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10-21-2019, 07:22 AM   #1
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Aperture problems with Pentax 18-250 and K20D

I have a problem with my K20D and the Pentax 18-250. The lens aperture does not stop down when taking a photo. It has never corrected itself. The aperture works when you push the lever on the base of the lens manually but stays wide open when you take a photo in all modes. I have ried everything I can think of. I have also tried the camera with another lens and it works fine. I have tried the lens with another K20D and it has the same problems. So I believe the problem is with the lens. Any thoughts?


Read more at: K20d strange behavior - PentaxForums.com

10-21-2019, 07:27 AM   #2
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can you post a photo here, with EXIF data attached, please?
10-21-2019, 07:31 AM   #3
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QuoteOriginally posted by Wazza Quote
So I believe the problem is with the lens. Any thoughts?
Your logic is sound. The question I would ask is whether your camera detects the lens as being one it can control aperture on. Do you see "F--" in the viewfinder and other displays rather than an aperture number? Referring to the thread you linked to (and the duplicate post there), the next question is whether AF is also failing.


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10-21-2019, 07:34 AM - 1 Like   #4
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That sounds like a broken spring, broken aperture linkage, or sticky aperture in the lens.

Try this:
1) With the lens NOT on the camera, the aperture should be closed all the way down. (If this isn't true, the spring is probably broken)
2) If you push the aperture lever with your finger, the aperture should open up. (If this doesn't happen, aperture linkage is probably broken)
3) If you then take your finger off the aperture lever, it should quickly snap closed. (If the aperture slowly closes, the blades are probably sticky. If it doesn't close it might be a broken/stretched spring)

10-21-2019, 07:35 AM   #5
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Do you have another body (not a K20D) to try your lens on? Is AF working? Otherwise it seems that the electronic communication between body and lens is jammed, try cleaning pins in the lens mount part.
10-21-2019, 07:43 AM - 1 Like   #6
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Almost certainly a problem of the lens itself, particular as with another K20D.

This became clear when you asked this question a year ago!
10-21-2019, 07:51 AM   #7
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QuoteOriginally posted by photogem Quote
Almost certainly a problem of the lens itself, particular as with another K20D.

This became clear when you asked this question a year ago!


I thought this sounded familiar...
10-21-2019, 09:53 AM - 1 Like   #8
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QuoteOriginally posted by photogem Quote
Almost certainly a problem of the lens itself, particular as with another K20D.

This became clear when you asked this question a year ago!
QuoteOriginally posted by pepperberry farm Quote
I thought this sounded familiar...
I suspect a problem with the lens mount contacts or their wiring in the lens. AF is probably failing too (or at least it should be).


Steve

10-22-2019, 04:07 AM - 2 Likes   #9
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Looks like we might have to wait until next year to hear from the OP.
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