3D color lookup table mapping input colors to predefined outputs — faster than curves for real-time color science. Essential for camera LUT or grading LUT workflows.
CLUT (Color Lookup Table)
You stand in front of the camera, and the sensor pipeline has to decide in milliseconds: How will this red be rendered? Which shade of blue fits the final color profile? This is where the Color Lookup Table comes in — a three-dimensional mathematical matrix that maps input colors directly to output colors, without any curve calculations.
Practically, it works like this: Instead of the monitor or camera running every pixel through curve algorithms live (expensive, slow), the CLUT interpolates between pre-calculated color values. You feed it input coordinates (R, G, B) and immediately get the corrected output values — real-time color encoding without a CPU bottleneck. On set with the DCI monitor, you no longer need 300ms latency; the LUT renders your Log images into the Rec.709 color space while you're still monitoring the take.
This makes CLUTs indispensable for two workflows: Firstly, in-camera application — many digital cameras record internally in RAW or Log, but show you a pre-calculated color image in the EVF via CLUT, so you're not working blind on a flat Log image. RED, ARRI, Sony use this as standard. Secondly, in real-time grading — while you're at the editing station or on the DCI reference monitor, the software loads a 33x33x33 or 65x65x65 CLUT and applies it to your timecode. This is faster and more memory-efficient than rendering curve stacks.
The quality of the CLUT depends on its resolution — a small table (17x17x17) is fast but coarse; a larger one (65x65x65) costs memory but calculates more precisely. In grading, you notice this particularly in the mid-tones and with fine color transitions. Some color tools allow you to export CLUTs and integrate them into other software or camera profiles — this is the practical workflow when you carry over look decisions from set to the DI suite.
Related, but not identical: LUT (Look-Up Table, often 1D), 3D-LUT (identical to CLUT, just different terminology), and color calibration in monitor setup. CLUTs are the tool of real-time color — precise enough for final color, fast enough for the live session.