Guidelines for Configuring Custom Color Transform Chains Manually

Although Autodesk Color Management provides tools to automatically apply the required transforms to convert between color spaces, there may be special situations where you require more control over the specific transforms to apply. This section describes how you may use the components found in the Autodesk color transform collection as building blocks to assemble customized conversions for specific tasks.

In Creative Finishing products, you have the option of using Custom mode to specify a transform from the collection or another source, or to create a chain of several such transforms. For other applications, you may need to use a text or XML editor to create and edit .ctf files. In either case, see Custom Color Transforms for details.

The question of which transforms to apply depends on the specific situation. These situations can be divided into categories that require similar treatment.

Topics in this section

Color Managing Images on Input
When manually applying custom color transforms to imported images, you should convert them to a connection space and then to your chosen working space. Different types of images require different transforms.
Color Managing Images for Display
Images need to be transformed from the working space so that they appear correctly on your display while you work. If you are manually setting up a chain of transform to do this, you need to define the monitor transform as well as apply a viewing transform. In addition, your monitor should be calibrated periodically.
Color Managing Images for Output
If your working color space does not match the color space of your deliverables, the colors must be transformed for output. When you are manually setting up a custom chain of transforms to accomplish this, there are several transforms that can be used, depending on your working space and the desired output.
Color Managing Images from Scanned Film
Images from scanned film are typically supplied as DPX files with Cineon-style log encodings. However, the Cineon encoding was never fully standardized, and various vendors use slightly different implementations. If you are manually setting up color transforms to import scanned film plates, there are several approaches to choose from.
Color Managing Digital Cinema Camera Footage
When manually specifying a color transform for importing footage from a digital cinema camera, use one of the transforms in the camera/ directory. There are various options for different camera models and lighting conditions (e.g. daylight or tungsten).
Color Managing Video Footage
When manually specifying color transforms for importing video, you can use the transforms in the gamma/ directory to remove the gamma that has been applied. The resulting color values are linear, but they are still output-referred and should not be combined with scene-referred linear images.
Color Managing Rendered 3D CG Images
Images rendered from 3D scenes created in an application such as Maya are typically scene-referred linear RGBA images in a floating-point format such as OpenEXR.
Color Managing Matte Paintings
All compositing should be done in a scene-linear color space, and this includes composites with painted matte backgrounds. However, matte paintings can be produced using different techniques, and these affect how you should process the images.
Color Managing Textures and Maps
3D CG elements should be rendered using a scene-linear working space. However, when you are manually specifying color transforms for images that are used for textures and other maps, they should be processed in various ways depending on both the image state and the type of map.
Color Management and Image-based Lighting (IBL)
The algorithms used to render 3D CG graphics require scene-linear colors, and images intended for image-based lighting are typically supplied as HDR or OpenEXR images that are scene-linear already. However, the images might still require some color management.
White Point Conversion
The white point determines the color balance of an image. When you are manually specifying color transforms, the white point may need to be adjusted depending on both the illumination of the original scene and the conditions under which the output is viewed — this process is also variously known as chromatic adaptation, white balancing, gray balancing, or neutral balancing.
Using Diagnostic Color Transforms
There are some transforms in the levels/ directory that you can apply to the display to show potential problem areas in images.
Converting Images Between 12i or 16i and 16f Encodings
It is often useful or necessary to convert 12-bit integer (12i) or 16-bit integer (16i) to 16-bit floating-point (16f) encoding or vice-versa. When round-tripping between encodings like this, it's important that the transforms are as lossless as possible to avoid image degradation.
Custom Color Transforms
Autodesk Color Management lets you create your own .ctf files to define custom color transforms.
A Complex Color Management Example
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 showing the transforms that you can manually specify to accomplish a specific goal.

Parent topic: Autodesk Color Management — Supplemental Information