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Filmmaking Dictionary: Number 3 / 3D LUT
Definition
A 3D LUT, or three-dimensional lookup table, transforms colour values using a grid whose three input dimensions are red, green and blue. The output for a colour can depend on the combination of all three components.
The ‘3D’ describes a colour-value grid. It does not refer to stereoscopic pictures, three-dimensional objects or a special depth effect.
How It Differs From a 1D LUT
A 1D LUT typically maps each colour channel independently. A 3D LUT can describe interactions between channels, making it useful for more complex colour transforms and creative looks. Software interpolates between the stored grid points to calculate values that do not fall exactly on a sample.
For example, a 33-point cube has 33 sample positions along each input dimension, producing 35,937 grid points. That count is not the image’s bit depth and does not by itself prove that the LUT creates a better result than another transform.
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Input and Output Must Match
A LUT made for a particular log encoding and colour gamut expects that type of input. Applying it to a different camera encoding or to footage already converted for display can produce excessive contrast, incorrect colour or clipped-looking highlights.
The output expectation matters too. A viewing transform intended for one display space is not automatically the correct final transform for every master. Label the LUT and its intended purpose clearly.
Practical Example
A cinematographer approves a monitoring LUT during tests. The camera records the original log image while the monitor applies the look. Editorial needs the same viewing information, but it also needs to know whether the look is only metadata or has been baked into a proxy. Applying it twice changes the picture.
What a LUT Does Not Replace
- It does not correct every exposure or white-balance error.
- It does not restore information lost through clipping.
- It does not automatically match different cameras or lighting conditions.
- It does not replace calibrated monitoring or a managed colour pipeline.
- It does not describe masks, tracking or every operation used in a finished grade.
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Frequently Asked Questions
Is a larger LUT grid always better?
No. Grid size, interpolation, input range and the transform itself all matter. The receiving device must also support the file.
Can a LUT include both a technical transform and a look?
Yes. That is why its intended input, output and creative role should be documented.
Related Terms
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