Logctool

Introduction

Logctool a set of utilities for processing logc encoded images. Test and verification data, including a step chart and color checker classic and digitalsg chart, can be generated for color space evaluation and testing.

Change log:

Date	Description
2025-08-29	Added digitalsg output type
2025-08-27	Fixed bg color issue, now in log
2025-08-27	Added new output type digitalsg

Examples of stepchart, classig and digitalsg output types.

Usage

Print logctool help message with flag --help.

logctool -- a set of utilities for processing logc encoded images

Usage: logctool [options] filename...

General flags:
    --help                           Print help message
    -v                               Verbose status messages
    --transforms                     List all transforms
    --ei EI                          LogC exposure index
    --dataformat DATAFORMAT          LogC format. Options: float (default), uint8, uint10, uint16, uint32
    --transform TRANSFORM            LUT transform
Output flags:
    --outputtype OUTTYPE             Output type. Options: stepchart (default), classic, digitalsg
    --outputfilename OUTFILENAME     Output filename of log steps
    --outputwidth WIDTH              Output width of log steps
    --outputheight HEIGHT            Output height of log steps
    --outputlinear                   Output linear steps
    --outputnolabels                 Output no labels
    --outputfalsecolorcubefile FILE  Optional output false color cube (lut) file
    --outputstopscubefile FILE       Optional output stops cube (lut) file

Generate LogC stepchart in OpenEXR float

./logctool
-v
--outputwidth 2048
--outputheight 1024
--dataformat float
--outputtype stepchart
--outpitfilename /Volumes/Build/github/test/logctool_LogC3.exr

Generate LogC colorchecker in DPX 10-bit

./logctool
-v
--outputwidth 2048
--outputheight 1024
--dataformat uin10
--outputtype colorchecker
--outputfilename /Volumes/Build/github/test/logctool_LogC3.exr

Generate Conversion LUTs in Davinci Resolve

./logctool
-v
--outputwidth 2048
--outputheight 1024
--dataformat float
--outputfilename /Volumes/Build/github/test/logctool_LogC3.exr
--outputstopscubefile /Volumes/Build/github/test/logctool_LogC3_out.cube

Download LogC charts

LogC charts are available EXR float and DPX 10-bit precision, EI 800.

LogC	LUT	Output type	Download
LogC3	LogC3	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	Linear	Stepchart	DCI 2K EXR 4K EXR
LogC3	CanonLog	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog2	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog3	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	Cineon	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	Rec709	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog1	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog2	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog3	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	sRGB	Stepchart	DCI 2K EXR DPX 4K EXR DPX
LogC3	LogC3	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	Linear	Colorchecker	DCI 2K EXR 4K EXR
LogC3	CanonLog	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog2	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog3	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	Cineon	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	Rec709	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog1	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog2	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog3	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	sRGB	Colorchecker	DCI 2K EXR DPX 4K EXR DPX
LogC3	LogC3	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	Linear	Digital SG	DCI 2K EXR 4K EXR
LogC3	CanonLog	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog2	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	CanonLog3	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	Cineon	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	Rec709	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog1	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog2	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	SonySLog3	Digital SG	DCI 2K EXR DPX 4K EXR DPX
LogC3	sRGB	Digital SG	DCI 2K EXR DPX 4K EXR DPX

Building

The logctool app can be built both from commandline or using optional Xcode -GXcode.

mkdir build
cd build
cmake .. -DCMAKE_MODULE_PATH=<path>/brawtool/modules -DCMAKE_PREFIX_PATH=<path> -GXcode
cmake --build . --config Release -j 8

Example using 3rdparty on arm64 with Xcode

mkdir build
cd build
cmake ..
cmake .. -DCMAKE_PREFIX_PATH=<path>/3rdparty/build/macosx/arm64.debug -GXcode

Download

Logcotol is included as part of pipeline tools. You can download it from the releases page:

• https://github.com/mikaelsundell/pipeline/releases

Dependencies

Project	Description
OpenImageIO	OpenImageIO project @ Github
OpenColorIO	OpenColorIO project @ Github
OpenEXR	OpenEXR project @ Github
3rdparty	3rdparty project containing all dependencies @ Github

Limitations

Cube LUTs are limited in their precision therefore does not handle the toe of the curve very well.

Project

• GitHub page
  https://github.com/mikaelsundell/logctool

• Issues
  https://github.com/mikaelsundell/logctool/issues

Related

• Color space conversion
  https://github.com/mikaelsundell/colortool

Resources

• ALEXA Log C Curve
  https://github.com/mikaelsundell/utilities/blob/master/whitepapers/arri/11-06-30_Alexa_LogC_Curve.pdf

• XRite Colorchecker Classic
  https://xritephoto.com/documents/literature/en/ColorData-1p_EN.pdf

• XRite Colorchecker Digital SG
  https://my-classic.xrite.com/documents/apps/public/digital_colorchecker_sg_l_a_b.txt

Copyright

• Arri LogC
  Copyright © 2023 ARRI AG. All rights reserved.

• X-Rite ColorChecker
  Copyright © 2009, X-Rite Incorporated. All rights reserved.

• Roboto font
  https://fonts.google.com/specimen/Roboto
  Designed by Christian Robertson