A LUT is basically a table that says if the input is 1 make the output 7. If the input is 0 make the output 5 – or whatever, these numbers are arbitrary, it is just a conversion matrix – take this, make it that. This can happen to the image over all or per colour channel (RGB). For example in the red channel use LUT A to make 1 = 7 but in the blue channel use LUT B to make 1=15.
What’s the difference between a 1D-LUT and a 3D-LUT?
With a 1D-LUT you’ve got some control, but not that much control. So if you increase contrast in your image, you will increase saturation, because the values are tied together in the simple chart, take this and make it that.
With a 3D LUT you have more control over transforming these values separately and in combination. Here you can create “a set of the combination of three inputs defining the combination of R, G, and B values; not of one where each input refers to one unique output”. This allows for greater control, for example, increasing contrast without increasing saturation.
What are the different types of LUTS for?
Colorist Patrick Inhofer divides LUTS into Technical LUTS and Creative LUTS.
Technical LUTS – These types of LUTs are designed to transform an image from one colour space / gamut to another. The end goal is to have the same image look perceptually identical on two different viewing devices. [A perfect match every time]
Creative LUTS – These types of LUTs can be generated in software, allowing, for instance, completely different grading apps to share looks between them. [These are the types of LUTS you’re thinking of when you think about LUTS – a cool Look]
Sources: https://jonnyelwyn.co.uk/
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