In Camera DNG Color Correction?

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Offline reyalp

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Re: In Camera DNG Color Correction?
« Reply #10 on: 03 / July / 2012, 15:50:52 »
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http://forums.dpreview.com/forums/read.asp?forum=1010&message=39515894

Is all that is mentioned here really necessary?
Those are just settings one person chose to use. Not necessary, and not applicable to all cameras. Read the manual, choose your settings accordingly.
Quote
"The new dev trunk supports a newer version of DNG that does not need the bad pixel file if you get stuck on that step." 
I was one having problems so what version has "DNG that does not need the bad pixel file"?
The trunk / unstable build, found here http://mighty-hoernsche.de/trunk/

If you are not able to generate badpixel.bin with your camera, please post a bug report.

Note the trunk avoids needing badpixel by using DNG 1.3. Very few programs support DNG 1.3 badpixel mapping (basically, adobe  programs i think?) so if you open the DNG with other programs, the bad pixels will appear black. In that case, you could just as well use use the stable build with a dummy badpixel file.
Don't forget what the H stands for.

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Offline KenO

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Re: In Camera DNG Color Correction?
« Reply #11 on: 06 / July / 2012, 10:37:03 »
Hi reyalp,

Thanks for your detailed explanation!  Especially "Note the trunk avoids needing badpixel by using DNG 1.3. Very few programs support DNG 1.3 badpixel mapping (basically, adobe  programs i think?) so if you open the DNG with other programs, the bad pixels will appear black. In that case, you could just as well use use the stable build with a dummy badpixel file."

"Those are just settings one person chose to use. Not necessary, and not applicable to all cameras. Read the manual, choose your settings accordingly."

I have read the manual but as a beginner am would like to find out what options others are using and prefer to not use badpixel removal because read Quote from senior developer ewavr - ‘You can compare bad pixel removal quality in both modes, IMO, 'RAWConv' mode is preferred, because CHDK interpolation is very unsophisticated’.Quote
http://chdk.wikia.com/wiki/CHDK_User_Manual

If there have been recent improvements I could be very interested.

Thanks again for your help!

Ken

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Offline KenO

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Re: In Camera DNG Color Correction?
« Reply #12 on: 06 / July / 2012, 13:56:52 »
Hi reyalp,

Am confused by from reading the CHDK manual Bad pixel removal section "Use this option to remove defective pixels directly while taking an image; this affects also the JPG image, not only the RAW image. This function removes bad pixels ("hot" / "defective" pixels) which are not known by the Canon firmware, i.e. pixels that became defective during the camera lifetime.

Once you have generated a list with all the "bad" pixels for your camera, CHDK can remove them automatically with the [Average] or [RAWConv] option selected, CHDK looks for the file badpixel in the /CHDK folder; this is a plain text file with x/y coordinates of the bad pixels in the raw image.

    with the [Average] setting CHDK calculates the color for the bad pixel based on its four neighbour pixels with a simple average calculation; bad neighbour pixels will be ignored in this calculation.

    the [RawConv] setting means: let an external raw converter software remove the bad pixels later in the workflow. With this setting CHDK just sets the bad pixel to the value 0 (zero), without any other calculation or modification. Most RAW-capable apps will detect this and apply their own algorithms.

To create this badpixel file you need to capture a "dark frame" by shooting an image with the lens completely capped. For shutter speeds longer than 1 to 10 seconds, it's wise to keep a collection of dark-frames on hand for each exposure length that you will be using in the future, as more warm and hot-pixels appear with extended shutter speeds.

To create a list of the bad / defective pixels you can use the show_bad tool from here > http://ewavr.nm.ru/chdk/show_bad.zip (direct download).

    → Read more about this program & how to use it here: Hot/bad pixel removal " http://chdk.wikia.com/wiki/CHDK_User_Manual

Tried the link for show_bad tool but only got 404 error message.

Then did search and found "Talk:Badpixel removal badpixel vs badpixelcopy4.exe" http://chdk.wikia.com/wiki/Talk:Badpixel_removal but too technical for me.

Hope you or someone using CHDK can give an explanation.

Thanks again for your help!

Ken

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Offline reyalp

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Re: In Camera DNG Color Correction?
« Reply #13 on: 06 / July / 2012, 14:44:25 »
As explained in the manual, there are two different, unrelated badpixel removal systems. One is for DNG, and removes only bad pixels known to the canon firmware. If you use DNG 1.2, then the badpixel.bin file must be generated. If you use DNG 1.3, then CHDK just uses some meta-data in the DNG file to tell DNG programs that pixels with zero value are bad.

The other badpixel system allows you to manually map pixels to be interoplated over. This is totally unrelated to DNG.

You can find a copy of show_bad_b here in the chdk box.net https://www.box.com/chdk#/chdk/1/55270403
Don't forget what the H stands for.


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Offline KenO

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Re: In Camera DNG Color Correction?
« Reply #14 on: 10 / July / 2012, 10:31:29 »
Hi reyalp,

Thanks for your detailed explanation!

Forgot to ask, are you using in camera DNG? 

If yes which one and why?

Thanks again for your help!!!

Ken

 

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