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Howto/ manual bad pixel removal

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Offline Adrien Cattelain

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Howto/ manual bad pixel removal
« on: 01 / August / 2018, 22:01:15 »
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Hello Everyone,
I'm new on this forum, and just started using CHDK as I was looking for a way to clear white dots appearing on my good old Powershot G12 recently.
These are stuck pixels, they appear at the exact same spot on each photo

I've skimmed all the Wiki and Forum, and got all the configuration done but I still can't get the badpixel removal function to work.
I've got all these steps done :
* CHDK installed and running on my SD Card
* Got the Badpixel.bin set up but I'm not very familiar with DNG so that's not what I'm looking for.
* generated my badpixel list. The Wiki is not clear at all about this, link is broken and I had to find ewavr's "show_bad" program, then get the correct resolution in the source, compile it and find out which raw file type to use.
* Now my badpixel map is OK, saved in the CHDK folder in my SD Card besides badpixel.bin and also copied as .txt
* in CHDK Raw Settings, Manual badpixel removal is set to Average.

But whenever I take a picture, either in RAW or JPEG, white dots are still visible...
I don't have any Idea what to do next...
do someone have experience with using this function on the G12?

thank you so much!
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Online reyalp

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Re: Howto/ manual bad pixel removal
« Reply #1 on: 02 / August / 2018, 00:30:03 »
My guess would be the badpixel file isn't actually right. If you want to post the file and a CHDK DNG taken with version set 1.3 and badpixel turned off, I can take a look.

The DNG will be too big for the forum, you can put it on a site like dropbox or google drive.

FWIW, you can also use chdkptp to generate the manual badpixel list, see https://app.assembla.com/spaces/chdkptp/wiki/DNG_Processing
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Offline Adrien Cattelain

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Re: Howto/ manual bad pixel removal
« Reply #2 on: 06 / August / 2018, 20:55:15 »
Hi reyalp, thanks for your reply,
I didn't have my camera these last days so I'm a bit late sorry
If you can have a look, i've uploaded my files here :
https://www.dropbox.com/sh/g8ajah0r3oqlo6j/AABQfo4JVlChMbCMZtxSU5Zfa?dl=0

I'll give a try with chdkptp and update my post if I get it working :)
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Offline Adrien Cattelain

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Re: Howto/ manual bad pixel removal
« Reply #3 on: 06 / August / 2018, 22:29:00 »
Hi again;
so I gave a quick try with chdptp and I still see a few white pixels, but most of them did disappear!
the result is a lot better than before!

I'll still play a bit more to get rid of the 2-3 that are annoying but your solution works
Thank you so much

I'll write a short version for whoever is also looking for it :
-> got the binaries here https://app.assembla.com/spaces/chdkptp/documents
-> took a few black shots with different ISO and Aperture time / with CHDK set on DNG v1.3, badpixel correction disabled.
-> copied them in the binaries folder and ran the following (on Linux) :
Code: [Select]
./chdktptp.sh
dngload IMG_0001.DNG
dnglistpixels -min=4095 -out=badpixel.txt -fmt=chdk
    did this for the different pictures to get different badpixel.txt files;
    ->then copied them all together in a single file on the SD Card,
    ->back in the camera; enabled badpixel correction on CHDK

    ... shot new pics and no more white dots!    :D
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    Online reyalp

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    Re: Howto/ manual bad pixel removal
    « Reply #4 on: 06 / August / 2018, 22:56:10 »
    Quote from: Adrien Cattelain on 06 / August / 2018, 22:29:00
    did this for the different pictures to get different badpixel.txt files;
    ->then copied them all together in a single file on the SD Card,
    ->back in the camera; enabled badpixel correction on CHDK
    Glad to hear it worked.

    It would be preferable not to have duplicates in the file. If you haven't already, piping through sort -u should work.

    Also, in the example -min=4095 only catches pixels with the brightest possible value on a 12 bit sensor. You could use a lower value (like 4090 or something like that) to catch pixels that are "hot" but not totally saturated. Just use an image where the real scene is dark. If you want to to be sure, there are some scripts you can use to take pictures with the shutter closed:
    https://chdk.wikia.com/wiki/Lua/Scripts:_Fixed_Exposure_Intervalometer
    https://chdk.wikia.com/wiki/Meteor_Intervalometer_with_Dark_Frame_Management

    You will get more hot pixels with longer exposures, higher ISO and higher sensor temperatures

    You can use the dnghist command in chdkptp to see how many pixels fall in a particular value range.
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