LUTs explained: what a .cube file actually does, and how to use one on AI footage
A LUT is a lookup table: a list of what every colour should become. It is not a filter, not a grade and not magic, and once you know what it does you know when to use one, when to turn it down, and why it cannot fix a shot that was never lit.
Every editing tool has a menu of looks, and somewhere near it a button that says Load LUT. The looks are easy. The LUT button is where people either get a cinematic grade in one click or wonder why their footage turned green. The difference is knowing what the file actually does.
A LUT is a lookup table
LUT stands for look-up table, and that is the whole technology. A .cube file is a list: for this input colour, output that colour. A 3D LUT does it for red, green and blue together, on a grid (33 points along each axis is common, which is why the file is a few hundred kilobytes of numbers), and the colours between the grid points are interpolated. There is no understanding of the image in it. A LUT does not know what a face is, where the sky is, or that the shot is underexposed. It moves colours, every pixel the same way, and it does so instantly, which is what makes it useful.
Two kinds exist and they are often confused. A technical LUT converts between colour spaces: from a camera's flat log recording to a normal-looking image, for instance. A creative LUT is a look: teal shadows and orange skin, faded blacks, a cool wash. Camera makers and film-stock brands publish both; the free packs you find online are nearly all creative ones, and they are built to be applied to an image that already looks normal.
That last sentence is the one that matters for AI footage.
Why a LUT behaves differently on AI footage
Generated clips do not come out of a camera. They arrive already looking the way the model thought a finished shot looks: contrast in place, colours saturated, skin already warm. Apply a creative LUT designed for a flat camera image to that and you are grading a graded image. Shadows crush, skin goes orange, highlights clip. The LUT is doing exactly what it says; the input was never what it expected.
So the order is the opposite of a camera workflow. Balance first, flavour second, and the flavour at a lower strength than the pack suggests.
How to use one here
Grade after the cut is locked: colour is easier to judge in context, and trimming re-grades nothing.
- Balance the clip. Effects → Color has brightness, contrast, saturation and temperature per clip. Bring a too-warm shot back toward neutral, pull the saturation down a touch, and get the exposure right. This is the step most people skip, and the reason their LUT looks wrong.
- Load the LUT. Effects → Color LUT takes any standard .cube file; the free packs from camera and film-stock vendors all load. The preview runs a true 3D lookup on the GPU, so what you see is what renders, including the aggressive ones.
- Turn the intensity dial down. Start at about half. A LUT at full strength is the author's taste on the author's footage; at 40 to 60% it is a direction on yours. Blend until the skin looks like skin.
- Apply the same LUT to every clip in the sequence. Per-clip balance, one LUT across all of it. That is what makes a run of shots from different models and different prompts read as one film. Why your AI shots don't match is the long version of this problem.
One thing worth knowing: the LUT is applied after chroma keying, so a creative grade never breaks a key.
When a look is the quicker answer
The six built-in looks (B&W, Noir, Sepia, Vintage, Vivid and Muted) stack on top of your balance pass the same way a LUT does, and for most social work one of them plus a temperature nudge is the whole grade. Reach for a .cube file when you need a specific film's look, a brand palette you have been given as a LUT, or a match to footage someone else graded.
What a LUT cannot do
A LUT moves the colours that are there. It cannot put light where there was none, recover a sky that clipped to white, sharpen a soft take, or change the time of day. For those there are the AI looks in the same panel: colourise black-and-white footage, day to night, deblur, and relighting a shot from a direction you describe. And when the problem is the content rather than the colour, that is a restyle, not a grade: How to restyle real footage with AI.
The rule of thumb: if you can describe the fix in terms of colour, it is a grade or a LUT. If you need the word "light" or "where", it is an AI look. If you need the word "instead", it is a restyle.
A note on the green
If a LUT turns your footage green, you have a technical LUT, built to convert one camera's log footage, applied to a normal image. It is not broken; it is expecting an input you did not give it. Delete it and find a creative LUT from the same pack.