Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-25-2021, 04:48 PM - 1 Like   #16
Loyal Site Supporter
Loyal Site Supporter
clackers's Avatar

Join Date: Jul 2013
Location: Melbourne
Photos: Albums
Posts: 15,322
When you narrow the aperture down, it gets to be difficult to get light from both ends of a line to converge on separated AF rows of pixels.

f5.6 is the traditionally accepted limit - after this, there are no guarantees.

In sports and wildlife shooting, you can see the lens and TCs acknowledge this ... you'd conventionally only use a 1.4xTC with an f4 lens, but could put a 2x on an f2.8.

In those disciplines, high performance AF is desired, compromises can hurt you!

11-28-2021, 02:13 AM   #17
Junior Member




Join Date: Feb 2021
Location: Havant
Posts: 25
A further test outside, 100% cloud cover,
K1 ii, FA 80-320mm, Kenko MC7 2x converter,
Shutter speeds varied from 1/13 at ISO 100 f5.6, to 1/100 at F10 ISO1600
AE works at 320mm F5.6 & F10. Single point (centre) af
on brickwork & some distant trees. There was a little hunting
on the trees, but I have had worse while tracking birds, in
good light against a clear sky, without a converter fitted.
11-28-2021, 07:08 AM - 2 Likes   #18
Site Supporter
Site Supporter
ramseybuckeye's Avatar

Join Date: Apr 2009
Location: Hampstead, NC
Photos: Gallery
Posts: 15,014
I use the DA 1.4 with the 55-300PLM at the beach or on water, places wher you also get a lot of reflected light. It works fine there, but itís not going to find focus in a wooded setting, I include a couple examples here, I included the second to show it was able to focus on the shaded side of the willet, but most likely because of the light reflected off of the sand, I doubt it would have been possible had the willet been walking on grass.



11-29-2021, 08:06 PM   #19
Site Supporter
Site Supporter
cdd29's Avatar

Join Date: Sep 2016
Location: Southern Indiana
Photos: Gallery
Posts: 466
Awhile back I thought I do something stupid (mainly because I was bored) and see how many teleconverters I could stack and still get some kind of image. Well, I was up to three and the camera had no idea what f/stop it was on (said f/1.7 which is impossible as it's an f/4.5. AF didn't work but I could get a workable image in daylight. That was with 2 2x and a 1.4 I believe. I have since acquired another 2x I might try and see if I can make the camera go into a fetal position...

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, camera, camera autofocus, f/5.6, f/5.6 lens, lens, pentax help, photography, troubleshooting
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
645 Teleconverter Conversion with Autofocus? TDvN57 Pentax Medium Format 4 05-04-2021 07:14 AM
K70 will only autofocus and shoot in monitor mode, not through viewfinder snobrewer Troubleshooting and Beginner Help 8 02-06-2021 03:06 AM
For Sale - Sold: Nikon F-801 AF film camera w/ TC 16A teleconverter-autofocus with manual lenses 17dew Sold Items 4 05-08-2016 08:10 AM
For Sale - Sold: quantaray 2X Autofocus teleconverter; Pentax 18-55mm kit lens idler Sold Items 9 07-02-2009 12:06 PM
In-Body autofocus vs In-Lens autofocus Gooshin Pentax DSLR Discussion 7 02-05-2008 11:10 AM



All times are GMT -7. The time now is 08:54 PM. | See also: NikonForums.com, CanonForums.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