Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-06-2016, 08:55 AM   #1
New Member
Grognard's Avatar

Join Date: Jun 2016
Posts: 23
Strange AF Issue with DA* 300

Well, the issue has been fixed, though. I just wonder why.

A couple of days ago, DA* 300 suddenly couldn't AF in OVF (the camera is K-1). No matter if I half-press the shutter button or press the AF button. Unlike the slowish hunting, the lens did not move at all! The lens was just bought a couple of weeks ago, so I didn't immediately call Pentax customer service but did some searches in the forum. With the search key word [DA* 300 AF issue] I only found one or two threads which are quite different from my case, so I was starting to concern about lens damage especially SDM malfunctioning.

Yesterday the lens still couldn't AF in OVF. But when it came to my mind that someone in the forum said "when you can't AF in OVF try it in LV", I immediately tried that and it really worked! To my surprise when I turned off LV and the lens could AF in OVF again. it seemed that AF in LV has ACTIVATED the SDM! I would no longer worry about physical damage, to my great joy. So I started to figure out the reason. After digging in my memory I remembered that the issue occurred after I changed the "Link AF point to AE point" option to ON. I changed that option back to OFF but in vain. Then I tried to change every system option related to AF (including the AF button) but no miracle happened. Every time when I leave the camera off for a while and restart it, AF wouldn't work in OVF; and AF in LV mode seems to be the workaround (activating the SDM).

Today I tried to AF in OVF with DFA 24-70 and the lens behaved snappy. After some analysis I came to the conclusion that both my K-1 and DA* 300 have no physical problems, and that the issues must be caused by camera body configuration. Then, as my last resort, I reset the camera settings. Finally it worked!

Issue solved. But I really wonder why. From all of my knowledge in K-1, system options allow users to enable/disable shutter button AF, or completely disable AF; but there's no option like "disable phase detection AF and enable contrast AF". What do you guys think?

08-06-2016, 10:18 AM   #2
Site Supporter




Join Date: Nov 2009
Location: Michigan
Photos: Gallery
Posts: 266
Interesting

Well you may have helped me with my similar problem. For a year or two now my DA* 300 AF has not worked immediately when I switched to this lens. I mount the lens, turn on the camera and attempt to focus through the viewfinder and the AF does not activate. I cleaned the contacts to make sure that was not the cause. My solution thus far was to turn the camera off and remount the lens. This always worked, both on my K-3 and now my K-1. I just did a test where I switched to Live View when the AF was non-functional and that activated the AF. When I switched back to the viewfinder the AF continued to work. For some reason this problem seems to only occur when I have not used the lens for a while. If I go back and forth between lenses in a short period of time the AF works. Incidentally I always use back button focus. Switching to Live View to activate AF is much more convenient than my old fix. I may eventually try restoring the camera to factory settings to see if that solves the problem in a more definitive way, but I'd have to make note of any customization I've done first.
08-06-2016, 10:40 AM   #3
Forum Member
gerardbaron's Avatar

Join Date: Apr 2011
Location: Mississauga
Posts: 61
QuoteOriginally posted by dave2k Quote
Well you may have helped me with my similar problem. For a year or two now my DA* 300 AF has not worked immediately when I switched to this lens. I mount the lens, turn on the camera and attempt to focus through the viewfinder and the AF does not activate. I cleaned the contacts to make sure that was not the cause. My solution thus far was to turn the camera off and remount the lens. This always worked, both on my K-3 and now my K-1. I just did a test where I switched to Live View when the AF was non-functional and that activated the AF. When I switched back to the viewfinder the AF continued to work. For some reason this problem seems to only occur when I have not used the lens for a while. If I go back and forth between lenses in a short period of time the AF works. Incidentally I always use back button focus. Switching to Live View to activate AF is much more convenient than my old fix. I may eventually try restoring the camera to factory settings to see if that solves the problem in a more definitive way, but I'd have to make note of any customization I've done first.
Same problem with a 28-105mm on K 1

Last edited by gerardbaron; 08-06-2016 at 02:14 PM.
08-06-2016, 01:07 PM   #4
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,866
QuoteOriginally posted by Grognard Quote
there's no option like "disable phase detection AF and enable contrast AF". What do you guys think?
PDAF is only available when using the optical viewfinder. CDAF is only available from live view.


Steve

08-06-2016, 03:23 PM   #5
New Member
Grognard's Avatar

Join Date: Jun 2016
Posts: 23
Original Poster
QuoteOriginally posted by dave2k Quote
Well you may have helped me with my similar problem. For a year or two now my DA* 300 AF has not worked immediately when I switched to this lens. I mount the lens, turn on the camera and attempt to focus through the viewfinder and the AF does not activate. I cleaned the contacts to make sure that was not the cause. My solution thus far was to turn the camera off and remount the lens. This always worked, both on my K-3 and now my K-1. I just did a test where I switched to Live View when the AF was non-functional and that activated the AF. When I switched back to the viewfinder the AF continued to work. For some reason this problem seems to only occur when I have not used the lens for a while. If I go back and forth between lenses in a short period of time the AF works. Incidentally I always use back button focus. Switching to Live View to activate AF is much more convenient than my old fix. I may eventually try restoring the camera to factory settings to see if that solves the problem in a more definitive way, but I'd have to make note of any customization I've done first.
So happy to have inspired you!

---------- Post added 08-06-16 at 03:31 PM ----------

QuoteOriginally posted by stevebrot Quote
PDAF is only available when using the optical viewfinder. CDAF is only available from live view.


Steve
Thanks for the reply! Yep you are right. But my problem was, why the PDAF unavailability can be fixed by switching to CDAF temporarily, or by remounting the lens (as reported by dave2k) or by restoring to factory default?
08-06-2016, 03:48 PM   #6
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 26,866
QuoteOriginally posted by Grognard Quote
But my problem was, why the PDAF unavailability can be fixed by switching to CDAF temporarily, or by remounting the lens (as reported by dave2k) or by restoring to factory default?
I suspect there is an internal problem in the lens internal focus mechanism that may resolve if the system is coerced to "home" the lens to a known state.

BTW...Welcome to the Pentax Forums!


Steve
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!
af, button, camera, cdaf, da*, da*300 k-1, dslr, factory, focus, full frame, full-frame, k-1, k1, lens, option, pentax k-1, sdm, view, viewfinder
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
DA 300* with HD Pentax-DA AF Rear Converter 1.4x AW SashasMom Pentax SLR Lens Discussion 17 12-06-2015 01:08 AM
For Sale - Sold: DA* 50-135, DA 55-300, AF-540 FGZ, AF-360 FGZ II Flash apisto Sold Items 16 11-24-2014 07:14 AM
DA*300 with Pentax 1.7 AF Adapter RockvilleBob Pentax SLR Lens Discussion 5 08-24-2013 08:56 PM
AF Teleconverter that will work with DA 55-300 ChopperCharles Pentax SLR Lens Discussion 9 06-05-2013 06:42 AM
K-01 AF speed with DA* 300 David07 Pentax K-01 6 12-04-2012 10:58 AM



All times are GMT -7. The time now is 09:39 AM. | 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