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02-12-2021, 07:33 AM - 1 Like   #16
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That looks like fixed-pattern read noise. The sensor or related electronics are introducing a false signal. All cameras experience it to some degree. Was it a hot day or was the camera sitting in the sun a long time?

As already mentioned, dark frames can help confirm the issue. Keep the lens cap on, have the camera in a darkened room or closet to avoid any light leaks around the lens mount or viewfinder, and take photos with multiple settings:
  • ISO 100, 1/320 second, the same settings as in your original photo.
  • ISO 1600, 1/320 second, to see how the noise change with ISO.
  • ISO 100, 30 seconds, to evaluate what happens with long exposures
  • ISO 1600, 30 seconds.
Push the brightness of the dark frames with photo software. Expect varying degrees of random static across the image, bright single-color hot pixels, faint lines like in your original sample, and maybe extra noise at one edge of the photo from amp glow.

I don't think it's a memory card issue. The lines would be more pronounced.

02-12-2021, 08:19 AM   #17
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QuoteOriginally posted by 35mmfilmfan Quote
Instead of PEF, have you thought of using DNG ? May be a conflict with your PP software.
The problem arises before postprocessing the images

---------- Post added 02-12-21 at 08:21 AM ----------

QuoteOriginally posted by DeadJohn Quote
That looks like fixed-pattern read noise. The sensor or related electronics are introducing a false signal. All cameras experience it to some degree. Was it a hot day or was the camera sitting in the sun a long time?

As already mentioned, dark frames can help confirm the issue. Keep the lens cap on, have the camera in a darkened room or closet to avoid any light leaks around the lens mount or viewfinder, and take photos with multiple settings:
  • ISO 100, 1/320 second, the same settings as in your original photo.
  • ISO 1600, 1/320 second, to see how the noise change with ISO.
  • ISO 100, 30 seconds, to evaluate what happens with long exposures
  • ISO 1600, 30 seconds.
Push the brightness of the dark frames with photo software. Expect varying degrees of random static across the image, bright single-color hot pixels, faint lines like in your original sample, and maybe extra noise at one edge of the photo from amp glow.

I don't think it's a memory card issue. The lines would be more pronounced.
Thanks, iīll try all of what you mention.

Regarding the shooting conditions, those were not especillay harsh, itīs winter time in Spain but not really cold
02-12-2021, 12:21 PM - 1 Like   #18
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Very odd. I can see the bands and maybe the lines on my phone but only after enlarging it. The enhanced line shot is easy to see as well
02-12-2021, 01:33 PM - 1 Like   #19
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I am thinking it may be some component starting to fail in the read out from the sensor. Possibly slightly higher resistance in a connection or a connection that has become marginal. Another guess I have may be marginal power so maybe try a new or different battery. Still another guess might be a problem with the analogue to digital converter possibly related to my previous 2 guesses. These are based off of just how regular the pattern is so it seems like a systematic error. Apart from a power issues where trying with a fresh battery and/or cleaning contacts I don't know what one would do to resolve the issue.

02-12-2021, 02:28 PM - 1 Like   #20
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QuoteOriginally posted by jllaurado Quote
a few days later i bought a grip for it and installed it right away, but not the original from Pentax.
Are you saying the grip is not the one made by Pentax for this camera model?

Being that the shutter release count is so low, and the camera is in mint shape, one would think it should function perfectly. But with a used camera, one never knows for sure what that sample has been through. Those grid lines are not normal, or we would have had many complaints from people about their K-7 cameras by now. It is rather too bad that you did not instead find a mint, low use K-5, or even better a K-5 II or K-5 IIs as the K-5 series, subsequent to the K-7, did represent a significant advancement in imaging quality including higher ISO performance.

Last edited by mikesbike; 02-12-2021 at 02:35 PM.
02-12-2021, 02:53 PM - 1 Like   #21
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QuoteOriginally posted by jllaurado Quote
Thanks, iīll try all of what you mention.
Regarding the shooting conditions, those were not especillay harsh, itīs winter time in Spain but not really cold
I was wondering if maybe the sensor was too hot but that doesn't seem to be your issue. Image sensor noise decreases with cold, gets worse with heat.

I'm surprised to see noise like that in a sunny blue sky at ISO 100 but I've never owned a K-7. Noise becomes more of an issue with astrophotography of very dim deep sky objects, extremely long exposures, or high ISO.

Here's another thread that shows an example of vertical noise on a K-7. Maybe your camera is sort of normal. Pentax k-7 low light banding - normal or worrying? - PentaxForums.com
02-12-2021, 04:27 PM - 1 Like   #22
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Here's some more analysis - gives some quantatative numbers, but I don't know what they mean! Maybe this will be useful to somebody who knows more about exactly how Pentax reads out the sensor values.

I used the ImageJ program (ImageJ ; I love this program!) to make cuts across the frame, to determine the spacing of the bands.

Here's a box drawn on the stretched image from TonyW. ImageJ averages the vertical data within the box and then draws an amplitude plot of the data values across the image.


And, here's the data plot:



Note the very regular spacing of the peaks. The spacing is 60 pixels, except for a few extra lines near the beginning and end of the frame.

And here is a "zoom" into part of the frame:


and the corresponding plot:


There is a definite width to the bands, typically 3-4 pixels or so at half-width, except that the second band from the right side is about twice as wide.

What does it mean? I don't know! I suspect some kind of regular glitch in the data read out system.
02-12-2021, 06:25 PM   #23
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And a bit more data.

Here's a plot of the data values from the original file of jlaurado, in a zoomed in area of the frame:



The higher amplitude (is this a clue?) is only about 1.5 data values out of 70 or so, at the peak, and less otherwise - so the effect of the banding is only to increase the level of the pixel data by 2 or 3 percent at most. I wonder if some bit(s) in the readout is/are being affected. It's clearly not just every 60th bit, though, given the width of the affected data.

Remember that data readout from a CCD/CMOS (not sure which the K7 has) involves shifting the data from an image line out to the A/D converter and then shifting the data down a row for the next readout (as my astronomer wife, who is a Co-PI on a Hubble Space Telescope instrument reminded me). There's a lot can get messed up here, but why it is so systematic must be telling us something.

02-13-2021, 03:57 AM - 1 Like   #24
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There was a forum member (for 2 posts only!) that had what appears to be the same issues. Unfortunately he never came back so we do not know the outcome.

Thin white vertical lines in photos - PentaxForums.com

However he did post to Flickr maybe he is still active there and you could message him?


Just taken two sections of two different images and manipulated in PS clearly demonstrates a vertical line issue even with what appears to be images that are not underexposed. Link to one of the images
Alligator | Photographed at Pelican Island Festival, Sebasti? | Flickr
https://www.flickr.com/photos/gregharber/5541180718/
Attached Images
 
02-13-2021, 04:51 AM   #25
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QuoteOriginally posted by AstroDave Quote
Here's some more analysis - gives some quantatative numbers, but I don't know what they mean! Maybe this will be useful to somebody who knows more about exactly how Pentax reads out the sensor values.

I used the ImageJ program (ImageJ ; I love this program!) to make cuts across the frame, to determine the spacing of the bands.

Here's a box drawn on the stretched image from TonyW. ImageJ averages the vertical data within the box and then draws an amplitude plot of the data values across the image.


And, here's the data plot:



Note the very regular spacing of the peaks. The spacing is 60 pixels, except for a few extra lines near the beginning and end of the frame.

And here is a "zoom" into part of the frame:


and the corresponding plot:


There is a definite width to the bands, typically 3-4 pixels or so at half-width, except that the second band from the right side is about twice as wide.

What does it mean? I don't know! I suspect some kind of regular glitch in the data read out system.
Thatīs an outstanding analysis, many thanks

---------- Post added 02-13-21 at 04:59 AM ----------

QuoteOriginally posted by TonyW Quote
There was a forum member (for 2 posts only!) that had what appears to be the same issues. Unfortunately he never came back so we do not know the outcome.

Thin white vertical lines in photos - PentaxForums.com

However he did post to Flickr maybe he is still active there and you could message him?


Just taken two sections of two different images and manipulated in PS clearly demonstrates a vertical line issue even with what appears to be images that are not underexposed. Link to one of the images
Alligator | Photographed at Pelican Island Festival, Sebasti? | Flickr
Salvia | Salvia blossom. | gharber | Flickr
Thanks, iīll do that.

Just came home from a photowalk to test if the grip (now unattached) was at fault, unluckily the lines remain, but now have also noticed that the lines follow a constant "path", if i turn the camera to take a vertical pic, the lines become horizontal, whatever that may mean, possibly related to the output from the sensor.

Iīm going to try what i was advised before, to take totally black images (with the cap) at different values., Iīll also change the SD and recharge the battery for more tests.


Guys, you are all amazing, many thanks for all the help received, whatever the problem is.

Last edited by jllaurado; 02-13-2021 at 05:00 AM.
02-13-2021, 05:10 AM   #26
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Someone else had the same issue.
https://www.pentaxuser.com/forum/topic/problems-with-k--7-21524

02-13-2021, 06:54 AM - 1 Like   #27
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I would try the following:

- Different SD-card
- Reset via PK Trigger Cord:
pkTriggerCord
pkTriggerCord | Tethering Software for DSLR Cameras

If this does not help, then I guess its the sensor.
02-13-2021, 12:32 PM - 1 Like   #28
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Search for "fixed pattern noise" and you'll find a lot more information. It is a sensor hardware issue frequently encountered when doing long exposure astrophotography.


Anecdotally, from other threads here, it seems like the K-7 is more prone to these vertical stripes than other Pentax models, but it doesn't seem to be a problem with every K-7.
  • Maybe some K-7 sensors came from a bad batch.
  • Maybe the early K-7 sensor design was known to have vertical stripes, and the sensor manufacturer or Pentax added something to reduce the stripes. That theoretical stripe reduction might fail over time.
If some component is marginal, it could show up some times and not others depending on temperature, battery voltage, or other factors.
02-13-2021, 12:55 PM - 1 Like   #29
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I fear the only hope here is to re-install the firmware and see if that helps.

If not it seems like a hardware issue which would be uneconomic to fix.
02-13-2021, 02:20 PM - 1 Like   #30
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QuoteOriginally posted by jllaurado Quote
Hello everyone,

Iīd appreciate some help with a problem of vertical pattern lines that show in my images even at base ISO. See example below.

Iīm very new to Pentax, got a K-m a few months ago and was so happy with it that recently i bought a K-7 to keep experiencing with the brand in order to decide if i wanted to move completely to this system.
Of course it was a used model, and when i met the previous owner i tested the camera and everything seemed to go well. I didnīt use the camera for some days due to lack of time and a few days later i bought a grip for it and installed it right away, but not the original from Pentax.
I went out to test the camera for a whole day and i begun finding many problems that got me worried, very underexposed images, lots of incredible noise ruining the shot at base ISO in the middle of the day, and many other problems that were not constant, as some shots came out nice. Let me add that i did install the battery in the grip, not in the camera body (this might be important, though at that time i didnīt know).

I found some adjustments in the menus from the previous owner that i didnīt like so i decided to reset the camera to see if those might be the cause of the problems, and at the same time moved the battery from the grip to the body (still unaware if this might be important).

Last night i found some posts here (related to the K-10D) in relation to that old VPN problem saying that the grip might cause electric interferences and those might show in the image, but my camera is not a K-10D but a K-7. Iīve since tested the camera and the underexposed thing and crazy noise seems to be gone, but now i find those vertical lines showing up in many images, not really very visible unless you zoom in, but i guess those should not be there.

Now that i learnt on the possible grip problems Iīll try over the weekend by removing the grip and see if thereīs some improvement, but in the meantime iīd appreciate some input on other possible causes of this, or if someone else has experienced this.

Iīm still not sure if this problem is that banding shown in images with that VPN problem.
The camera has the original battery, still holding charge very well, and the lens used is the kit one, 18-55 WR, and i shoot RAW+ (PEF) and Manual mode always.


The cropped test image showing the problem, a shot of the sky so itīs easier to see:


Thanks
If it happens on every image, I don't have an answer beyond some sort of sensor failure.
However, I have seen that from time to time on shots similar to yours (sky and not much else). This was explained to me by someone with a physics background as quantization errors during demosaicing the image.
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