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06-05-2019, 10:42 AM   #1
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Pixel shift calibration

My original K1 did pixel shift just fine, but somehow it develops some line patterns over the full area of the sensor, especially for exposures longer than a couple of seconds. I'm not sure what does that. When I got my K1 II pixel shift doesn't yield line patterns on long exposures like the K1 does. I once ran a sensor check and I could listen to noise sounding like small displacement of the sensor. So I was wondering if the sensor checks perform some pixel shift calibration or not, and haven't found anything relevant in the K1 manual. Any idea how to figure out if sensor check perform pixel shift calibration or not?

06-05-2019, 10:55 AM   #2
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Can you post a sample image with the problem?
06-05-2019, 12:50 PM - 1 Like   #3
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Digital sensors are prone to interference from EMF. Does the line pattern occur all the time or only when near potential EMF sources such as overhead powerlines/ operating microwaves, etc.?
06-05-2019, 01:16 PM   #4
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If the line patterns are in the brighter areas, then perhaps the lighting is changing during the multiple long exposures -- sunsets are terrible in this regard and many artificial light sources change brightness as the warm up. (You might examine the histograms of the four DNGs inside the big PS RAW file to see if anything is shifted.)

If the line patterns are in the darkest areas, perhaps the sensor is warming up (or cooling off) during the exposures. (You might try turning on long-shutter-time NR to see if that corrects the problem.)

06-05-2019, 01:54 PM   #5
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QuoteOriginally posted by biz-engineer Quote
Any idea how to figure out if sensor check perform pixel shift calibration or not?
What is "sensor check"? If you mean bad pixel mapping, I can add that my K-3 (no pixel shift) does a short burst of SR system noise when doing the pixel mapping.


Steve

Last edited by stevebrot; 06-05-2019 at 03:16 PM.
06-05-2019, 10:02 PM   #6
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QuoteOriginally posted by stevebrot Quote
What is "sensor check"? If you mean bad pixel mapping, I can add that my K-3 (no pixel shift) does a short burst of SR system noise when doing the pixel mapping.
Yes, when I wrote "sensor check", I meant pixel mapping. So if your K3 does some SR motion while pixel mapping, I'd invalidate the hypothesis of pixel shift calibration on my K1 during pixel mapping operation.

---------- Post added 06-06-19 at 07:05 ----------

QuoteOriginally posted by ProfessorBuzz Quote
Can you post a sample image with the problem?



I couldn't find the JPEG from pixel shift, I guess I've deleted the pixel shift version and exported to JPEG of a single frame / non-pixel shift exposure.

---------- Post added 06-06-19 at 07:07 ----------

QuoteOriginally posted by jbinpg Quote
Digital sensors are prone to interference from EMF. Does the line pattern occur all the time or only when near potential EMF sources such as overhead powerlines/ operating microwaves, etc.?
I would exclude EMI at the location, but we never know... there are so much electromagnetic waves going on these days... 5G will come it will be worse. I'd trust the EMI shielding of the Pentax camera for now.

---------- Post added 06-06-19 at 07:17 ----------

QuoteOriginally posted by photoptimist Quote
If the line patterns are in the brighter areas, then perhaps the lighting is changing during the multiple long exposures
I think you nailed it. According to the JPEG above, it was a 25 sec exposure at f11 after sunset (blue hour) (Date 2016:08:01, Time 21:16:29). And I remember that the line patterns were on the top part of the castle courtyard and the blue sky, the part of the frame that was mostly lit by natural light and not the light bulbs. I was surprise to get line patterns from the pixel shifted exposure because the tripod was sitting on the big stones of the castle floor and I used the IR remote to trigger the exposure. But, the exposure time was 25 sec. per frame, there was 75 sec. time difference between the 1st PS frame and the 4th PS frame, enough for the natural light to have slightly changed.
06-05-2019, 10:39 PM   #7
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QuoteOriginally posted by biz-engineer Quote
So if your K3 does some SR motion while pixel mapping
It sounds much the same as SR during live view.


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06-06-2019, 03:03 AM   #8
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QuoteOriginally posted by biz-engineer Quote
Yes, when I wrote "sensor check", I meant pixel mapping. So if your K3 does some SR motion while pixel mapping, I'd invalidate the hypothesis of pixel shift calibration on my K1 during pixel mapping operation.

---------- Post added 06-06-19 at 07:05 ----------





I couldn't find the JPEG from pixel shift, I guess I've deleted the pixel shift version and exported to JPEG of a single frame / non-pixel shift exposure.

---------- Post added 06-06-19 at 07:07 ----------


I would exclude EMI at the location, but we never know... there are so much electromagnetic waves going on these days... 5G will come it will be worse. I'd trust the EMI shielding of the Pentax camera for now.

---------- Post added 06-06-19 at 07:17 ----------


I think you nailed it. According to the JPEG above, it was a 25 sec exposure at f11 after sunset (blue hour) (Date 2016:08:01, Time 21:16:29). And I remember that the line patterns were on the top part of the castle courtyard and the blue sky, the part of the frame that was mostly lit by natural light and not the light bulbs. I was surprise to get line patterns from the pixel shifted exposure because the tripod was sitting on the big stones of the castle floor and I used the IR remote to trigger the exposure. But, the exposure time was 25 sec. per frame, there was 75 sec. time difference between the 1st PS frame and the 4th PS frame, enough for the natural light to have slightly changed.
Do you use Raw Therapee when developing your pixel shift images? Because there is a "equalize brightness of frames" button there in the pixel shift options that can help with some of those sorts of situations.

06-06-2019, 03:55 AM   #9
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Only way I have managed to get line or grid-patterns with PS is a situation where light changes during the exposure. Motion effects are different beast and very clear to spot (RawTherapee handles them fine). So far, my own results have been similar with K-1, K-1mk2 and KP.

Long exposure cancels out some light changes. For example 30 second PS exposure in ~stable candlelight results in mostly good outcome. But too short exposure in the same situation, like 5-10 seconds, gives 4 subframes with varied light levels -> grid pattern. Flickering flame is always a mess.
06-06-2019, 05:32 AM   #10
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QuoteOriginally posted by Rondec Quote
Do you use Raw Therapee when developing your pixel shift images? Because there is a "equalize brightness of frames" button there in the pixel shift options that can help with some of those sorts of situations.
I've used it a bit, but wasn't happy with colors. Too bad, RT has the best pixel shift processing functionality.
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