In information technology a LUT (Look Up Table) is a table containing values which have access to various applications. Instead of saving the complete set of information on the colour values in one file, the system merely refers to the table. The colour value is precisely defined in the table. Thus, there is no need to measure the exact position.
In computer graphics, CLUTs (Color Lookup Table) are another concept. Here, all colours are stored in an indexed graphics file. An indexed graphics file is used to save memory space for images which are not rich in colour. The colour values are defined in the CLUT and recorded on a colour table. The colour table consists mostly of RGB, where the intensity of the colour system is established between 0 and 255.
With the aid of the index, which represents a list or look-up table of sorted terms, the colours in the table are assigned. One example is the halftone image where one pixel is allocated a number. This grey value can take on the bit-formed conditions between 0 and 255. These values are also referred to as the indices of a colour table. These are assigned to the LUT. Indexed images are highly efficient when used correctly.
There are also 3D Look Up Tables (LUT), which are used on the EIZO CG232W, for example. These guarantee the highest image quality because of the colour management system, which has 12-Bit length per colour channel and 16-Bit colour processing. The 3D Look Up Table (12-Bit per RGB) and a special switching circuit (Digital Uniformity Equaliser) correct irregularities automatically, pixel by pixel.
When examined more closely, the grey gradients are reproduced edgelessly and colour transitions are displayed without stripes. Thus, a soft, fluid gradation reproduction and a grey axis without colour deviations should be guaranteed. A 3D LUT is defined as a 3D grid where each axis represents an entry point for one of the three colour components. Output values from the 3D LUT are interpolated between the 8 next points of the grid.
LUTs are used especially widely in post-production in the TV/video sectors and also for professional photo editing in order to avoid colour changes in the gradient. They ensure originality between processing and the end result. 3D Look Up Tables allow for a perfect simulation of CYMK print output.