The one-sentence version
A LUT — lookup table — is a file that says what every colour should turn into. Feed it a slightly green shadow and it returns a neutral one; feed it a flat grey sky and it returns a blue one. Nothing is calculated at the time; the answers were worked out in advance and written down.
What is actually in the file
Open a .cube in a text editor and it is readable:
TITLE "Teal & Orange"
LUT_3D_SIZE 33
0.000000 0.000000 0.000000
0.031250 0.000000 0.000000
...LUT_3D_SIZE 33 means the table is a 33 × 33 × 33 cube — 35,937 entries, one
for every point on a grid through red, green and blue. Each line is the output
colour for one grid point.
Your photo does not contain only those 35,937 colours, so a LUT is not a dictionary lookup. The renderer finds the eight nearest grid points around a pixel's colour and interpolates between them, which is why a 17-point LUT can band on a smooth sky where a 33 or 65-point one does not.
| Size | Entries | In practice |
|---|---|---|
| 17³ | 4,913 | Small, fast, can band on gradients |
| 33³ | 35,937 | The common size, and a sensible default |
| 65³ | 274,625 | Precise, large files, mostly for conversions |
Two jobs, one file format
This is the distinction that causes most of the trouble, because both arrive as
.cube and nothing in the file says which it is.
Conversion LUTs are technical. They map a camera's flat recording curve back to a normal one: D-Log to Rec.709, S-Log3 to Rec.709, C-Log, GoPro's flat profile. There is a right answer, and it is the one built for the exact gamma and gamut the camera recorded.
Creative LUTs are a look. Teal and orange, bleach bypass, a film emulation. There is no right answer, only whether you like it.
The order matters: conversion first, look second. A creative LUT applied to flat footage produces something that looks nearly right and falls apart the moment anyone grades it further.
Why a LUT is not an edit
A LUT knows nothing about the picture. It cannot tell a face from a wall, and it maps the two identically if they happen to be the same colour. That is why:
- A LUT cannot fix exposure. Feed it a clipped highlight and it returns a mapped clipped highlight. Nothing was recorded there to recover.
- A LUT cannot fix white balance, not really. It can push a cast in another direction, which is a different thing from correcting it.
- Strength is your control, not the LUT's. A look at 100% is what its author intended for their footage. On yours, 60% is often better, and that has nothing to do with the quality of the LUT.
Where LUTs go wrong
Applied twice. The most common one. A conversion in the camera profile and the same conversion in the edit, and the result is dark and crunchy in a way nobody can put their finger on.
Wrong gamut. A LUT built for S-Gamut3.Cine on S-Gamut3 footage is not a disaster, it is just subtly wrong — which is worse, because it survives review.
Malformed files. Some DJI .cube files declare their size with a tab rather
than a space, and ffmpeg rejects them outright. The file is fine; the parser is
strict. Any tool that does not read around this will tell you your LUT is
broken.
Judged on the wrong image. A look chosen on the vendor's sample and applied to your own material rarely behaves the same. This is why previewing on your own frame matters more than any thumbnail a pack ships with.
Applying one, and applying four hundred
For a single file every editor does it — the mechanics are in adding LUTs in DaVinci Resolve and the Premiere workflow.
For a shoot, the tools start asking for a project, a timeline and a render
queue, and the strength control becomes per-clip work. That is the gap
BatchTone fills on macOS: one .cube across photos and video at once, a
strength dial on every file, and malformed files repaired on the way in. There
is a seven-day trial.
Common questions
Is a LUT the same as a preset?
No. A preset is a set of slider positions in a particular application — exposure, contrast, curves — and it can be undone one slider at a time. A LUT is a fixed colour mapping, and it is the same in every tool that reads it.
Does a LUT work the same on photos and video?
The mapping does. The surrounding pipeline may not: video is usually 8 or 10-bit in a limited range, and photos are often full range, so the same LUT can land slightly differently unless the tool handles the range explicitly.
Why does the same LUT look different in two apps?
Usually interpolation and colour management. Some tools interpolate between grid points more carefully than others, and some apply the LUT in a different colour space than the one it was authored in.
Can I make my own?
Yes — grade a reference image the way you like in almost any colour tool and
export the result as a .cube. Where to find existing ones, and which are worth
having, is covered in free LUTs.