What a LUT actually is
A 3D LUT is a lookup table: for a grid of input colours, it stores the colour that should come out. A 33-point cube holds 33 × 33 × 33 = 35,937 entries, and every colour that falls between grid points is interpolated from the eight corners surrounding it. That is trilinear interpolation, and it is exactly what this page does.
The file format is plain text, which is why you can open a .cube in a text editor:
| Line | Meaning |
|---|---|
| TITLE "Kodachrome 64" | Optional name |
| LUT_3D_SIZE 33 | Grid points per axis |
| DOMAIN_MIN 0 0 0 | Input range floor — rarely anything but zero |
| DOMAIN_MAX 1 1 1 | Input range ceiling |
| 0.0134 0.0102 0.0089 | One RGB triplet per grid point, red index changing fastest |
Where LUTs go wrong
Log LUTs on normal photos
A conversion LUT expects flat, low-contrast log footage and adds all the contrast back. Feed it an ordinary JPEG that already has contrast and it will crush the shadows and blow the highlights. If the result looks violent, that is usually why. Look-style LUTs built for display-referred images behave properly here.
Banding in the sky
An 8-bit JPEG has 256 levels per channel. Any LUT that stretches part of the tonal range spreads those levels further apart, and smooth gradients start to step. It is not the LUT's fault and it is not this tool's — it is the bit depth. The same grade on raw or log footage holds together.
Intensity is not the same as subtlety
Dialling a LUT to 40% blends towards the original linearly, which softens everything at once — including the parts that were working. Often a gentler LUT beats a strong one at reduced strength.
In the app the same grade runs live in the viewfinder at capture time, so the clipping warnings and the histogram describe the graded image — the frame you are actually making, not a neutral version of it you would then have to imagine.
Common questions
What is a .cube file?
A plain-text 3D lookup table that maps input colours to output colours. It is the most widely supported LUT format, readable by Resolve, Premiere, Final Cut, Photoshop and most camera apps that accept custom looks.
Is my photo uploaded?
No. The image is drawn into a canvas in your browser and the LUT is applied in JavaScript on your machine. This site has no backend to upload to.
Why is the preview smaller than my photo?
Large images are downscaled to a working size so the grade stays interactive as you move the sliders. The download matches what you see. For a full-resolution export, apply the LUT in your editor — this tool is for judging a look, not finishing a file.
Does it support 1D LUTs?
Yes. A .cube with LUT_1D_SIZE is a per-channel curve rather than a colour cube, and this tool applies it with linear interpolation along each channel.
Can I use these LUTs on my iPhone?
Not in the stock camera app. Lucid Camera imports .cube files and applies them live in the viewfinder, with the option to bake the grade into the saved file or keep it as preview only.
Related tools
Your LUTs, live in the viewfinder.
Import any .cube into Lucid and shoot through it — graded preview, graded histogram, graded zebra, and your choice of baking it in or keeping the negative clean.