Creating Badpixel.bin

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Creating Badpixel.bin
« on: 06 / December / 2015, 22:41:23 »
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Hi, I am new to CHDK and need help. I hope this is the right place to post this, if not please advise or transfe it to the proper place.

I am using CHDK 1.3.0-4296 on an IR converted SD890is to shoot DNG version 1.1 files.

My problem is:
Using the in camera "Create Badpixel.bin" results in a bad pixel count = 0 and the new Badpixel.bin is empty.
Using show_bad_b.exe with a IMG_xxxx.crw on my PC also generates an empty Badpixel.bin.

I know the camera has a lot of bad pixels from the 2 JPG files generated when using in camera "Create Badpixel.bin". Furthermore all P&S have them by thousands.

Can someone help me so I can get everything properly setup to get best quality DNGs possible.

Pierre

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Offline reyalp

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Re: Creating Badpixel.bin
« Reply #1 on: 06 / December / 2015, 23:29:32 »
Hi, I am new to CHDK and need help. I hope this is the right place to post this, if not please advise or transfe it to the proper place.

I am using CHDK 1.3.0-4296 on an IR converted SD890is to shoot DNG version 1.1 files.

My problem is:
Using the in camera "Create Badpixel.bin" results in a bad pixel count = 0 and the new Badpixel.bin is empty.
Using show_bad_b.exe with a IMG_xxxx.crw on my PC also generates an empty Badpixel.bin.

I know the camera has a lot of bad pixels from the 2 JPG files generated when using in camera "Create Badpixel.bin". Furthermore all P&S have them by thousands.

Can someone help me so I can get everything properly setup to get best quality DNGs possible.
Can you upload a DNG version 1.3 file from this camera somewhere, using the same Canon firmware settings as you've used when you try to create badpixel.bin? The forum doesn't allow attachments that large, but you can use dropbox, google drive etc.

The bad pixel code looks for 0 values, which normally indicates pixels the canon firmware already knows are bad. It won't do anything about hot pixels. It's possible that this camera doesn't use 0, or that there is something camera setting which is preventing the badpixel code from working properly.
Don't forget what the H stands for.

Re: Creating Badpixel.bin
« Reply #2 on: 07 / December / 2015, 11:23:40 »
Thank you reyalp for your prompt reply.

I added both version of DNG files in case it is needed there

https://www.dropbox.com/s/xkxcswz3kzdls3k/IMG_0049_1_1.DNG?dl=0

https://www.dropbox.com/s/jkzdsnsp129fuis/IMG_0050_1_3.DNG?dl=0

I hope these will help to solve the problem and thank you so much for taking the time to help me.

Pierre

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Offline reyalp

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Re: Creating Badpixel.bin
« Reply #3 on: 07 / December / 2015, 16:29:05 »
Thank you reyalp for your prompt reply.

I added both version of DNG files in case it is needed there
Thanks. Looking at the 1.3 DNG, there are in fact no 0 valued pixels, so from a CHDK POV, everything appears to be working correctly. This doesn't mean your sensor has no bad pixels (unlikely, as you say) but the kind of pixel badpixel.bin would deal with is not present in this image, so the 0 bad pixels is correct.

There are ~350 pixels with values below the nominal black level of 127, but it doesn't look to me like the camera is using a different value to mark "bad". There are none with a value less than 81, and the number increases with higher values, which is a pattern seen on other cameras. I wouldn't expect these to affect image quality much, but you could patch them with a manual badpixel list if you wanted.

I notice the exif says this was shot at ISO 400. It's possible that this camera will exhibit different behavior at other ISO values, for example at high ISO the cameras own processing might be doing something with the bad pixels. I would try at the lowest ISO (50 according to the specs, which is a bit unusual)

Examining the image in raw therapee, I only see a relatively small number of hot pixels, which CHDK badpixel.bin would not address anyway. Again, these could be addressed with manual badpixel removal.

Converting with Adobe's DNG validate gives extremely ugly results (speckles of saturated green and purple) but I suspect this is due to the IR filter removal. You can find some previous discussion of DNG with IR modded cameras in this threads
http://chdk.setepontos.com/index.php?topic=11475.0
http://chdk.setepontos.com/index.php?topic=10520.0

I seem to remember there were some more specifically discussing color but I didn't find them.
Don't forget what the H stands for.


Re: Creating Badpixel.bin
« Reply #4 on: 07 / December / 2015, 19:02:51 »
Thank you very much, this was very informative.
I will look at the links you gave.

Thanks again,
Pierre

 

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