Using the ACES CDL Grading Mode

Silverstack XT and Lab have the capability of reproducing ACES workflows.

All ACES versions support different IDTs (Input Device Transforms) and ODTs (Output Device Transforms). Please, make sure that the ACES version used in Silverstack matches the one used during the post production process for maximum color accuracy.

ACES Grading Modes

Silverstack implements this pipeline in the ACES (Academy Color Encoding System) grading modes. You can see the nodes and controls of the “ACES CDL” grading mode in the screenshot below. On every interaction with the color controls of the ACES grading mode (e.g. change of IDT, modify of ASC-CDL) all transforms are baked together automatically and are applied to the image.

Grading controls in the "ACES CDL" grading mode.

Grading controls in the “ACES CDL” grading mode.

Silverstack also offers the “ACES CDL Advanced” grading mode. This grading mode lets you add multiple grading nodes between the IDT and ODT and LMTs for advanced workflows.

The CDL controls behave the same way as in the CDL Grade mode and can also be exported as usual from a saved grade. ACES grades can also be exported as 3D LUTs, including the CDL values, IDT and ODT.

From ACES version 1.3 you can enable the “Reference Gamut Compress” parameter within the IDT node of ACES grading modes. The ACES Reference Gamut Compression achieves better accuracy with extreme color ranges and replaces the LMT “Blue Light Artifact Fix” that was widely used in previous ACES versions.

The metadata fields “ACES Input Transform”, “ACES Input TransformID”, “ACES Output Transform”, “ACES Output TransformID”, “Reference Gamut Compress” and “LMT Nodes” allow inspecting ACES look metadata in the shot library and communicating relevant info in PDF reports.

Look Modification Transforms (LMTs)

You can add a “LMT” node in Silverstack (in the ACES CDL Advanced grading mode) that supports the official, predefined LMT transforms shipping with the respective ACES version as well as custom 3D LUTs.

Note: LMTs are specified by the ACES specification as a transform from and to ACES AP-0 (the linear ACES color space). When using 3D LUTs as a way to exchange “LMTs”, these 3D LUTs are usually intended to be applied in a typical grading working color space such as ACEScct (3D LUTs cannot properly represent transforms to be applied in linear color encoding as they would not be able to provide the necessary fidelity in all brightness levels). So in Silverstack, the “LMT” node is applied in the working color space (for instance ACEScct).

Managing ACES Versions

Silverstack supports multiple versions of ACES, ranging from 0.7.1, 1.0, to the latest ACES version 1.3. For compatibility with the post production workflow please choose the right ACES version, as the transforms can be slightly different in different versions, and newer version usually include more and more recent input (IDT) and output (ODT) transforms, including RRT+ODT transforms for HDR in ACES version 1.1 or higher.

Note: Transforms for ACES version 1.3 can be downloaded from Silverstack v8.2 or higher

In the Silverstack preferences you can manage the available ACES versions and transforms:

Fig. 2: ACES preference panel

ACES preference panel

The dropdown lets you select the ACES version for new looks. Every new look will be initialized with the ACES version selected in the dropdown in the preferences.

That means that every look in the library made with an ACES grading mode has an associated ACES version (you can find that version in the “ACES Mode” column in the Silverstack library). Saving looks with different ACES versions to the library will make it easy to compare the look of different ACES versions effortlessly.

The icon in the status bar will either signalize an available set of transforms (green checkmark) or a set of transforms that can be downloaded from the servers (download icon with downwards arrow).

Click the button “Check for New Versions” at the bottom of the preferences window to see if new ACES versions are available to download from the Pomfort servers.

Available ACES Versions

Different versions of the ACES are available from the application preferences (see also section “Managing ACES Versions”) :

  • v 1.3.0 (Working Color Space: ACEScct and ACEScc)
  • v 1.2.0 (Working Color Space: ACEScct and ACEScc)
  • v 1.1.0 (Working Color Space: ACEScct)
  • v 1.0.3 (Working Color Space: ACEScc and ACEScct)
  • v 1.0.2
  • v 1.0.1
  • v 1.0.0
  • v 0.7.1
  • v 0.7.0
  • v 0.2.0

ACES grades can also be exported as 3D LUTs, including the CDL values, IDT and ODT.

Exporting ACES-based Looks as AMF

Silverstack can export the current look of a clip using “File > Export > Looks from Clips…” to export looks from all selected clips or stored looks in the look library as AMF files (“ACES Metadata Files”, .amf). Currently the export of AMF is limited to the ACES CDL grading mode.

For more information about exporting Looks from the Silverstack Look Library see the article Exporting Looks from Silverstack.

Supported ACES IDT and ODT Transforms

Silverstack offers all officially (in the Academy’s repository) available IDT and ODT transforms, as well as a few custom transforms by Pomfort. Please take a look at the available transforms in Silverstack’s preferences in the “ACES” tab.

ACES landing page

See for an overview of ACES related topics with Pomfort’s products.