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Old Jul 7, 2008, 12:13 AM   #1
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I noticed a couple of red dots on some recent photos. Is this the beginning of a larger pixel problem? I've cropped the original even more to show the red.

Jim

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Old Jul 7, 2008, 12:13 AM   #2
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Old Jul 7, 2008, 3:38 AM   #3
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They are hot pixels. Run through the sensor cleaning operation on the menu, it will automaticallly check for those pixels and map them out in future.
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Old Jul 7, 2008, 3:38 PM   #4
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Thanks for the tip. I tried it out but still have the spots. I think I will take it to Canon if it gets worse.

Jim
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Old Jul 8, 2008, 3:02 AM   #5
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If the sensor clean didn't map them out I'd take it back now. Shouldn't have to live with that.
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Old Jul 8, 2008, 11:54 PM   #6
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Here's a funny story. I bought the 40D because my 30D gave up at the beginning of a three week Christmas holiday. The new 40D was in for back focusing problems in the spring. Now at the beginning of a five week holiday there is a pixel issue with the 40D! Since there are only two hotspots, I'm going to wait until I go back to work before it goes in.:sad:
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Old Nov 29, 2008, 4:59 PM   #7
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Hello killdeer0007. I guess the exposure time was quite long when taking that picture? Hot pixels are normal in long exposure times, if you don`T want to see those, you just need to switch on "Long exp. noise reduction" under "C.Fn II : Image"
peripatetic, sensor cleaning don`t map out hot pixels.
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Old Nov 30, 2008, 12:13 PM   #8
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Common wisdom is that it does.

I have seen a couple of hot pixels dissapear from my sensor after running through the sensor clean routine.

If you have specific information from a Canon rep or Canon literature that it does not then I would love to know for sure. If on the other hand you are just speculating then...
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Old Dec 1, 2008, 2:33 PM   #9
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Shaking off dust from sensor is what "Sensor cleaning" does. Hot pixels are something else. They appear only with long exposure, usually salready omething like 1/10-1/20 s but they are very well visible when you take photo in total darkness with long exposure (some seconds).
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Old Dec 1, 2008, 4:20 PM   #10
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I know the difference.

If you google the topic you will find out that it is believed that on at least some of the Canon DSLRs there is an undocumented feature of the sensor cleaning routine which tests for and maps out hot and dead pixels, effectively just eliminating them from the readout. All sensors have some hot and dead pixels, they are pre-mapped at the factory but things can go wrong after that too.

I have personally experienced this with my 5D, a couple of red pixels that used to be there were no longer there after running the sensor cleaning routine, which of course in the 5D doesn't actually shake anything, just flips up the mirror so you can get access to the interior for cleaning.

I don't suppose you have any particular reason to believe that I am not a moron, but the thread showed very clearly the OP was talking about those red dots - have you ever met anyone who confuses red dots with dust?

So once again, if you actually KNOW anything different I'd be interested to hear it. If on the other hand you are just repeating what's in the manual then we'll just leave it at that eh?

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