OpenEXR is a high-dynamic range (HDR) media format supporting multi-resolutions and an arbitrary number of channels and channel types, such as specular, diffuse, alpha, RGB, normals, in a single file. Lustre supports OpenEXR 16-bit RGB only (files with other channels cannot be read). This format is sometimes referred to as “16-bit half float”.
Lustre can obtain 16-bit floating point media in two distinct ways. First, it can acquire the media by way of a Wiretap server. That is to say, by browsing the clip libraries and associated framestores of Visual Effects and Editing applications. Second, it can acquire the media directly, by importing OpenEXR media using a Wiretap Gateway server. In both cases, you need to tell Lustre how to work with the half float media.
As indicated, OpenEXR represents pixels as floating-point numbers. Internally, Lustre uses a 16-bit integer format. Thus, before you can grade OpenEXR media, it must be converted from floating point to integer. This is done by setting a floating point conversion LUT for the project. See Applying an Existing Input LUT.
Two special floating point conversion LUTs and one output LUT have been provided for this purpose. Before working with OpenEXR media, select the conversion LUT corresponding to the colour space defined for the project.
| LUT | Description |
|---|---|
| lin_default | The default linear colour space input LUT, generally reserved for video images. |
| log_default | The default logarithmic colour space input LUT, generally reserved for film images. |
| identityExtended | An output LUT designed to preserve the floating point media. |
When rendering to Wiretap as part of an interoperability workflow with an Autodesk Visual Effects and Finishing application, apply the inverse LUT, identityExtended, during the render, to restore the original colour space. If interoperability is not the goal, specify an output format and render as usual, without applying an output LUT. See Rendering Shots.
