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12-24-2010, 09:15 AM - 3 Likes   #1
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DA* SDM lens overexposure on a K5 - The moral is "don't panic."

To relieve any apprehension, let me say at once that this problem appears to have been resolved by cleaning the electrical contacts around the lens mount on my K5 (i.e. the K5 was not faulty as I feared initially). This will not be another "here's a new problem with the K5" thread. It is worth mentioning, however, as it appears that DA* SDM lenses are more susceptible. Other forum members may experience this, and potentially not just with a K5.

I have put over 5000 frames through my K5, and aside from what appears to be over-sensitive auto white balance (in comparison with my K7), it has been flawless. It has been the best camera I have used since 1977, and I remain stunned by its versatility and reach. Today I noticed that whenever I shot rapid frame rates at high ISO (25,600), 10 to 15% of the frames would be overexposed by about a stop or more. When I carried out some tests I found that the problem became less noticeable at lower ISOs, but much worse at 51,200. Firmware on the K5 was 1.01.

The problem was consistent whenever I used DA* SDM lenses (in this case a 50-135 2.8 and 200 2.8). When I tested the lenses on my K7, they were OK (no exposure errors).

I tested the K5 using two clutch-driven lenses (DA 40mm Limited and an FA 77mm Limited). There were no exposure errors at high frame rates. As the DA* SDM lenses have more contacts than the Limiteds, I got out a box of Q-tips and swabbed the contacts of my K5 (which I have to admit were dirty) and cleaned the contacts on both DA* SDM lenses. Once this had been done I repeated the rapid-fire test and the K5 was OK.

Worth keeping in mind before anyone having a similar problem returns a camera body to their dealer.

12-24-2010, 11:10 AM - 1 Like   #2
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Thanks for the heads up.
12-24-2010, 02:08 PM   #3
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Yeah, it's good to remember that a lot of apparent problems can be fixed with a little rational thought and a small amount of maintenance.
I'm terrible for remembering to clean lens mounts, I'm surprises it causes me as few problems as it does.
I wonder if my living in a very dry climate helps.
Thanks for the reminder and very good information, Delgado.
12-24-2010, 02:31 PM   #4
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Good report of a handy problem-solving exercise.
Thanks for sharing.

12-24-2010, 02:36 PM   #5
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I have a lot more exposure problems with Canon than I have with the K-5. There is no perfect camera - but many Pentaxian friend tend to think the K-5 needs to be. It is only the best, not perfect yet.
12-26-2010, 01:04 AM   #6
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Maybe the new dc motor done jobs better than those SDM ?
12-26-2010, 04:55 PM - 1 Like   #7
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Great tip. I think all my lenses and bodies are due for a good contact cleaning...
12-26-2010, 05:19 PM   #8
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QuoteOriginally posted by TZH Quote
Maybe the new dc motor done jobs better than those SDM ?
The problem was not related to the motor. It was an erratic over-exposure problem at high frame rates caused by dirty contacts between the camera body and lens - something I will be paying more attention to from now on. The irony is that I pay a lot of attention to keeping the glass clean, but have tended to take it for granted that the contacts stay clean. Close examination and swabbing with some dry Q-tips proved they also need attention.


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