors 7 03-21-2008 10:31 PM
For Sale - Sold: FS: Autofocus film cameras and autofocus lenses Not Registered Sold Items 15 03-17-2008 07:08 AM
autofocus vs manual (new to k10d) REDEYE Pentax DSLR Discussion 18 07-24-2007 02:10 PM

All times are GMT -7. The time now is 12:50 AM. | See also:, 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?
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]