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04-30-2008, 08:20 AM   #1
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K10D hot/stuck pixels

Hi!

Just got the shots from my last K10D session -- all images are affected by a single hot/stuck pixel (looks like a pink cross with white pixel in the middle). Then I tried to produce a darkframe at ISO100 1" to 6" -- no traces of problem! How can that be?


Thanks!

04-30-2008, 03:39 PM   #2
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Quick quesses.
1. First shot was at high ISO ie 1600, 3200 but latest shots were at 200
2. First shots were in RAW but second series were in JPG (hot pixels in RAW once processed in JPG may get removed/smoothed out in the compression process.
3. Exposure times - longer on first series vs shorter on second batch.
4. And getting into the techie stuff... if the camera operating temp/sensor temp is hotter may see increased noise - perhaps first series camera had been on for awhile/warmer environment vs second batch taken with a "colder" camera ie on start up. I thought the temp was in EXIF but quickly checked PhotoME and didn't see it. I believe some high end CCD/software does show the temp for astronomy. Hope this helps. Ken.
04-30-2008, 03:49 PM   #3
baw
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QuoteOriginally posted by tdb Quote
Hi!

Just got the shots from my last K10D session -- all images are affected by a single hot/stuck pixel (looks like a pink cross with white pixel in the middle). Then I tried to produce a darkframe at ISO100 1" to 6" -- no traces of problem! How can that be?


Thanks!
Probably noise reduction kicking in. Camera makes a second dark exposure, and removes the noise and hot pixels in that one from the original exposure.
04-30-2008, 05:08 PM   #4
tdb
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QuoteOriginally posted by baw Quote
Probably noise reduction kicking in. Camera makes a second dark exposure, and removes the noise and hot pixels in that one from the original exposure.
Never heard of K10D doing in-camera dark frame subtraction... Is there such a feature really?

04-30-2008, 06:33 PM   #5
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QuoteOriginally posted by tdb Quote
Never heard of K10D doing in-camera dark frame subtraction... Is there such a feature really?
Absolutely. There is a menu option for "NR" or Noise Reduction which is dark frame subtraction. On the "older" cameras like my K1x0Ds the NR kicks in only on longer exposures when enabled which is the default if you have not discovered the option yet. I turn it off for situations like fireworks when the exposures are say 2 seconds and I don't want the 2 seconds dead time as the camera takes a dark frame to subtract. Otherwise, I leave it on all the time. Really does a great job on astrophotos. I believe the K10D handles NR like my camera. There has been some debate by the K20D owners as to whether they have complete control of NR.
05-01-2008, 04:50 AM   #6
tdb
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QuoteOriginally posted by LeoTaylor Quote
Absolutely. There is a menu option for "NR" or Noise Reduction which is dark frame subtraction. On the "older" cameras like my K1x0Ds the NR kicks in only on longer exposures when enabled which is the default if you have not discovered the option yet. I turn it off for situations like fireworks when the exposures are say 2 seconds and I don't want the 2 seconds dead time as the camera takes a dark frame to subtract. Otherwise, I leave it on all the time. Really does a great job on astrophotos. I believe the K10D handles NR like my camera. There has been some debate by the K20D owners as to whether they have complete control of NR.
You are right!!! Thanks!
I just made a 1"@ISO100 darkframe and found 5 pixels with abnormally high values in one/two channels. One of them turned out to be the one that was spoiling my pictures. I mapped them out with dcraw as dead -- problem solved.
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