Forgot Password
Pentax Camera Forums Home

Show Printable Version Search this Thread
08-05-2011, 03:24 PM   #1
Inactive Account

Join Date: Jan 2011
Location: Kent, UK
Posts: 6
Landscape Autofocus Problems...

I recently took a trip to Italy, and used both a 50-200mm and 18-55mm - and both had trouble autofocusing at a distance when fully zoomed - I had to start reeling the lens in until it would focus...

I would say the conditions where hot (high twenty's to mid thirties) and humid on days, and with a white haze at a far distance.

In addition to the lenses, I was using only a ciruclar polarising filter - no UV filter.

Is this a problem with the conditions or the camera - could it have been fixed by using a filter?

Any help or experience would be appreciated.

Many thanks.

08-05-2011, 03:58 PM   #2
Senior Member
tackyat.2's Avatar

Join Date: Sep 2010
Location: New York
Photos: Gallery
Posts: 181
It's possible that because the aperture of both your lenses at the longest focal length and your polarizing filter that the camera couldn't autofocus properly.

In that case, even trying to focus on something close wouldn't work.
08-05-2011, 04:05 PM   #3
Veteran Member
RioRico's Avatar

Join Date: Jun 2008
Location: Limbo, California
Posts: 11,264
Autofocus and focus-confirmation depend on the focus point(s) having some contrast or pattern. For instance, trying to autofocus on a blank wall or sky is difficult. Infinity may also be hard to autofocus. I would not use AF to shoot distant mountains etc -- I would manually focus to infinity (or just before) and set the aperture for enough DOF. But daytime shots of distant features with a long lens may be affected by atmospheric turbulence and particulates, which reduce contrast and clarity. Trying to AF on distant mountains at 200mm in daytime is an exercise in frustration.
08-06-2011, 12:26 AM   #4
Inactive Account

Join Date: Jan 2011
Location: Kent, UK
Posts: 6
Original Poster
Thanks for the replies - I opened this thread as I've never experienced this problem before.

It seems odd, (thinking back...) even if I took the CP filter off, it would still not focus properly... even moving the focus point around from a building to a tree to something else... trying to hunt a more contrasting focal point. The only thing that would help was to bring the zoom back in.

...this was using my K-r. I've had no problems taking distance landscape shots in the UK (Lake district, Dales, etc...) before, but perhaps I have and never thought it an issue! Saying that - those locations are pretty contrasting in the summer months.

My wife on the otherhand had no problems using only a 18-55mm with her K100D...

Just can't believe I've never experienced it! - I've just tried focusing at a distance on white sky (can't always focus) and distant roof tops (can't always focus, but better than focusing on sky!)...

08-08-2011, 12:11 PM   #5
Senior Member
Swapnil's Avatar

Join Date: Apr 2011
Location: Bellevue
Photos: Gallery | Albums
Posts: 147
As riorico has mentioned, K-r's AF works on Contrast detection. White wall, Clear Sky, Landscape with 50% and more sky has AF hunting. Its usually the case if AF points are selected to Auto, 5 or 11 points. There are two workarounds that I use

1) Switch to landscape mode, it drastically reduces AF hunting
2) Manual AF to infinity

Also, you can set the AF point to some high contrast point in the view, that will ensure that you are not focusing some low contrast area.
08-10-2011, 01:02 AM   #6
Senior Member
Elva's Avatar

Join Date: Sep 2009
Location: Grahamstown in the Eastern Cape province of South Africa
Photos: Gallery
Posts: 125
Was this on multi segment? Did you try spot focus. I have had the same problem in aviation photography and switched to spot and that worked fine. Skydiving photos with along lens at 500mm and blue sky is a real challenge to get both exposure and focus spot on, I normally use spot for both and bracket a little.

  • 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!
camera, conditions, distance, filter, k-r, kr, pentax k-r
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Similar Threads
Thread Thread Starter Forum Replies Last Post
P52-3-46 - Landscape - Portrait Landscape jmschrei Weekly Photo Challenges 11 06-13-2011 12:32 AM
Help! Autofocus switch stuck on AF.S and will not autofocus! pauldiebel Pentax DSLR Discussion 3 09-19-2009 08:59 PM
Autofocus problems with DA*16/50 and K100D Super jotarou1 Troubleshooting and Beginner Help 12 09-02-2009 09:48 PM
K10D Autofocus problems Joel Pentax DSLR Discussion 5 05-03-2008 07:06 AM
For Sale - Sold: FS: Autofocus film cameras and autofocus lenses Not Registered Sold Items 15 03-17-2008 07:08 AM

All times are GMT -7. The time now is 01:32 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]