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02-09-2009, 11:40 AM   #1
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Dead pixel/white spot on RAW pictures

Hi,

I started shooting RAW since I got a bigger memory card on my K200D. And yesterday as I was playing around with some RAW pictures I took last week, I saw a white dot.
I wasn't sure what to think at first, so I started looking at some older RAW pic. I had, and well I found quiet few with the same white pixel, on the same spot of course.
Now, I'm shotting RAW in PEF format.
There are few things I just noticed. On the pic. where I shot with small ISO, I don't see the white dot. Only the once I have with ISO 500 and up, I can see it. Where the ISO is 200, the dot doesn't exist. And as well, on the JPEG pic, you don't see the dot as well, so I can't really post any pic. Well..as I'm writing this and looking at the pic. I found another interesting thing. On the original JPEG pic. from the camera you can't see the dot. But now I tried saving a RAW pic. to JPG, and you I can see it. You can not see it as clearly as on the RAW pic. but I will try posting it.

PS:Had to crop it down, hope it helps.

If you guys know, what's up with it, please let me know. The dot, looks like a dead pixel. It's white, and just one.

Thanks

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Last edited by Diasfu; 02-09-2009 at 11:50 AM.
02-09-2009, 02:03 PM   #2
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Try the pixel mapping feature of the camera.
Page 216 of the manual.

- Bert
02-09-2009, 02:15 PM   #3
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I did try it, but didn't make a difference.
Regards
02-10-2009, 08:22 AM   #4
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QuoteOriginally posted by Diasfu Quote
I did try it, but didn't make a difference.
Regards
Try warming up the camera. See if the hot pixel appears with ISO 100, if it happens then try the pixel mapping feature again.
Hope it helps, otherwise, use your waranty.

- Bert

02-10-2009, 08:50 AM   #5
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Well..an update..

Yesterday, tried shooting some pictures with different ISO, and had a look at them. But there was nothing there. I tried as well shooting with the same settings as the pic. with the white pixel were, but nothing. Perfect picture.
Of course I was happy, but surprised as well.

Can anyone explain? Will this happen again? Or what actually happened?
Should I go to the shop with the camera? I only got it last August.

Regards
02-10-2009, 11:28 AM   #6
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QuoteOriginally posted by Diasfu Quote
Well..an update..

Yesterday, tried shooting some pictures with different ISO, and had a look at them. But there was nothing there. I tried as well shooting with the same settings as the pic. with the white pixel were, but nothing. Perfect picture.
Of course I was happy, but surprised as well.

Can anyone explain? Will this happen again? Or what actually happened?
Should I go to the shop with the camera? I only got it last August.

Regards
Your camera most likely is not broken.
You will find hot pixels in almost all CCD sensors. Hot pixels are a well known problem.
Your CCD sensor is an electrical, analogue device. Light (photons) initiate free electrons in each pixel (charge device), which are creating a certain charge (i.e. voltage) in the pixel.
The more photons, the higher the charge. There is more than one reason for electrons to be triggered. Temperature is one, radiation another. Production flaws can result in pixles that react faster than others.
Semi conductors have "burn in" effects as well. This is what will cause electrical circuits to change behaviour and also to fail over time.

Most likely your hot pixel has been detected by the camera and is mapped out.
Also many image processing software packages map out broken pixels.
If your camera cannot deal with it, turn it in, otherwise be happy with it.

- Bert
02-12-2009, 04:22 AM   #7
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Thank you Bymi141.

Nice explanation. I just hope it won't be happening often. It was quiet cold that day. Other than that, I love the camera. Looking to buy a new lens, not sure which one yet..

Anyways, thanks to all!
02-12-2009, 08:07 AM   #8
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You will have hot pixels now and then. This is unavoidable and to some degree just a statistical phenomenon. But in most images you won't see them... That is the good message. I would simple forget about that, as at the end of the day dust on the sensor is much more prominent.

Ben

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