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Badpixel removal

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This page contains information on the CHDK Bad pixel (hot pixel) removal function.   This function is different from the badpixel.bin removal function used with for DNG images in CHDK.

To remove defective pixels in an image in CHDK, there is the Bad pixel removal feature. Once a list containing all the bad pixels for your camera has been generated, CHDK can remove them automatically. The file with the badpixel data is named badpixel (without a filename extension).

badpixel <--> badpixel.bin

Q: Why are there two different files for bad pixel removal—what's the difference?

A: The two bad pixel files have slightly different names and are used for different purposes.

The badpixel file is for bad/hotpixel removal in both JPEGs and RAW/DNG. This function can remove hotpixels that are unknown to the Canon firmware.  Use of this file is enabled by the CHDK RAW menu item "Manual bad pixel removal".

The badpixel.bin file is required for saving DNG version 1.1 images.  It is generated using the Create badpixel.bin menu option in the CHDK RAW menu.  In the RAW images,  pixels identified in this file are only masked (value = 0), so depending on the software used there will be black dots in the image. CHDK will interpolate over these pixels. DNG version 1.3 does not require or use badpixel.bin, many raw processing programs will not fix bad pixels in this format.

Historical technical information is available from the CHDK forum : Save RAW files in DNG format instead of RAW.

Software

In camera

As of build 1039, badpixel.bin may be created in camera in the raw menu, using "Create badpixel.bin".

To use this option, the camera must be in record mode. It automatically takes two pictures, calculates the badpixel data and then it creates the badpixel.bin file. This procedure takes ~20-40 seconds of time. Any existing badpixel.bin will be automatically overwritten if the process is successful.

The process will fail if the the two shots do not result in the same number of bad pixels. Some cameras have multiple bad pixel tables, which depend on exposure, temperature or other factors. In this case, retrying should eventually be successful. Bugs in a particular port may also prevent successful bad pixel generation.

show_bad_b

show_bad_b by ewavr - with this command line tool you can generate the bad pixel list on a Windows PC.

Usage:

show_bad_b.exe <CHDK_RAW_FILE_NAME>

The output file badpixel.bin is created in the current folder and the defective pixel count is reported.

  • Try several RAW files to obtain a stable result (approximate shooting conditions: minimal ISO, exposure time ~1/5s-0,8s).
  • Some cameras have two defective pixel lists, which are switched at exposure time ~1/25s. Use the list with maximum (but stable) defective pixel count, otherwise you may see multiple black points on image in some RAW convertors.
  • Some cameras (IXUS960IS) have three defective pixel lists, which are switched at exposure time ~1/6s and ~1/25s (at lowest ISO). Use the list with maximum (but stable) defective pixel count, otherwise you may see multiple black points on images in some RAW convertors.
  • For DNG RAW shooting place the file here: \CHDK\badpixel.bin

Download: Links section

note show_bad_b.exe only supports certain cameras, you may have to update the source for your sensor resolution and bit depth.

badpixel.lua

Prior to build 1039, a script was used to generated the badpixel.bin file. Support for this script has been removed from all recent versions of CHDK. Instructions referencing this script are probably obsolete.

BadpixelPro (outdated)

Badpixel Pro by Johann Meißner - a GUI tool to manage and generate the badpixel list on a Windows PC or on an Intel Mac.

Note: This tool is outdated and may not work with newer camera ports, there's no support or feedback from the author available !

Usage:

→ just start Badpixel.exe
  • It's quite easy to use this new version so no manual is required.
  • You can create several files (ASCII, binary files and bitmaps) from CR2 and binary Files.
  • The Mac version creates only ASCII files from CR2 RAW files.
  • Try several RAW files to obtain a stable result (approximate shooting conditions: minimal ISO, exposure time ~1/5s-0,8s).
  • Some cameras have two defective pixel lists, which are switched at exposure time ~1/25s. Use the list with maximum (but stable) defective pixel count, otherwise you can see multiple black points on image in some RAW convertors.
  • Some cameras (IXUS960IS) have three defective pixel lists, which are switched at exposure time ~1/6s and ~1/25s (at lowest ISO). Use the list with maximum (but stable) defective pixel count, otherwise you may see multiple black points on images in some RAW convertors.
  • For DNG RAW shooting place the file here: \CHDK\badpixel.bin

Links

  • show_bad_b: Generates the badpixel.bin file - binary format (DOS/Windows command line):
author's site or chdkfiles@google drive
  • show_bad: Generates the badpixel file - text format (DOS/Windows command line):
author's site or chdkfiles@google drive
  • show_bad, show_bad_b modified versions
badpixel - show_bad_b mod
  • BadpixelPro: The badpixel tool for Windows and Intel Mac with a graphic interface.
[chdkfiles@google drive (not working without flash)

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