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02-18-2011, 04:30 PM   #1
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Is this a dirty sensor?

I took a few night shots yesterday and when I loaded them up on my PC I discovered a lot of blue, green and red dots in my photos.

They seem to be in the same position every shot so I've ruled out strange reflections and I've also since tried a different lens and gotten the same dots. But I can only see them in dark photos using a long exposure.

The strange thing is, I thought dirt on the sensor should show up as darks spots, not bright lights. I'm hoping there's not something wrong with the sensor...

I've attached an example below, any help identifying the problem and how to fix it would be greatly appreciated!

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02-18-2011, 04:35 PM - 2 Likes   #2
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Those are hot pixels. What camera do you have? If your camera supports it, running pixel mapping should correct those, or at least prevent them from doing that.
02-18-2011, 04:50 PM   #3
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QuoteOriginally posted by GregK8 Quote
Those are hot pixels. What camera do you have? If your camera supports it, running pixel mapping should correct those, or at least prevent them from doing that.
Thanks GregK8!

It's a K7. I've just run pixel mapping and my problem has gone away... and here was I thinking my camera was dying!
02-18-2011, 06:11 PM   #4
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That would scare me too.

02-18-2011, 08:08 PM   #5
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As said before, those are hot pixels. Here's some reading if you want more info:
The Imaging Resource Hot Pixels Article
Hot Pixel Facts
Hot Pixels
camera hot pixels - Google

Pixel mapping is one option, and as you mentioned, it got rid of your problem. However, another thing to note is that if you shoot RAW, most decent RAW converters (such as LR) will automatically take care of and map out most hot pixels for you as well.

Last edited by pop4; 02-18-2011 at 08:18 PM.
02-18-2011, 11:04 PM   #6
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QuoteOriginally posted by Stiv Quote
Thanks GregK8!

It's a K7. I've just run pixel mapping and my problem has gone away... and here was I thinking my camera was dying!
It IS. Send it to me and I'll give it a proper burial (in a couple years).

02-19-2011, 02:52 AM   #7
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QuoteOriginally posted by pop4 Quote
Pixel mapping is one option, and as you mentioned, it got rid of your problem. However, another thing to note is that if you shoot RAW, most decent RAW converters (such as LR) will automatically take care of and map out most hot pixels for you as well.
I didn't know that, thanks for the tip
02-19-2011, 02:55 AM   #8
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QuoteOriginally posted by JeffJS Quote
It IS. Send it to me and I'll give it a proper burial (in a couple years).
Umm, I realise you're joking... BUT are hot pixels a sign of a slow and impending death?

02-19-2011, 03:03 AM   #9
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QuoteOriginally posted by Stiv Quote
Umm, I realise you're joking... BUT are hot pixels a sign of a slow and impending death?
I'm glad you got it, because I was. No I don't think the camera is dying. My K7 had 6 or 7 hot pixels right out of the brand new box. Ran the mapping routine, never saw another one. That camera is now on its second owner and he's taking some pretty great photos with it. When you have a big band of them or a large cluster of hot pixels, then worry about it. Keep in mind that they could also be noise. If you're taking 30 minute exposures of the night sky for instance, you may see a few green spots. Still nothing to worry about, clone them out and move on.


Last edited by JeffJS; 02-19-2011 at 03:26 AM.
02-19-2011, 03:53 AM   #10
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QuoteOriginally posted by Stiv Quote
Umm, I realise you're joking... BUT are hot pixels a sign of a slow and impending death?
As it is said before, it is not.

Your camera sensor has 15.000.000 pixels.
Even if 1% were broken and randomly distributed over the sensor (150.000 broken pixels that is), you would not be able to notice them.

So, don't worry, map them out.

One more thing: what firmware revision is your camera on?
Early K-7 firmware revisions were having problems with the sensor and generated "stuck" pixels, green banding and the like.
If you are not, you may want to install the latest K-7 firmware revision.

- Bert
02-19-2011, 04:07 PM   #11
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The camera's on firmware 1.10, fairly sure it's the latest.

I very rarely take these long exposure night time shots so it's probably why I've never noticed these hot pixels before. I've had the camera almost a year now and never touched pixel mapping or known what it does. I read the manual from cover to cover when I bought the camera but some things just don't sink in until you need them
02-19-2011, 07:57 PM   #12
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QuoteOriginally posted by Stiv Quote
The camera's on firmware 1.10, fairly sure it's the latest.
Firmware 1.11 is out: Latest K-7 Firmware Update : Software Downloads : PENTAX
The only publicised changed is the camera is now "Compatible with SDXC memory card," but Pentax being Pentax might've made a few hidden tweaks here and there (or not). Who knows?
02-19-2011, 11:23 PM   #13
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QuoteOriginally posted by pop4 Quote
Firmware 1.11 is out: Latest K-7 Firmware Update : Software Downloads : PENTAX
The only publicised changed is the camera is now "Compatible with SDXC memory card," but Pentax being Pentax might've made a few hidden tweaks here and there (or not). Who knows?
Thanks for the heads up!
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