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08-10-2019, 08:07 PM   #1
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Pentax 24-70 lens problem with extreme clipping to the right

The last few weeks my Pentax 24-70 clips extremely to the right with any setting higher than 5.6 aperture even at exposure compensation at -5, and ISO 100. I have a k1, and other Pentax lenses that I have tried on the K1 with no problems so I've narrowed it down to the 24-70.

08-10-2019, 08:27 PM   #2
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QuoteOriginally posted by k2parn Quote
Pentax 24-70 lens problem with extreme clipping to the right
Lenses don't clip, though they might have a lazy or sticky aperture mechanism. With the lens off the camera, examine the aperture opening while operating the aperture actuator lever by hand, first by flicking from its smallest opening and then by releasing from its wide open position. In both cases the action should be snappy without hesitation.

Question: What exposure mode is this happening in and what meter configuration (matrix, center-weighted, or spot) are you using?


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08-10-2019, 10:31 PM   #3
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Please post some sample images with EXIF details included.
08-11-2019, 02:32 AM   #4
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As Steve says, lenses don't clip. They can have sticky aperture blades or be decentered, but post some images that show the problem.

08-11-2019, 03:35 AM   #5
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QuoteOriginally posted by k2parn Quote
The last few weeks my Pentax 24-70 clips extremely to the right with any setting higher than 5.6 aperture even at exposure compensation at -5, and ISO 100. I have a k1, and other Pentax lenses that I have tried on the K1 with no problems so I've narrowed it down to the 24-70.
The first image settings were ISO 140, F/8, 1/180 at 24mm
The second image settings were ISO 200, F/16, 1/160 at 70mm
They were taken in aperture priority, and matrix metering,
I'm planning to check for sticky aperture blades later today, and I appreciate the help.
Attached Images
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PENTAX K-1  Photo 
View Picture EXIF
PENTAX K-1  Photo 
08-11-2019, 04:35 AM   #6
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It's interesting that the EXIF for the second image, which is of course dramatically overexposed, does not include anything about exposure bias, while the first one does (-0.5EV).

I tend to use centre weighted metering, and expose for the brighter parts of the image. I'd much rather push shadows than pull highlights. These are rather extreme though, so I'd be interested to learn of your results checking the aperture.
08-11-2019, 05:49 AM   #7
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The camera is way over exposing for the situation. Not sure why that is, but maybe some problem with the aperture mechanism (although that typically gives darker images in my experience).
08-11-2019, 05:59 AM   #8
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QuoteOriginally posted by Rondec Quote
The camera is way over exposing for the situation. Not sure why that is, but maybe some problem with the aperture mechanism (although that typically gives darker images in my experience).
Sticky apertures do not stop down enough and therefore overexpose - so this could well be the problem, as others have said

08-11-2019, 06:06 AM   #9
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Clean the contact on the lens mount.
08-11-2019, 06:57 AM   #10
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Well, I think I have discovered the issue because when I checked the aperture blades with the lens off, the aperture blades do not close automatically any more except manually so my 3 year old lens needs repair it looks like. Thank you for helping find the culprit!
08-11-2019, 01:49 PM   #11
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QuoteOriginally posted by Rondec Quote
The camera is way over exposing for the situation. Not sure why that is, but maybe some problem with the aperture mechanism (although that typically gives darker images in my experience).
The EXIF indicates a reasonable metered EV. I suspect a problem with the lens aperture mechanism or the camera is failing to stop down the lens for the exposure.


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08-11-2019, 01:51 PM   #12
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QuoteOriginally posted by k2parn Quote
Well, I think I have discovered the issue because when I checked the aperture blades with the lens off, the aperture blades do not close automatically any more except manually so my 3 year old lens needs repair it looks like. Thank you for helping find the culprit!
Are you saying that it does not stop down when the lens is attached to the camera?


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08-13-2019, 02:04 PM   #13
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Yes, the aperture blades do not open or close manually, and I can only get images at 5.6 or larger without being totally blown out, so I shipped it off for repair yesterday.
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