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Light Trim Node

By Kriss Norde

The Light Trim node adjusts the exposure of an image in printer points, the traditional unit of the film lab. Designed to work on material in Cineon logarithmic space, it allows an overall or per-channel R/G/B density correction, just as a telecine or a film colorist would do it.

Overview

Light Trim is designed for working in log (typically after a Cineon Log Lin → Log, or on a native log DPX). It operates in printer points - the log equivalent of a relative exposure in stops, with the traditional resolution of the film lab.

Master Trim changes the overall exposure, Red/Green/Blue Trim each channel individually = white balance / color cast correction. More natural and precise than adjusting Gain or Lift in linear for this kind of correction.

Where to find this node

  • Effects Library: Tools > Film > Light Trim
  • Quick add: right-click in the Node Editor → Add Tool > Film > Light Trim

Printer points explained

A printer point (PP) is the unit used by traditional film printers (Bell & Howell, Hazeltine). A 0-50 scale (sometimes 1-50) sets the print density per R/G/B channel.

Approximate conversion
1 stop of exposure ≈ 12 printer points. So 6 PP ≈ 1/2 stop, 24 PP ≈ 2 stops. Lets you think in photographic terms while staying in the language of the lab.
Polarity
Positive value = more light (brighter image). Negative value = less light (darker image). Note: on a classic telecine the polarity can be reversed depending on the convention.
Color balance
Adjusting Red Trim alone = warm/cool on the R channel, Green Trim = green/magenta, Blue Trim = blue/yellow. Combined = precise white balance.

Inputs

  • Input (orange) - the 2D image in log to correct. Applying it to linear material gives unusual results.
  • Effect Mask (blue) - optional. Limits the correction to an area.

Setup

Regrading the density of a log shot:
MediaIn (log DPX) → Light Trim (Master +5 PP, Blue Trim -3)
                  → MediaOut (log DPX)

Lin workflow with Cineon Log:
MediaIn (lin) → Cineon Log (Lin to Log)
            → Light Trim (corrections)
            → Cineon Log (Log to Lin)
            → MediaOut (lin)

Matching density between two archive shots:
Shot A → Light Trim (calibrated on a reference)
Shot B → Light Trim (calibrated on the same reference)
Merge → MediaOut

Controls tab

Master Trim (default: 0)
Overall exposure adjustment in printer points. +12 ≈ 1 stop brighter, -12 ≈ 1 stop darker. Affects all 3 channels evenly.
Red Trim / Green Trim / Blue Trim (defaults: 0)
Independent trims per RGB channel. They allow a balance correction or compensating a color deviation in the scan / negative.
Conversion Type (default: Cineon)
The conversion system used. Cineon: standard Kodak curve (10-bit log). Custom: lets you adjust Black/White Reference and gamma for non-standard stocks.
Black Reference / White Reference (Cineon defaults: 95 / 685)
Cineon log bounds used for the internal conversion. Adjust them if the source material uses a different range (custom scan).
Gamma
Gamma of the simulated film's response curve. Kodak Cineon standard = 0.6.

Use cases

  • Regrading film scan density - correct a slightly under/overexposed log DPX scan with Master Trim, without going through a log-specific Color Corrector node.
  • Color matching between film stocks - compensate the cast of a specific stock (e.g. Vision3 vs Eastman) with Red/Green/Blue Trim.
  • Telecine correction - traditional TC pipeline: Light Trim faithfully reproduces the classic telecine console for preview or conform.
  • Authentic vintage workflow - work in the same unit as traditional film colorists to reproduce their period settings.
  • Easy per-shot correction - fast and physically based for adjusting one shot in a sequence without touching the overall look.
  • Negative density compensation - old, degraded negatives (loss of density) → a positive Light Trim compensates for the underexposure caused by the age of the material.

Tips

  • Always work in log - Light Trim is physically designed for log data. On lin, the results will not follow printer conventions.
  • 1 stop = 12 PP (cheat sheet) - to translate a photographer's reflex to this node: +1 stop = +12 PP, -2 stops = -24 PP.
  • Do not stack it with a log Color Corrector - pick one or the other to keep the chain readable. Light Trim for basic regrading, Color Corrector for more creative adjustments.
  • Safe round trip - Cineon Log (Lin to Log) → Light Trim → Cineon Log (Log to Lin) with the same parameters = identity when all the trims are at 0.
  • R/G/B trims on an 18% gray - for a neutral white balance, sample an 18% patch in the image and adjust R/G/B Trim to bring each channel to the same log value (~445 on a 0-1023 scale).
  • Float bit depth recommended - in 32-bit float, adjustments stay clean even beyond the 0-1 range.
  • For modern ACES workflows, prefer ASC CDL or Color Space Transform with a primary correction over this node (which remains tied to legacy Cineon).