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Correct bad pixel permanently?

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Offline stanelie

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Correct bad pixel permanently?
« on: 08 / July / 2008, 14:09:53 »
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Hi all.

I have successfully used CHDK to correct a dead pixel in my S3.

Is there a way to have this correction permanently burned into my camera's firmware?

Thanks.
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Offline LjL

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Re: Correct bad pixel permanently?
« Reply #1 on: 08 / July / 2008, 14:19:35 »
Not that I (or anyone here, I suspect) know of, and it would be potentially dangerous to change the firmware, anyway.

What's wrong with just loading CHDK on startup?
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Offline stanelie

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Re: Correct bad pixel permanently?
« Reply #2 on: 08 / July / 2008, 14:52:43 »
A few things...

CHDK has to be on the sd card, so, if I replace the card without access to a computer to put it on the card, I have the bad pixel.

Also, to have CHDK load on startup, the memory lock of the sd card has to be on, and it has to be switched back off whenever the card is being accessed by the computer to allow the computer to delete files on the card. I worry about that switch wearing off in the long run. And it's a hassle.

Does that make any sense?
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Offline LjL

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Re: Correct bad pixel permanently?
« Reply #3 on: 08 / July / 2008, 15:56:43 »
Yeah, I'd like to avoid the switch switching myself, given I'm getting the card in and out of the reader all the time currently...

But I don't think you can get what you want in this case - although who knows.

Although you can, as far as I've read, send the camera to Canon for permanent bad pixel mapping (don't know for what price, if any price during warranty period...).
« Last Edit: 08 / July / 2008, 15:59:34 by LjL »
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Offline fe50

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Re: Correct bad pixel permanently?
« Reply #4 on: 08 / July / 2008, 17:24:46 »
Quote from: stanelie on 08 / July / 2008, 14:52:43
...Also, to have CHDK load on startup, the memory lock of the sd card has to be on, and it has to be switched back off whenever the card is being accessed by the computer to allow the computer to delete files on the card. I worry about that switch wearing off in the long run. And it's a hassle.

You can use a card reader that ignores the write protection - it's only a software setting.

If you can't find such a card reader you can easily prepare one by your own, in the forum you'll find some posts with informations & pictures about this "Card reader mod".
( here's another one).

With such a reader you never have to unlock your card - only when you want to work without CHDK !
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Offline DataGhost

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Re: Correct bad pixel permanently?
« Reply #5 on: 09 / July / 2008, 16:29:19 »
It's certainly possible but I have no idea how to do it yet. I noticed that a dark frame RAW (when dark frame subtraction is still busy) contains many more hot pixels than a dark frame RAW with Canon's NR disabled. This implies that the camera does some badpixel mapping regardless of the NR setting. Now, every sensor is different so this setting is likely not in firmware but somewhere in NV memory, overwritable. I just don't know where :) I don't have the simplest of cameras to figure this out, the shooting procedures are quite complex. It should be much easier to figure out the subroutine responsible for badpixel remapping on a simple camera.
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Offline LjL

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Re: Correct bad pixel permanently?
« Reply #6 on: 09 / July / 2008, 16:48:53 »
Are you sure it doesn't just remove pixels that are just way different from their neighbors, on the fly?

Sometimes, when I shoot, I notice that the review image shows quite a bit of noise in the form of warm pixels for a split second - then they go away.
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