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08-16-2009, 09:36 AM   #1
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Problem with my K20D sensor?

I posted this on DPR but, since I didn't profess to sell my Pentax gear due to its inferiority, I did not get any attention. I've also emailed Pentax support in the mean time but probably won't get an answer until Monday the earliest. Anyhow, here it goes...

I was trying to set the UniWB on my K20 following Thomas' (Duplo's) advice in

Re: dcraw -> UniWB? How?: Pentax SLR Talk Forum: Digital Photography Review

and noticed that, even when setting very long exposures that should have blown all the pixels on the sensor, the upper right corner always has unblown pixels. Can anyone else see this on their camera?

I've uploaded such a PEF at

http://cid-01c9e22210909a2e.skydrive.live.com/self.aspx/.Public/K20D0529.PEF

It was exposed for 8 seconds at f/1.4. Both the in-camera and the LR blinkies show that a whole bunch of pixels in the upper right corner are not blown out.

Any thoughts? Do I need to send the camera in?

Thanks,
Nick


Last edited by savoiu; 08-16-2009 at 09:37 AM. Reason: SkyDrive URL got chopped
08-16-2009, 10:59 AM   #2
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QuoteOriginally posted by savoiu Quote
I posted this on DPR but, since I didn't profess to sell my Pentax gear due to its inferiority, I did not get any attention. I've also emailed Pentax support in the mean time but probably won't get an answer until Monday the earliest. Anyhow, here it goes...

I was trying to set the UniWB on my K20 following Thomas' (Duplo's) advice in

Re: dcraw -> UniWB? How?: Pentax SLR Talk Forum: Digital Photography Review

and noticed that, even when setting very long exposures that should have blown all the pixels on the sensor, the upper right corner always has unblown pixels. Can anyone else see this on their camera?

I've uploaded such a PEF at

K20D0529.PEF - Windows Live

It was exposed for 8 seconds at f/1.4. Both the in-camera and the LR blinkies show that a whole bunch of pixels in the upper right corner are not blown out.

Any thoughts? Do I need to send the camera in?

Thanks,
Nick
no answer to that problem but just shoot the "test target"and use that. It will get your multipliers close to 1:1:1

GUILLERMO LUIJK >> TUTORIALS >> UNIWB. MAKE CAMERA DISPLAY RELIABLE
Create a image in sRGB w/ the following color values:
R=162, G=64 y B=104
BTW: Could be shaded due to lens vignetting so it's not blowing out.
08-16-2009, 01:01 PM   #3
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Thanks Jeff. Thomas' recipe is faster and results in exactly 1,1,1,1 multipliers.

I'm still wondering about the sensor. What does your camera do in the same situation? Do all your pixels get blown out?
08-16-2009, 01:20 PM   #4
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QuoteOriginally posted by jeffkrol Quote
BTW: Could be shaded due to lens vignetting so it's not blowing out.
Just saw this part. I thought of that too. But then the unblown pixels would follow a vignette pattern rather than being just in the upper right corner. I've tried other lenses as well and still the unblown area is the same.

08-17-2009, 07:40 PM   #5
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I guess not much better response than on DPR. I must be doing something wrong...
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