Projects often include a variety of media from different sources, and it can be difficult to know what color management to apply. The transforms in the Autodesk Color Management collection have been designed as building blocks to provide maximum flexibility. With an understanding of the concepts presented in this guide, you can combine these building blocks to solve your color workflow challenges. With that in mind, here is an advanced workflow example.
Suppose that you have a project that was mostly shot on 35mm film, but for various reasons some specific shots used different digital cinema cameras. In addition, there are some rendered 3D CG elements as well as title cards. You need to combine all these images to produce multiple deliverables: DCDM for projection in theaters plus HD video for home Blu-ray.
Choose a Working Color Space
Your first step is to decide on a working color space, unless that decision has already been made for you.
- A scene-linear working space is a good idea, especially for compositing the 3D elements.
- Considering that the deliverables are digital cinema (which uses the P3 primaries for projection) and HD (which uses the Rec. 709 primaries), it makes sense to choose the P3 primaries. They have a larger gamut than Rec. 709, so the DCDM can use all of the colors that are available on a SMPTE reference projector. Furthermore by restricting the working space to this gamut, you reduce the possibility of out-of-gamut colors.
- Many people find the DCI calibration white point too green, and prefer to work with a different creative white point such as D60.
So, a suitable choice for a working space is a scene-linear encoding using the P3 primaries and a white point of D60.
Convert the Inputs
Next, you need to convert all the inputs to this working space:
- The film scans are most likely DPX files using ADX or another Cineon-like encoding. You can use one of the transforms in the film/ directory to convert these to scene-linear ACES on import (see Color Managing Images from Scanned Film for additional considerations). Looking at the transforms available in the primaries/ directory, there is no direct way to convert from ACES to the P3 primaries. However, it is possible using two steps: by applying ACES_to_CIE-XYZ followed by CIE-XYZ_to_P3-D60. You can export the whole chain of transforms as a single .ctf file for convenience when importing many shots.
- Digital cinema cameras all use different proprietary encodings. Depending on the camera make, model, and lighting settings, use the appropriate transform from the camera/ directory to convert the images to ACES (see Color Managing Digital Cinema Camera Footage). As with the film footage, you can then convert the images to the P3 primaries by applying ACES_to_CIE-XYZ followed by CIE-XYZ_to_P3-D60 from the primaries/ directory.
- The rendered 3D CG elements are most likely scene-linear images already, but are probably using the sRGB primaries (which are the same as the Rec. 709 primaries). You can convert these images to your working space by applying Rec-709-sRGB_to_CIE-XYZ followed by CIE-XYZ_to_P3-D60 from the primaries/ directory (see Color Managing Rendered 3D CG Images).
- Suppose that the title cards are sRGB images. To convert them to scene-linear, you need to apply an inverse tone map. One way to do this is to apply inversePhotoMap_gamma_2.4 from the tone-map/ directory (see Color Managing Video Footage), and then convert the primaries in the same way as for the 3D elements using Rec-709-sRGB_to_CIE-XYZ followed by CIE-XYZ_to_P3-D60 from the primaries/ directory. However because you will be using the ACES RRT tone map for output (more about that coming up), use the sRGB_to_ACES transform followed by ACES_to_CIE-XYZ and CIE-XYZ_to_P3-D60 — this ensures that the original sRGB values are unchanged by the matching combination of inverse tone map for input and tone map for both display and output.
Set Up the View Transform
Now you need to set up your view transform to display these images as you work. Since the working space is scene-referred, you need to use a tone map to convert the images to output-referred values, and of course you should use the same tone map as the final deliverables. For the purpose of this example, suppose that you decide to use the ACES RRT.
To use any of the transforms in the RRT+ODT/ directory, you must first convert to ACES. You can do this using P3-D60_to_CIE-XYZ followed by CIE-XYZ_to_ACES from the primaries/ directory. Finally, you can apply ACES_to_current-monitor from the RRT+ODT/ directory. Chromatic adaptation is built into these transforms to map the D60 white point of the working space to the monitor's white point. Export this chain of transforms as a single .ctf file and set it as your viewing transform.
In addition, you may want to preview on a projector calibrated to the DCI white point. You can first convert to ACES using P3-D60_to_CIE-XYZ followed by CIE-XYZ_to_ACES from the primaries/ directory as above, and then use ACES_to_P3-DCI from the RRT+ODT/ directory. Although the calibration white is DCI, the creative white is D60, so chromatic adaptation is neither necessary nor built-in (see White Point Conversion).
See Color Managing Images for Display for more information.
Color Managing the Output
Finally, you need to apply the correct transforms for your deliverables. As for the display, you need to use a tone map to convert from scene-referred to output-referred.
Once again, you can convert from the working space to ACES using P3-D60_to_CIE-XYZ followed by CIE-XYZ_to_ACES from the primaries/ directory. After that:
- For the DCDM, apply ACES_to_DCI-60 from the RRT+ODT/ directory.
- For HD video, apply ACES_to_HD-video from the same directory.
See Color Managing Images for Output for more information.