ARRI LogC4 ACES IDT

for Davinci Resolve, Baselight & OCIO

I have been testing ARRI LogC4 since the release of the new ARRI Alexa 35 camera. In order to work with the LogC4 footage in ACES, an additional IDT profile is required to interpret LogC4 into ACES scene linear color space(AP0). 

The LogC4 IDT profile I created is based on the ARRI LogC4 Specification document. You can find it from ARRI's website.

30/05/2023 Update: I created a new repository containing a full OCIO color configuration for ACES 1.2, along with two new Input Device Transforms (IDTs) for ARRI LogC4 and DJI D-Log. It is ready for use in the DCC applications without any further modifications needed.

06/09/2022 Update: Baselight released version 5.3.17. It updated to ARRI Image SDK 7.0.1. This adds support for:

• support for ALEXA 35 cameras

• additional metadata in ARRI MXF media (ARRIRAW and Apple ProRes)

• from ALEXA 35

• support for HDE-compressed ARRIRAW MXF media

• the "ARRI: LogC4 / ARRI Wide Gamut 4" colour space [bug 59994]

06/06/2022 Update: Blackmagic adds support for the ARRI ALEXA 35 camera in the DaVinci Resolve 18 Beta 6 update. Resolve is now capable to decode the Alexa 35 raw files natively and it also ships with the ARRI LogC4 color profile for ACES. 

If you are on Resolve 17 or not going to update to Resolve 18 Beta, you can still follow the installation guide below to use the LogC4 DCTL I created.

06/05/2022 Update: ARRI recently released some ALEXA 35 Camera sample footage from ALEXA 35 Short film series "Encounters". You can download the sample footage from ARRI's FTP server.

Server: ftp2.arri.de

User:  ALEXA

Password: samplefootage

ARRI ALEXA 35 Sample Footage Technical Information: Download Here

I tried to open ALEXA 35 RAW files in Davinci Resolve 17 and Baselight Look 5.3.16806, but none of them have implemented the latest ARRI SDK to support the ALEXA 35 RAW yet.

The workaround is using ARRI Reference Tool to convert the ALEXA 35 RAW files into ProRes4444XQ, so we can load the ProRes into Resolve, Baselight, or other DCC applications. ARRI Reference Tool 1.0.0.0 Player replaces the old ARRIRAW Converter, the ARRI Meta Extract as well as the ARRI Color Tool. Here you can download a player-only version of the new tool from ARRI's website. The full version of ART will be available soon. 

Here is the step to step setting in ARRI Reference Tool:

The ProRes 4444 files exported from ARRI Reference Tool successfully show up in Davinci Resolve. However, the version of Baselight I use has issues reading ProRes wrapped in the MXF container.

Instead of re-rendering the MXF ProRes file, the quickest and easiest way is rewrapping it into a MOV file. You can use a video converter software like Shutter Encoder or FFmpeg to rewrap MXF.

I also made a shell script (download here) for wrapping only if you already have FFmpeg installed on your workstation. Just copy and paste the script to the same folder that has the ProRes MXF files. Execute the script. It will create a "_rewrapped_mov" subfolder with the PorRes mov files in it.

Davinci Resolve

• Navigate to the "ACES Transforms" folder in Resolve's main application support folder.

  • MacOS: "~/Library/Application Support/Blackmagic Design/DaVinci Resolve/ACES Transforms" 

  • Windows: "%AppData%\Blackmagic Design\DaVinci Resolve\Support\ACES Transforms"

  • Linux: "~/.local/share/DaVinciResolve/ACES Transforms"

• Place Arri_LogC4.dctl in the IDT subfolder.

• Start Resolve.

• At start up, Resolve loads all the ACES DCTLs inside the "ACES Transforms/IDT" and "ACES Transforms/ODT" folders.

• Arri LogC4 is now available as the ACES Input Transform in the project color management setting.

• Arri LogC4 is also available in the drop-down menu if you prefer a node tree based ACES workflow.

Baselight

• Navigate to the "colourspaces" folder for colour space transform files.

  • MacOS: "~/Library/Application Support/FilmLight/etc/colourspaces"

  • Linux: "/usr/fl/etc/colourspaces"

• Place ARRI_LogC4_WG4_full.flspace in the "colourspaces" folder.

• Start Baselight.

• ARRI: LogC4 / Wide Gamut4 is available for Colour Space Input.

OpenColorIO

Please use the full ACES 1.2 OCIO color configuration provided at the beginning of this blog instead.

• This config only contains the code for ARRI LogC4. If you don't have a full ACES OCIO config, you can download the latest ACES 1.2 OpenColorIO configuration files

• Copy the code from Arri_LogC4-config.ocio into the full ACES config.ocio file.

• Copy V4_LogC_800_to_linear.spi1d into the "luts" folder.

• Load the modified OCIO config in DCC applications.

• Input - ARRI - V4 LogC (EI800) - Wide Gamut should be available in OCIO.