What does lut mean?

LUT refers to a look-up table, which is essentially a memory. It writes data into RAM in advance, and every time a signal is input, it is equivalent to inputting an address lookup table, finding out the content corresponding to the address, and then outputting it.

LUT has a wide range of applications. For example, LUT (Look-up Table) can be applied to the mapping table of pixel gray values. It converts the actual sampled pixel gray value into another corresponding gray value through certain transformation, such as thresholding, inversion, binarization, contrast adjustment and linear transformation. , can highlight the useful information of the image and enhance the optical contrast of the image.

Many PC series cards have 8/10/12/16 or even 32-bit luts, and the specific conversion in luts is defined by software. The most important significance of LUT here is that it is compatible with the high-order display function of ordinary displays, so that the wide color gamut (generally exceeding srgb) that ordinary displays cannot display can be roughly simulated on ordinary displays as much as possible.

However, the effect of lut simulation can only be used as a reference, and it can be used as a general impression when retouching. The best and most complete presentation is still that the indicators of the display, the graphics card and the material itself are highly consistent, which is called "hard decoding".

The difference between LUT color matching and filter:

Although both LUT color matching and filter can improve the picture in the software, LUT color matching can find new colors by changing the value of RGB in the color lookup table, which is a kind of color space conversion and a kind of file, and data such as hue, lightness and saturation can be modified at will, so only specific production software can use LUT color matching.

Filters can be used in general editing software. By changing exposure, contrast, hue, color temperature, etc. , which is more limited and relatively simple than LUT color matching.