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06-22-2015, 05:51 AM   #1
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Some strangeness with my K20D

I noticed that recently that once I turn my K20D on, it finds focus pretty easily, but after about a minute or two it starts to really, really struggle. I might focus on something, then focus to infinity and try to focus again on the same item, and then all of a sudden it hunts like crazy, often not being able to achieve focus again. I tried 2 or 4 lenses, same behavior.

Any ideas what could be causing it?

06-22-2015, 07:54 AM   #2
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Odd thing, last year my K20D started doing the same thing. I originally noticed it if I was shooting for an extended period of time with my Sigma 50-500. I thought it was the lens, but it would focus just fine on my K10D, and like you said it would focus with the K20 would be just fine when you first turn the camera on. I later noticed that it was also doing it with other lenses as well and that the time required before it would show symptoms after start up got shorter and shorter. I did find that if I focused on something close and then moved back to the distant subject it would often focus in on it, at least once anyway.

I have had the camera since new and it was serviced a couple of times over the years by CRIS. When this started happening Pentax was in the process of switching from CRIS to Precision and I was hearing horror stories at the time, and the camera is long out of warranty so any money spent on repair could easily go toward another camera, so this was the impetuous to get me to finally break down and purchase a new K3 instead and haven't really shot much with the K20 since then as it is only a back up camera now.

So I'm sorry, but I don't have an answer for you as I still don't know what is wrong with the camera. I assumed that it was some circuit overheating or something like that, due to the age of the camera and the amount of pictures that I have shot with it, but I'm not really sure.

Steve
06-22-2015, 08:03 AM   #3
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It is really curious. At least I have a Katz eye split screen in there, and for manual focus, it still works as good as ever.

But, I'm really wondering what happened to the AF!
06-22-2015, 10:19 AM   #4
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QuoteOriginally posted by Spodeworld Quote
It is really curious. At least I have a Katz eye split screen in there, and for manual focus, it still works as good as ever.

But, I'm really wondering what happened to the AF!
Perhaps a little dust on the AF sensor? It is in the bottom of the mirror box.


Steve

06-22-2015, 10:23 AM   #5
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QuoteOriginally posted by stevebrot Quote
Perhaps a little dust on the AF sensor? It is in the bottom of the mirror box.


Steve
So what you're saying is all that dust your built in dust remover removes from the sensor gets dumped on the AF sensor? Hmmm... interesting design philosophy there if true.

The last time I used my K20D I had major AF issues as well. I might need mohave it cleaned, or figure out how to do it myself.
06-22-2015, 10:27 AM   #6
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The one time something close to this happened, it was time to charge the battery.
06-22-2015, 10:34 AM   #7
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I hope that doesn't happen to mine.

I do have to say that the whole camera needs a +5 AF adjustment - something it didn't need a year ago (or maybe I just didn't see it back then...).
06-22-2015, 10:59 AM   #8
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How do you get in there to clean it?

QuoteOriginally posted by stevebrot Quote
Perhaps a little dust on the AF sensor? It is in the bottom of the mirror box.


Steve


06-22-2015, 12:17 PM   #9
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QuoteOriginally posted by Spodeworld Quote
How do you get in there to clean it?
I have never done it and have no particular information except that it is on the floor of the mirror box and faces back towards the sensor. Other users on this site have cleaned the face lens for their AF sensors, but I don't recall the details.


Steve
06-22-2015, 01:30 PM   #10
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I've just looked at the AF sensor on my K20 and part of the lens is visible. You could try a small sable artists brush (new) with the end bent back on itself. If you can achieve this without the end breaking off or shedding hairs, it would dislodge the dust. One of the air blowers, not the aerosol type, would get rid of most of the dust. A fully charged battery will be required and the camera set for sensor cleaning. First look at the lens using a dental mirror and a small torch, taking care not to touch the CMOS sensor.
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