LightTrim

LightTrim belongs to Film nodes. Its name refers to film-scanner light adjustments: the tool is designed primarily for logarithmic data such as Cineon, camera Log and appropriately decoded RAW. It does not isolate highlights or control Glow size.

Check the space immediately at the node input. A RAW extension or flat appearance does not prove Fusion receives Log: the project may transform footage earlier. If the input is already Linear or display-referred, establish the pipeline first; do not add reverse conversions merely to use this node without a clear purpose.

The manual’s order is Log clip → LightTrim → CineonLog. The final node decodes the transfer curve rather than automatically solving the camera’s complete color system. Align gamut, linear working space and display conversion separately for correct viewing and compositing.

Trim 0 is the neutral starting point. BMD defines eight printing points per stop; four points are half that scale. This changes exposure representation rather than reconstructing detail clipped during capture. Evaluate outputs through the same technical conversion.

Lock R/G/B/A is enabled in the source capture. One Trim is convenient for a common adjustment, but RGBA also includes alpha: inspect it separately. For channel work, apply deliberate RGB trims and leave Alpha unchanged unless the matte requires adjustment.

The blue Effect Mask is applied to the processed result. It supports local exposure adjustment and does not convert the RGB output into a mask stream. Inspect the transition and motion at a soft mask boundary, especially when exposures differ substantially.

Trim can be animated with explicit keys. Use that animation for an exposure task, such as smoothly compensating a lighting change within a shot. Inspect the curve and entire decoded range; matching first and last values does not guarantee a smooth transition between them.