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10-28-2009, 02:55 PM   #1
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K100D how many bad pixels are acceptable?

I read the other very recent thread by -Joe- about stuck pixels on his K100D sensor and it was a timely thread. Right after buying the camera used with about 3000 clicks I started noticing a few (like 3 - 5) bad pixels shooting jpg on normal exposures from 1/60th and faster, I would see them mainly when I would be zoomed in to do some editing, so I tried sensor cleaning via blower to no improvement and decided I had a few bad pixels. So I started shooting RAW and letting Lightroom "map" out the bad ones in conversion, but I really would rather use jpg and get more shots per card.

As time went on it seems I was seeing more and more specks any time I switched over from RAW to jpeg, and even when I would load RAWs into Lightroom, there's that moment while its doing the conversion that I think you briefly see the embedded jpg in the RAW file where I'd see a lots of spots and then they'd disappear.

I followed the suggestion of one poster in that thread to try a method from a dpreview forum on a Canon camera - to trip sensor cleaning mode with lens on followed by a reset. Then I put the lens cap on, threw it out of focus, went into a dark room and shot a couple jpgs, loaded them into Lightroom and saw a ton of specks (as in closer to 100)

Did I do the test right? should I have limited the shutter speed more? I know long exposures bring out more hot pixels which are not really bad/dead/stuck pixels, but this was not that long (1/3 sec)- I thought this is more like multi second exposures that show more hot pixels. Would it matter what ISO I used?


Last edited by F8&Bthere; 10-28-2009 at 03:42 PM.
10-28-2009, 03:19 PM   #2
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okay well i found a utility that tests for bad pixels, followed the instructions and was okay at 1/30, 1/15, 1/3, but when I hit 1 second it shot up to 60 hot pixels reported but still 0 dead. So I'm thinking that I'm okay for most shooting situations. But is 60 roughly normal at 1 second exposure? I swear I had tested some months ago (it's my 2nd camera, I don't use it all that often) and found that it had several actual stuck pixels at normal shutter speeds, so either I'm losing my mind or that reset method I tried actually worked... that is if I assume the deadpixeltest program is a reliable method and I executed it correctly.

Last edited by F8&Bthere; 10-28-2009 at 03:50 PM.
10-28-2009, 03:41 PM   #3
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Yes. This is what dark frame subtraction fixes..
10-28-2009, 03:51 PM   #4
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QuoteOriginally posted by F8&Bthere Quote
okay well i found a utility that tests for bad pixels, followed the instructions and was okay at 1/30, 1/15, 1/3, but when I hit 1 second it shot up to 60 hot pixels reported but still 0 dead. So I'm thinking that I'm okay for most shooting situations. But is 60 roughly normal at 1 second exposure? I swear I had tested some months ago (it's my 2nd camera, I don't use it all that often) and found that it had several actual stuck pixels at normal shutter speeds, so either I'm losing my mind or that reset method I tried actually worked... that is if I assume the deadpixeltest program is a reliable method and I executed it correctly.
What utility was that?

10-28-2009, 04:19 PM   #5
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QuoteOriginally posted by -Joe- Quote
What utility was that?
StarZen Technologies, Inc; DataFlex tools and books
10-28-2009, 05:46 PM   #6
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Mine only show up when actually taking a picture, with the lens cap on I get none.

From what I have read:

Dead pixel will be black, stuck pixel will be red/green or blue and a hot pixel will be white.
10-28-2009, 07:17 PM   #7
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During long exposures, you may get Noisy pixels which get stuck on some arbitrary signal output but behave normally for short exposures. I've seen many, more than a dozen of, them pop up during really long exposures but they don't worry me, because they just go back to normal for hand-held shots.

That's a different matter from true Hot/Stuck pixels which appear regardless of exposure time. Bad pixels are completely dark, like a tiny hole in your photograph.

My K100D had something like 3 or 4 Stuck pixels after 2 years of heavy use. So far, none on the K-7.
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