ACES
The first time I heard the word ACES was when my colorist Yugendran , with lot of joy and glean in his eyes , told me that , we are going to grade my film with the ACES workflow.
Yugendran’s enthusiasm was infectious. I was very curious about
ACES ?
It got very technical , but I was trying to understand in simple terms.
What is ACES ?
ACESisAcademyColorEncodingSystem .
ACES is a free , open , device-independent color management and image interchange system that can be applied to almost any current or future workflow.
It was developed by hundreds of the industry’s top scientists , engineers and cinematographers , working together under the auspices of the Academy of Motion Picture Arts and Sciences . ( host of OSCARS ).
ACES 1.0 is the first production-ready release of the system.
Some of the characteristics of ACES are :
- Image container is OpenEXR , with support to many channels
- Color space greater than the gamut of human eye
- 16 bit floating point color depth
- Ability to hold more than 25 stops of dynamic range.
See the color gamut picture and the color space of ACES compared to Rec.709 or DCI -P3 or Rec.2020. Its much greater than even the human eye’s gamut.
Why ACES ?
ACES preserves the full information of the capture device , all along, the workflow. It can preserve the full range of highlights , shadows and colors captured on set for use , throughout the post-production and final mastering.
ACES simplifies the matching of images from different capture devices. Grading and matching images from different cameras and from CG or VFX becomes significantly easier. It works as a “universal container” for footage coming from all kinds of cameras, and it can export the finished project to any color space – including those that don’t exist yet . Thats why , its future proof. .
Because of ACES , there won’t be any gamma curve problem with easy access to highlights and deep shadows and beautiful colors.
Same grade can be easily exported to different color spaces , without the need for any special tranforms ; like the existing :
Rec.709 ( HDTelevision ) or P3 ( Digital movie projection)
And
Rec.2020 ( Ultra HD ) or the futuristic Rec.2100 ( HDR display ).
Key Acronyms in ACES Workflow :
In current workflow, the following disadvantages are there :
- Color space is fixed and dependent on current technology
- Encoding is irreversible
- Dynamic range is limited by current display technology
In ACES workflow , ACES files are , basically 16 bit floating point EXRs. OpenEXR file format. Effectively , much bigger colorspace. Bigger than even the human eye can see.
In ACES , the following is a typical workflow :
IDT – LMT – RRT – ODT
IDT –InputDeviceTransform :
Handles transforming imagery captured from whatever camera , into the ACES color space.
LMT–LookModificationTransform :
Once the images are in the ACES colorspace , LMT provides a way to customize a starting point for color correction.
RRT–ReferenceRenderTransform :
In RRT , the images are rendered , but are not optimized for any one output format.
When we try to convert from one file format to another , somehow the colors change. RRT is supremely important to avoid that and make sure the color is consistent.
ODT –OutputDisplayTransform :
Maps the high dynamic range output of the RRT to display referred values for specific color spaces and specific display devices. Each target type requires its own ODT. In order to view ACES images on a broadcast monitor for example, they must first go through the RRT and then the Rec.709 ODT.
