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08-02-2013, 10:14 AM   #1
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Sigma 8-16 problem

After a couple of shots K-30 "semi-freezes", it still measures and releases, but it does not answer to wheels/parameter change. The pictures during that "semi-freeze" have a spherical vignetting border at the frame top (I will post samples here later). Also the images are not properly tagged for orientation when reviewed.

Only way to restore normal operation is through off/on, yet after 10-15 shots the problem returns. I have tried different SD-cards and power sources and I believe the reason is the Sigma 8-16 lens. This is my only SDM-lens and the only one that causes trouble. Does anyone have similar experiences?

08-02-2013, 11:45 AM   #2
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I would check to see if all the contacts are clean. I have one and it's never done anything like that. I know my K5 has had issues with the proper focal length on 10mm or less in the past, so have you checked to see if zooming will make a difference?
08-05-2013, 09:46 AM   #3
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QuoteOriginally posted by VoiceOfReason Quote
I would check to see if all the contacts are clean. I have one and it's never done anything like that. I know my K5 has had issues with the proper focal length on 10mm or less in the past, so have you checked to see if zooming will make a difference?
Camera & lens contacts are clean, both are nearly new. The "semi-freeze" phenomenon comes at various zoom seeting, so I suppose it has nothing to do with that. Focal lengths under 10mm are simply not recorded in the EXIF for this lens, but I can live with it.

I suspect the freezing has something to do with AF-operation, in particular with the way how camera/lens communicate. When I use MF with this Sigma lens the freezing is absent. No other lens (all Pentax) gives me any problems.
08-05-2013, 10:45 AM   #4
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Are you able to get your hands on any other HSM lenses or any Pentax lenses with the DC or SDM autofocus? If they act the same way, then it's the camera, if not, then definitely the lens. If it is the lesn I would definitely have it checked out because it is a fun lens.

08-09-2013, 08:51 AM   #5
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sample photos











I have been able to track this problem down: it only appears on K-30 with Li-Ion but not when running on Eneloop-power. Interestingly it does not appear on K-r with the same power source and it is totally absent on the K-20 though.
08-09-2013, 09:25 AM   #6
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Perhaps the Sigma HSM takes a lot more power than the Li-Ion can muster and the battery voltage falls, causing mayhem. The images perhaps look like the mirror hasn't completely cleared the light path from lens to sensor or is still moving (i.e. it's slow) while the shutter is operating. All guesswork of course.
08-09-2013, 09:34 AM   #7
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Just to say that I use this combo without any problem for the moment.
I'm using the original battery and a Chinese one.
08-13-2013, 02:40 AM   #8
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I've done further examination and could reduce my K-30 problem down to a single Li-Ion battery. I have two original and 4 no name equivalents, the one that causes trouble is one of the Pentax originals. The marked battery works well with all my other genuine Pentax lenses except with the Sigma 8-16. Curiously the same battery works on K-r with the 8-16. Go figure. I suppose it has something to do with battery voltage and/or K-30 sensitivity to voltage levels.

08-13-2013, 02:53 AM   #9
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Vignetting looks like the built in lens hood getting in the frame !

Ronnie
08-13-2013, 03:55 AM   #10
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These are un-cropped frames from my sigma 8-16mm f/4.5-5.6 at the 8mm setting on a Pentax K5IIs with HSM in use. There is clearly something wrong with your lens, the lens hood shouldn't be visible at all in the image. I think there is a distinct possibility that the optics are de-centered* and the lens information contacts could be also misaligned - this would explain the intermittent AF and lens/body communication issues.





Also it is perfectly normal for Pentax DSLRs to not have the 8mm setting recorded in the EXIF....annoying, but normal for this lens.

*I went through several different copies of the Sigma 8-16mm to find the one I currently work with, Sigma actually sent me a letter with the final lens they sent to me stating that it was certified by their technicians to be free of defects.

Last edited by Digitalis; 08-13-2013 at 04:06 AM.
08-15-2013, 12:25 AM   #11
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Digitalis, how do you explain that the lens is working good with the other two cameras, K-20 & K-r? I figure this problem is K-30 specific and depends on certain battery voltage.
08-15-2013, 05:51 AM   #12
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Is your K-30 sensor somehow not centered. Maybe at one end of the SR travel ?

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08-16-2013, 12:07 AM   #13
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QuoteOriginally posted by ronnies Quote
Is your K-30 sensor somehow not centered. Maybe at one end of the SR travel ?

Ronnie
Maybe my description of what's happening was not detailed enough: so called "semi-freeze" makes the camera limited in respone: it still does AF, measures and releases. But it does NOT react to control wheels and/or any other button than the shutter release button. The pictures are saved to the card alright but they get the lens shade vignetting (see samples above).

The most obvious explanation to me is that the sensor gets locked in the upper right corner of its magnetic travel. The lens works flawless with my other two Pentax cameras.
08-16-2013, 01:42 AM   #14
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QuoteOriginally posted by dragra Quote
The most obvious explanation to me is that the sensor gets locked in the upper right corner of its magnetic travel. The lens works flawless with my other two Pentax cameras.
Have you got the "Composition Adjustment" set to on? Might not show up on other lenses. Could explain the hood showing.

Ronnie
08-16-2013, 02:57 AM   #15
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QuoteOriginally posted by dragra Quote
The most obvious explanation to me is that the sensor gets locked in the upper right corner of its magnetic travel. The lens works flawless with my other two Pentax cameras.
A most unusual issue - but not at all unsurprising considering you are using a 3rd party lens, some Canon and Nikon DSLR cameras get some strange problems with they are used with off brand lenses.
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