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sx10 bad pixels count over 20 thousand - is it normal?

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Offline pi3.14

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sx10 bad pixels count over 20 thousand - is it normal?
« on: 30 / June / 2009, 09:19:30 »
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Hi all,
I just get the chdk for my sx10 1.01b, and I began to shoot in DNG. But before that I ran badpixel.lua, but I noticed the bad pixels count increased each time I ran the script, and at last the number became stable at about 22xxx (don't remember exact number).

The first run of the script only resulted 7xxx; then I tried again with the lens cap on, this time the count increased to over 10 thousands. I become nervous and ran the script for more times and get the results above.

I don't know if the bad pixels count are normal or not - should I return the camera for an exchange. Do anyone here have such results?  :'(

btw, I also own an a630, whose bad pixel count is between 1000 and 2000.

Expecting your input...
« Last Edit: 30 / June / 2009, 09:35:26 by pi3.14 »
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Offline felipegeek

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Re: sx10 bad pixels count over 20 thousand - is it normal?
« Reply #1 on: 01 / July / 2009, 02:37:48 »
Pi,

I had the same experience.  My first run comes in at 6700 then 13400 and it tops out at over 19000.  If I reboot the camera and try again I have similar results.  I am not sure which results to take and not completely clear on what the camera should be pointing at (white card, lens cap on, etc.) when conducting the tests.

I did find when saving as DNG that various pictures, especially darker ones, contained oddly colored pixels scattered all about the image.  I am still very new to this camera and the CHDK firmware so I figure there is plenty for me to screw up yet.

I hope I get to understanding this better soon.

-felipe
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Offline pi3.14

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Re: sx10 bad pixels count over 20 thousand - is it normal?
« Reply #2 on: 01 / July / 2009, 10:03:19 »
Quote from: felipegeek on 01 / July / 2009, 02:37:48
Pi,

I had the same experience. 
...
I hope I get to understanding this better soon.

-felipe
I am a little relieved to see that someone shares my experience. There is so much to learn.
But I cannot get the count number down after reboot,  not even after an new installation of chdk.
Any way, I can mask the bad pixels with chdk. So I should try to live with it.
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Offline nonno

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Re: sx10 bad pixels count over 20 thousand - is it normal?
« Reply #3 on: 01 / July / 2009, 17:54:22 »
as far as i know the script just reads the badpixel values stored in a file in the camera by the manufacturer (that file can also be updated by canon assistance), so your problem is strange. Maybe a CHDK developer can solve it.
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Offline reyalp

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Re: sx10 bad pixels count over 20 thousand - is it normal?
« Reply #4 on: 01 / July / 2009, 20:16:49 »
Quote from: nonno on 01 / July / 2009, 17:54:22
as far as i know the script just reads the badpixel values stored in a file in the camera by the manufacturer (that file can also be updated by canon assistance), so your problem is strange. Maybe a CHDK developer can solve it.
Not exactly. The script counts the pixels that the canon firmware set to 0. How the canon firmware does this is not well understood. Actual black pixels are at CAM_BLACK_LEVEL, which is usually 31 or 127, not zero.

The behavior described suggests that it is more complicated than just a list in the camera flash. It could be something like a temperature sensitive lookup table, or some magic that happens within the image processing side of digic.

Since the CHDK badpixel code ignores pixels that are in the bad pixel list but not zero, it's probably a good idea to use the largest badpixel list.  Badpixel processing is a pretty minor fraction of the DNG saving time.
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