LUT — Look-Up Table
Definition
A LUT (look-up table) is a table that maps input colour or brightness values to output values; it is applied to a video signal to convert it or to change its look. Technical, or transform, LUTs convert between colour spaces or transfer functions, for example from a camera log format to Rec.709 for correct display. Creative, or look, LUTs apply a graded aesthetic. A 1D LUT modifies each channel curve separately, while a 3D LUT remaps the whole RGB colour cube and can therefore change hue, saturation and luminance together.
In the field
A log camera feed looks flat and washed out until a log-to-Rec.709 LUT is applied, after which it displays correctly on the wall and the monitors. Technical LUTs are applied before creative ones: a look LUT placed before the colour space and gamma transform works on the wrong values, and the resulting colour errors cannot be recovered further down the chain.
Sources
- Wikipédia, 3D lookup table : LUT 3D indexée par les valeurs RVB d'entrée, employée en étalonnage et en conversion d'espace colorimétrique (pointeur secondaire) · en.wikipedia.org
- Wikipédia, Log profile : enregistrement log des caméras et conversion par LUT vers l'espace d'affichage (pointeur secondaire) · en.wikipedia.org
- Wikipédia, Color grading : étalonnage, corrections techniques et look créatif (pointeur secondaire) · en.wikipedia.org