File- and clip-based workflows
Managing near-set work can be an exacting task, encompassing verification, backup, sound sync, color correction, creation of dailies, archival, and many other critical production functions. Fortunately, the production of dailies from ARRI cameras is no more complicated in an ACES workflow than it would be in a traditional ARRI workflow. These pages will limit themselves to a discussion of dailies for delivery to editorial (or other distribution as per the needs of the production).

File-based ACES dailies workflows
ACES can be used in file-based workflows with ARRIRAW files arriving from the set, accompanied by any on-set color correction information (note that ARRI Look Files are not supported for use in ACES workflows). The illustration below shows a Codex Vault that processes Capture Drive cartridges arriving from the set, producing ARRIRAW files (.ari files). These .ari files would be converted to ACES by a near-set system (here, a Colorfront OSD system), the on-set color correction information — probably conveyed as an ASC CDL file — would be applied, and the result would be combined first with any show look, then with the standard ACES output transform. In this manner, the OSD system can create dailies for Editorial with the look and any on-set color corrections "baked in".

The OSD system also creates ACES images packaged in OpenEXR files for Visual Effects. These files are accompanied by "sidecar" files carrying any show look or on-set color correction, so that Visual Effects can preview their composites using the same transforms used by on-set or near-set creative staff.

Camera original ARRIRAW, ProRes and DNxHD
These should be cataloged and archived as would be done for a non-ACES show. Just as ARRIRAW processing has improved through the years, so similarly may the process of converting camera original content into ACES imagery and metadata; careful saving of the original files or clips can allow improved ACES processing in the future.

And if for any reason the production reverts to a more traditional ARRI workflow, it is the saved camera originals that will make that possible.

ACES container files (constrained OpenEXR)
ACES container files should be the primary deliverable for VFX work. An ACES container file is a 16-bit OpenEXR file containing not just the image but also the metadata that distinguishes an ACES-containing OpenEXR file from some other type of OpenEXR file.

ACES container files contain scene-referred data and should not incorporate any Look file effects.

Note that at the present time the ACES container specification only allows for uncompressed OpenEXR files to hold image data and metadata.

ProRes and DNxHD with "baked-in" color for Editorial
As few editorial departments can process the 16-bit OpenEXR images that will be used in the finishing suite, they will need to be provided with the same type of deliverables that they are accustomed to handling today — with the ACES output transform "baked-in".

If ASC CDL was used on-set or near-set on ACESproxy data as part of creative direction, then the effects of the ASC CDL should also be "baked-in" to the delivered dailies. Note that the ASC CDL is intended to work on ACESproxy or ACEScc data, not ACES data, so ACES dailies systems will briefly transform ACES data into ACESproxy or ACEScc, apply the CDL, and transform the result back to ACES.

It is also worth noting that much pain can be avoided at the end of the production if editorial monitors are calibrated according to the same standards used in visual effects and in digital finishing. By default, ARRI tools assume images they produce will be shown on monitors calibrated for Rec. 709 primaries, a Rec. 709 [D65] white point, and a 2.4 gamma response.

ACES does not mandate a particular workflow, but there is a fairly common ACES-based workflow that is flexible enough to meet most production needs. In this workflow, there are four points at which the color values in the captured scene can be changed for creative or for technical reasons: in a show look; in an on-set grade; in a VFX pre-grade; and in the final DI grade. Again, this is not a formal recommendation from the ACES development team, and even when adopted, each step is optional (though only live broadcast is likely to omit the final DI grade). If the workflow sounds familiar, it is because this type of workflow was established for high-end VFX-heavy productions long before ACES was developed.

Looks
Looks are color changes that are applied uniformly across the captured frame, and commonly are applied to many if not all shots in a production. An example look might be one emulating a particular film stock as developed and printed by a particular lab. Looks are typically developed during pre-production by the cinematographer and DIT, with input from other creative staff -- for example, the final DI colorist is often involved in look development.

Technically speaking, looks are applied to data in the linear ACES color space. For looks analytically derived from physical measurements (as would be the case for the print film emulation mentioned above) this causes no difficulty, but a linear space is not particularly colorist-friendly. So looks developed interactively by colorists are often developed in a colorist-friendly color space like ACEScc, and wrapped transparently in ACES-to-ACEScc and ACEScc-to-ACES transformations.

On-set grades
On-set grading is, typically, the application of ASC CDL operations — slope, offset, power and saturation changes — uniformly across the frame to log-encoded ACESproxy data either on-set during the composition of a shot, or shortly after the shot is captured in near-set dailies production. (In this sense, on-set grading is something of a misnomer; it happens as much near-set as on-set.) On-set grades are applied before any look is applied.

VFX pre-grades
Pre-grades are for shot-specific overall changes, typically to deal with uncompensated changes in illuminant over long periods of time. More detail on pre-grading is available in the post-production section, though it is worth noting here that the artists using the pre-graded plates should be provided with the on-set grades as well.

DI grade
The final DI grade is the last opportunity for creative change to the look of the image prior to distribution. More detail on the final DI grade is available in the post-production section, though it is worth noting here that the final DI colorist should be provided with the on-set grade, where it may be used as a starting-point grade, or at least as a historical reference.

ARRI camera output is metadata-rich. When converting ARRI camera output to ACES there are several options for preserving metadata.

ARRI ALEXA cameras
The ALEXA can produce three types of output: ARRIRAW files (or from the ALEXA Mini, ARRIRAW clips wrapped in MXF), ProRes or DNxHD clips, and/or an HD-SDI video signal.

For ARRIRAW-based workflows, the maximum amount of metadata is carried over to the ACES container file when ARRI’s two ARRIRAW conversion programs are used — either the ARRIRAW Converter (ARC) application, or the ARC_CMD command-line tool. These tools fill in from the ARRIRAW file all the required metadata to make the OpenEXR file a compliant ACES container, and embed much more optional ACES and ARRI-specific metadata as well. For details on what metadata is embedded, see the ARRI metadata documentation. For details on how to use the ARRIRAW Converter application, see the Tools section below.

Alternatively, for Codex-based ARRIRAW workflows, ACES-containing OpenEXR files can be generated from the downloaded Capture Drive at the same time as the ARRIRAW files themselves. The Tools tab of this section shows how to use the Codex Vault UI to generate OpenEXR files as well as ARRIRAW files. (The ARRIRAW files should always be produced and saved even in an ACES-based workflow, as they offer the highest-quality archiving of the captured imagery.)

Log C HD-SDI output can be captured and later converted to ACES OpenEXR files as desired, using a third-party tool such as Blackmagic Design’s Resolve or Colorfront’s OSD. ACESproxy HD-SDI output can not be converted to ACES OpenEXR files, however, nor can Rec. 709 HD-SDI output.

ARRI AMIRA camera
For the AMIRA, ProRes Log C or MXF/ARRIRAW clips can be brought into ACES. For on-set or near-set dailies creation, Log C clips can be converted to ProRes Rec709 or DNxHD Rec709 clips using tools such as those described above.

ARRIRAW Converter
ARRIRAW files are the highest-quality path to ACES imagery when capturing a scene with ARRI cameras. The reference conversion tool is ARRI’s freely-downloadable ARRIRAW converter. (Users not already having the ARRIRAW Converter can download it here.) Other portions of ARRI’s website describe its operation, but there are four key settings in the Render Settings "Format & Color Space" tab that must be correctly set to producing ACES files.

• "OpenEXR" should be selected in the pull-down "File Format" menu
• "Scene Lin" should be selected in the pull-down "Encoding" menu
• "Uncompressed" should be selected in the pull-down "Compression" menu
• "SceneLin. - ACES" should be selected in the pull-down "Color Space" menu

A Render Settings panel correctly configured for producing OpenEXR is shown below.