Tutorials Video

What a LUT File Actually Contains and Does

By Infinite Creation · Intermediate · ~12 min

A 1960s mid-century comic book style editorial illustration showing a video editor and a director reviewing the cut together, with a colour grading panel with trackballs, a camera on a tripod visible in the frame.

Overview

A LUT is often talked about as if it were a mysterious 'filter,' but it's structurally a fairly simple, specific thing: a lookup table mapping input color values to output color values, and understanding that structure directly explains why a LUT designed for one type of footage can look wrong on differently-shot footage.

Steps

The simple version: a LUT is a color conversion recipe

At the simplest level, a LUT takes an input color value (for a given pixel) and outputs a different, transformed color value according to a fixed rule, applying it to a whole image or video simply means running every pixel's color through the same conversion rule.

What's really inside the file: a grid of input-to-output color mappings

Technically, a LUT file contains a three-dimensional grid of specific input color values (say, a sampling of possible red/green/blue combinations) each mapped to a corresponding output color value, with the software interpolating (estimating) the correct output for any input color that falls between the specifically-defined grid points rather than storing every possible color combination individually.

Why a LUT is designed around a specific input color range

Because a LUT's grid points are defined around specific expected input values, it's designed with a particular source color range in mind, often a specific camera's flat or log picture profile, which compresses the camera's full dynamic range into a predictable, narrow color range that the LUT's grid was built to transform correctly.

Why the same LUT can look right on one shot and wrong on another

Footage shot with different exposure, white balance, or a different picture profile than what the LUT's grid was designed around feeds input color values into the lookup table that fall outside or at the edges of its intended range, which the interpolation handles less predictably, producing the clipped, oversaturated, or oddly-colored results that make a popular LUT sometimes look wrong on footage it wasn't specifically designed for.

Pro Tips

Shoot in the specific flat or log picture profile a LUT was designed for, and expose consistently, so your footage's color values actually fall within the range the LUT's grid was built to handle correctly.
If a LUT looks wrong on a specific shot, check whether that shot's exposure or white balance differs from your other footage, inconsistent capture settings are a common reason the same LUT behaves differently across a project.
Treat a LUT as a starting point requiring further adjustment per shot, since even correctly-exposed footage will have some natural shot-to-shot variation the LUT's fixed grid can't perfectly account for.

Tested: how grid size changes a LUT's accuracy

We wrote one colour transform as a .cube LUT at the three common grid sizes, 17, 33 and 65 points per side, and ran 200,000 random 16-bit colours through the lut3d filter in FFmpeg 8.1.2 on 2026-09-23. The transform is an S-curve on each channel followed by a 1.2 times saturation increase. We then compared every output with the exact result of the same maths. Errors are in 10-bit code values, where one step is 1/1023 of full scale.

Grid	Colours stored	File size	Interpolation	Mean error	99th percentile	Worst
17 points	4,913	0.13 MB	trilinear	1.15	12.3	20.4
17 points	4,913	0.13 MB	tetrahedral	1.06	11.1	19.8
33 points	35,937	0.97 MB	trilinear	0.28	4.1	10.4
33 points	35,937	0.97 MB	tetrahedral	0.26	3.6	9.9
65 points	274,625	7.41 MB	trilinear	0.07	1.3	5.2
65 points	274,625	7.41 MB	tetrahedral	0.07	1.1	5.0

Each doubling of the grid cut the mean error to about a quarter. With tetrahedral interpolation the mean fell from 1.06 steps at 17 points to 0.26 at 33 and 0.07 at 65. The worst colours only halved each time, from 19.8 to 9.9 to 5.0 steps. Those colours sit where the curve bends hardest, between grid points, which is where step 2 says the software estimates.

Tetrahedral interpolation beat trilinear at every size, by a small margin. FFmpeg uses tetrahedral unless you ask for something else. The 65-point file was 7.41 MB against 0.97 MB for 33 points: about eight times the data for a quarter of the error. For a smooth grade, 33 points keeps the average error well under one 10-bit step.

To apply a .cube LUT with tetrahedral interpolation in FFmpeg: ffmpeg -i clip.mov -vf lut3d=file=grade.cube:interp=tetrahedral -c:v prores_ks graded.mov

Validated. Measured 2026-09-23 with FFmpeg 8.1.2 on macOS, Apple silicon. 200,000 colours from a seeded random generator, 16-bit in and out.

Knowledge Base

What You'll Learn

A LUT is structurally a grid of specific input-to-output color mappings designed around a particular expected source color range, and understanding that structure explains why the same LUT can look correct on some footage and wrong on differently-shot footage.

The Plain-English Version

A LUT is a fixed color conversion recipe built assuming your footage's colors fall within a specific expected range, usually a particular flat or log camera profile, and applying it to footage shot differently is like using a recipe's exact measurements on a different-sized batch of ingredients: the proportions don't line up the same way.

The Misunderstanding This Clears Up

People sometimes expect a single LUT to work as a universal, one-size-fits-all filter for any footage, but a LUT's grid is built around a specific input color range, which is exactly why this site's LUT myth-busting tutorial emphasizes correct exposure and picture profile as prerequisites, not optional extras.

Where This Fits

A LUT is a fixed transform, and Color Grading in DaVinci Resolve shows where one belongs in a grade and where a node does the job better.

FAQ

Q: Why does the same LUT look different on different shots in my project?
A: A LUT's color grid is built around a specific expected input range (often a particular camera's flat or log profile, exposed a specific way), so shots with different exposure, white balance, or picture profile feed input values into the lookup table that fall outside or at the edges of its intended range, producing less predictable results.

Q: Can I edit or create my own LUT?
A: Yes, color grading software can export the color adjustments you make on a reference shot as a new LUT file, effectively capturing your own grid of input-to-output color mappings, though it will carry the same range-specific limitation as any other LUT when applied to differently-shot footage.