2017

NOTE The camera/Canon/Technicolor_CineStyle_to_HD-video.ctf is a special transform for viewing and outputting
video that was shot using the Canon CineStyle picture style.
Camera Black
Footage from digital cinema cameras can contain negative values in the noise around black. These negative
values can cause problems during image processing, especially when adjusting hue and saturation.
All of the input transforms supplied with Autodesk Color Management for input from various cameras map
negative values to small positive values losslessly. If you prefer to undo this correction and deal with the
negative values in another way, you can apply the remove_camera_black transform after the camera input
transform.
In other cases, you may receive images that have already had a third-party input transform applied, but still
have negative values. In these cases, you can use the apply_camera_black transform to map the negative
values to small positive values.
Color Managing Video Footage
When 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.
There are a few options to convert these images to a scene-referred linear state:
■ If the footage is HD (Rec. 709), you can apply HD-video_to_ACES from the RRT+ODT directory.
■ Alternatively, you can apply an inverse tone map such as tone-map/inversePhotoMap_gamma_2.4. This
will not be exact if the footage was originally shot as video or converted with a different tone map, but
it can be a good approximation that works well in many cases.
SMPTE Legal Video Levels
Digital video standards use integer pixel encodings, and typically define a reference black and white level
such that there is some headroom and footroom left for values to exceed these levels without being clipped.
For example, SMPTE 10-bit digital video places reference black at 64 and reference white at 940. Broadcasters
often have requirements that content provided to them not exceed these "legal" limits. (Note that the precise
definition of "legal" varies depending on the video format and broadcaster.)
Software applications that work with integer pixel encodings often follow a different convention which
places black and white at the minimum and maximum values allowed by the integer (e.g. for the 10-bit
case, black at 0 and white at 1023).
When converting between video and computer encodings, it is necessary to decide whether to keep the
headroom and footroom (in which case black and white are not quite where they are expected on the
computer), or to discard the headroom and footroom and map the reference video black/white to the
computer black/white.
Typically, this choice is made as part of the video I/O process and is applied in the video hardware. However,
it is sometimes useful to also have color transforms available so that the conversion may be performed
elsewhere in the workflow.
The full-range_to_legal_10bit transform in the levels/ directory scales, offsets, and clamps computer color
values (i.e. 0 to 1023) so that they are within the legal SMPTE video range for broadcasting (i.e. 64 and 940).
The legal-range_to_full_10bit transform inverts that operation.
Autodesk Color Management | 1315