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08-04-2010, 01:08 PM   #1
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K20D - Bad Sensor (Banding?)

I am looking for some assistance with my K20D. It is 3 months out of warranty (go figure) so I am looking for some input from the experts and enthusiasts here. In the past week, I have noticed some discoloration in my images -- consistently on the left side of the image where the image is darkened. Some details that I think would be useful to know:
1) The problem occurs on various lenses
2) The problem cannot be seen via the viewfinder.
3) It is observed when using the live view (open shutter).
4) I have tried various ISO / apertures / focal lengths
5) The problem is observed most in darker scenarios, but does exist in well lit settings.

I have included two images below of a wall in my house (with and without flash). The wall is a solid color (light blue). The problem is observed by noting the vertical divider (a horizontal gradient) to the right of center.

I am thinking I am looking at a sensor that needs to be replaced, but I am looking for opinions, information on if this is common (or even has a term), ideas on how to correct this problem, or a confirmation on my sensor thought. This problem does not seem consistent with dirt/dust dark spots, but I have not ruled that out with a cleaning yet.

Thanks in advance for any assistance and taking the time to read this post.

-James

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08-04-2010, 03:16 PM   #2
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thats pretty ugly.

can you see anything on the sensor itself? hopefully it can be (carefully) washed off.
08-04-2010, 03:30 PM   #3
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Just make several shots in manual with the lenscap on.
1/1000 to 1 sec at 100 iso or something like that, you will probably see a similar banding independend of shuttertime.
It is possible that this can be calibrated out by pentax service.
08-04-2010, 04:02 PM   #4
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I have seen that greenish pink banding in different forms before. Once on a Canon point and shoot that I replaced and on my K10D where the camera was under extended warranty. On my K10D they replaced the sensor. It looks to me that that sensor is going bad. You may want to check with pentax to see if you can get an extended warranty. I know that with the K-7 you can get an extended 2-year warranty for free if you contact pentax.

08-04-2010, 07:38 PM   #5
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Any chance that this is the result of the natural color cycling of fluorescent lighting? Do a Google search to see how this manifests itself.
08-05-2010, 01:02 AM   #6
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QuoteOriginally posted by Marc Sabatella Quote
Any chance that this is the result of the natural color cycling of fluorescent lighting? Do a Google search to see how this manifests itself.
I think it is unlikely he has a K20D with horizontal running shutter.

Just do the test with the lenscap on, I had a similar problem when my K20D came back from repair.
They could fix that with a second repair, they probably did not redo a sensor calibration after replacing some parts.
08-05-2010, 03:54 AM   #7
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Thanks everyone for the feedback and input. Some response:

paperbag846:
I see nothing on the sensor itself -- but that is not to say minor moisture or something is not there. Given it's perfect vertical stature, I am guessing it is not something on the sensor. If I feel up to it, I'll give it a cleaning this weekend.

glasback:
I did some more additional testing and I found the banding does seem independent of the shutter time (Hind sight, I suppose this is why I could see it in live view). I took pictures with the lens cap on at 100 ISO as suggested, but the pictures came out pure black with no banding. Is this what you would have expected or were you expecting the picture to be banded with the lens cap on?

Eric Seavey:
You are suggesting where I was with the bad sensor. Not what I wanted to hear, but I am happy to know that Pentax might have promising customer support and extend or repair the camera for free (reduced cost would be great too!). I will contact them in the next few days and see what they can do to help out.

Marc Sabatella:
Unfortunately it is not a fluorescent light problem as it is observed in my outdoor pictures as well...I first observed the problem when I was in northern Michigan taking pictures of waterfalls. Great idea though as I was not aware of color cycling.
08-05-2010, 04:25 AM   #8
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QuoteOriginally posted by JamesToyski Quote
I did some more additional testing and I found the banding does seem independent of the shutter time (Hind sight, I suppose this is why I could see it in live view). I took pictures with the lens cap on at 100 ISO as suggested, but the pictures came out pure black with no banding. Is this what you would have expected or were you expecting the picture to be banded with the lens cap on?
If you strecht the histogram (best do this with RAW PEF files), you will probably see the same pattern emerging, regardless the shuttertime.
I think it is the response, which the sensor gives without any exposure.

08-05-2010, 05:53 AM   #9
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QuoteOriginally posted by glasbak Quote
If you strecht the histogram (best do this with RAW PEF files), you will probably see the same pattern emerging, regardless the shuttertime.
I think it is the response, which the sensor gives without any exposure.
Thanks for the additional detail -- I will give it a go this evening. If I am unable to determine it, I will post the RAW files if you are willing and able to take a peek.

Thanks!
08-11-2010, 05:42 AM   #10
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QuoteOriginally posted by glasbak Quote
If you strecht the histogram (best do this with RAW PEF files), you will probably see the same pattern emerging, regardless the shuttertime.
I think it is the response, which the sensor gives without any exposure.
glasbak -- Bingo! (sorry for the delay of this response). The sensor is indeed still giving a response, regardless of the shutter time. The very far left R/G/B is 9/2/6 and approaches the anticipated 0/0/0 near the center.

Is this fixed only by a sensor replacement or is there a way I can recalibrate/zero the sensor to reset it?

Thanks again!
08-15-2010, 10:49 PM   #11
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QuoteOriginally posted by JamesToyski Quote
glasbak -- Bingo! (sorry for the delay of this response). The sensor is indeed still giving a response, regardless of the shutter time. The very far left R/G/B is 9/2/6 and approaches the anticipated 0/0/0 near the center.

Is this fixed only by a sensor replacement or is there a way I can recalibrate/zero the sensor to reset it?

Thanks again!
Hi,
another late reaction
The sensor problem is something they 'fixed' for my k20d at the Pentax service department.
Probably a calibration not available for end users.
Send an e-mail with an explanation of your problem to the pentax service department of your country to know what it will cost.
06-27-2012, 12:56 AM   #12
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Hello.

I have just the same problem and have tested the same as you, Can you please tell me the solution to the problem, was it calibration or change of the sensor or anything else.
Thank you.
07-03-2012, 01:15 PM   #13
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Sorry for the delay. I sent it in for warranty repair (covered by my CC provider -- thanks Citibank. Sorry for the shameless plug.) They ended up replacing the sensor all together. It has been working fine since. I hope you have good luck finding a solution or servicing it!
07-03-2012, 02:57 PM   #14
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Thanks for the reply, I have just delivered it to service, I hope I get it on extended warrenty, if else I think I will not repair it.
I have seen that it will cost around 700$ to repair in Norway.

Best regards
André
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