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07-18-2018, 02:49 PM   #1
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Pentax K-5 Auto focus not working on Prime/Constant aperture lenses

I tried the Pentax SMC DA Lens K - 50mm - F/1.8 and Sigma 70-200 F/2.8 on my Pentax K-5 Body. The camera Auto Focus doesn't work. I can shoot in Manual mode though. I tried the DA 18-135mm WR Lens on the Pentax K5 and the Autofocus works. Any thoughts?

07-18-2018, 03:06 PM   #2
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Sounds like the AF motor in your camera might be broken, or perhaps the AF drive shaft. Can you hear the motor spinning, or do you see any evidence of physical damage to the drive shaft? I've heard of the spring breaking and the shaft therefore failing to extend.

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07-18-2018, 03:50 PM   #3
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QuoteOriginally posted by Adam Quote
Sounds like the AF motor in your camera might be broken, or perhaps the AF drive shaft. Can you hear the motor spinning, or do you see any evidence of physical damage to the drive shaft? I've heard of the spring breaking and the shaft therefore failing to extend.
I could hear the motor struggling to focus when I have the prime/constant F lenses. Not sure what the camera term is for the noise it makes when trying to focus is but I could hear the motor like it's trying to focus.
07-19-2018, 04:41 AM   #4
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I used the constant max aperture 16-45 zoom for a couple of years on a K-5 with no issues; sounds like something’s amiss.

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