Badpixel removal

This page contains information on the Bad pixel (hot pixel) removal function 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).

• More information on this feature can be found here:
  • User manual: Bad pixel removal
  • Firmware usage: Hot-pixel removal.

badpixel <--> badpixel.bin

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

A: The badpixel.bin file is only needed for DNG creation—it includes the badpixels from the Canon firmware. In the RAW image these badpixels are only masked (value = 0), so depending on the software used there will be black dots in the image. The file can be generated with the badpixel.lua script, included in the "complete" download package; a dummy file containing only zeros can also be used. DNG support will be enabled by this, but the bad pixels will not be removed (Forum link: [1]).

The file badpixel is for the "standard", usual bad/hotpixel removal (also in JPEGs) - this function also removes hotpixels when they are unknown to the Canon firmware. This file contains the badpixel information already stored in the Canon firmware. Read more in the 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". This option is only available if the DNG supported on the camera.

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

As of build 1039, this script is obsolete. Support for it will be removed in the future.

In the complete download packages there's the script badpixel.lua (located in the folder \CHDK\SCRIPTS\TEST) to generate the badpixel.bin file on-the-fly in the camera.

Just run the script: 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. At the end of the process you can save the file with the SET button.

• The current version of the script can also be downloaded directly from the SVN server: badpixel.lua

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):

direct link from author's site or chdkfiles@google drive

• show_bad: Generates the badpixel file - text format (DOS/Windows command line):

direct link from author's site or chdkfiles@google drive

• BadpixelPro: The badpixel tool for Windows and Intel Mac with a graphic interface.

[chdkfiles@google drive (not working without flash)