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06-13-2011, 06:30 PM   #1
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Odd focus behaviour on DA16-45

I have a DA16-45 and I notice that sometimes it fails for focus accurately at a distance of over 10m. The problem seems worse in low light but does actually occur in full daylight. The important point is that the lens is not hunting and failing to lock onto a focus point, but instead it's locking onto a focus point that is wrong.

I've been reading about lens calibration but this isn't a case of the lens always locking out of focus, so I don't think calibration will help. Does anyone have any suggestions, and is there a documented process for lens calibration anywhere?

06-13-2011, 06:44 PM   #2
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I too have a 16-45 that has not been focusing accurately - its off, but very random - if that makes any sense. Its just on this one lens, so its not the body at all or any of the other lenses. I had it evaluated and the focus gears need replacing. Now, that is my problem, its not indicative of what your problem may be. I can say that my unit had NOT been extensively used, certainly not miss treated or dropped - but the gears do wear out. Repair cost will run $200 and change. Rather than have CRIS do it, I am going to send it to Eric.

Also, in reading here, I have not really run across any similar problems - so I just won the unlucky lottery.

06-13-2011, 07:04 PM   #3
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QuoteOriginally posted by interested_observer Quote
I too have a 16-45 that has not been focusing accurately - its off, but very random - if that makes any sense. Its just on this one lens, so its not the body at all or any of the other lenses. I had it evaluated and the focus gears need replacing. Now, that is my problem, its not indicative of what your problem may be. I can say that my unit had NOT been extensively used, certainly not miss treated or dropped - but the gears do wear out. Repair cost will run $200 and change. Rather than have CRIS do it, I am going to send it to Eric.
Your issue sounds very similar to mine if it focusses sometimes, but not at other times - randomly. I've used the lens a lot but I'd really be surprised if the focussing gears needed replacement after only a couple of years. I can't be sure, but I think this problem existed from new, but seems to have got worse over time.

Dumb question - who is Eric?
06-13-2011, 08:02 PM   #4
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QuoteOriginally posted by RobG Quote
Your issue sounds very similar to mine if it focusses sometimes, but not at other times - randomly. I've used the lens a lot but I'd really be surprised if the focussing gears needed replacement after only a couple of years. I can't be sure, but I think this problem existed from new, but seems to have got worse over time.

Dumb question - who is Eric?
Actually, I think that it has gotten worse over time, and I had questions when I first received it - new, 4 years ago. It was my first lens after the kits, and I believe that I did not evaluate it correctly. At times - a lot of the time, it was perfect, while other times it was off. Over time it has just gotten worse. In 20/20 hind sight, I should have sent it back for another copy - but that is spilled milk - my fault. It is what it currently is.

Eric is Eric Hendrickson who services and repairs Pentax cameras here in the states. He has done it since the Spotmatic days and is now retired, with a little shop at his house. Film camera and lenses he repairs, and brings back to life.....I hear/have read down in Oz the local distributor does a good job...



06-13-2011, 08:07 PM   #5
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I don't think this is normal. Get it serviced.
06-14-2011, 08:23 PM   #6
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Thanks for the feedback with respect to the 16-45; it sounds like I need to get it serviced.

Does anyone know of a guide to calibrating the AF on Pentax lenses, preferably with the K7? Faulty DA 16-45 aside, I'd like to get the best out of the lenses I have, and I have several others.
06-14-2011, 08:37 PM   #7
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I have used my 16-45 for quite some time and just noticed this yesterday and today. It never misses focus, it just won't lock focus occasionally on the wider end with the subject at a farther distance in broad daylight. It's never done this before and the green hexagon flashes at infinity focus even though the subject is in focus.
06-14-2011, 11:55 PM   #8
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QuoteOriginally posted by builttospill Quote
I have used my 16-45 for quite some time and just noticed this yesterday and today. It never misses focus, it just won't lock focus occasionally on the wider end with the subject at a farther distance in broad daylight. It's never done this before and the green hexagon flashes at infinity focus even though the subject is in focus.
I also find this especially in low light. The answer may be to try moving the focus point slightly so the camera is able to get a focus lock. I end up doing this quite a lot. I always have the camera set to centre point focus, so I often have to re-frame after the camera gets a focus lock anyway.

When I tried the interval timer I had to turn off the AF because otherwise the camera would change focus somewhere during the sequence - even though the subject was a landscape scene at infinity. So this demonstrates how the camera is detecting an erroneous change in focus given that the subject at the centre point was at infinity and the camera was on a tripod.

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