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12-26-2010, 10:56 AM   #1
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Join Date: Jun 2008
Location: Paris
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DA* 16-50: AF confirm issues at infinity

Hi all!

I have a DA* 16-50 which gives me a little concern in some situations: sometimes, if I focus on a subject close to infinity (so to speak), and then to infinity, I fail to get AF confirmation (red focus indicator blinking and beeping). If I then focus close, then again to infinity, no problem at all, it focuses correctly and I get the confirmation all right.
I do not have on the other hand any issue with such "micro-adjustments" at close focusing distances.
So it doesn't seem to be an infinity focus problem (it is capable of it).

This is the second copy of this lens that I've owned, and I seem to remember that the first copy also sometimes forced me to re-focus close and then again towards infinity. Luckily, it usually happened when I was shooting landscapes - which features (mountains, trees, etc...) have a natural tendency to stay put while I get on with that little adjustment . Thats probably why I didn't pay too much attention to it the first time.

I was wondering whether other DA* 16-50 owners had experienced the same problem. I am trying to figure out whether it is a "feature" of the lens, a minor weakness of a few copies, or something more serious.

Thanks in advance.


12-27-2010, 02:37 AM   #2
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Join Date: Jan 2009
Location: Budapest
Posts: 821
QuoteOriginally posted by nicolas1970i Quote
I was wondering whether other DA* 16-50 owners had experienced the same problem.
Just tested mine and it works fine. First focused on a building approx. 200 meters away then on a distant mountain and after a quick one step micro-adjustment I got focus confirmation. I've repeated it a few times and always got focus confirmation immediately.

Maybe you're trying to focus on something with not enough contrast for AF? What focal length did you use? Try focusing at 50mm and then zoom back to the desired FL.
12-27-2010, 02:56 AM   #3

Join Date: May 2007
Location: WW community of Pentax users
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Posts: 2,165
Yes, I had this problem.
The lens was - eventually - replaced, after long and multiple attempts at fixing it by Pentax.
In the process they screwed up the focussing on a lot of my other lenses. So, the lot had to be sent to Pentax as well. That wasn't the end but this would lead to far from your question.
Just to illustrate that the appearance of this problem was the beginning of a very bad experience with Pentax "service" for me.

Just a small remark though: focus confirmation is shown at the bottom of your viewfinder. It's a green hexagon. The red squares merely indicate which focus point is activated.

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