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3D LUT Explained

A 3D LUT is a table of color values that converts any input color value into a corrected RGB triplet output color value. The 3D LUT analyzes the proximity of a displayed color to its reference value and provides a corrected value that adds or removes what is missing to get closer to a desired color space standard. This corrects the display's output to adhere to a specified white point and color gamut when the 3D LUT is active.

A 3D LUT is a more precise method of color correcting a display compared to traditional display-based grayscale calibration, as 3D LUTs offer the potential creation of thousands of individual calibration points that can be used to interpolate any color value that can be created by the display. A typical digital display by comparison relies on a limited number of calibration points to interpolate all color values that are controlled by a limited set of color controls.

Visual Representation of a 3D LUT

Luminance adds volume to a chromaticity diagram.
This creates a 3D cube like the RGB cube below:

Image

Any color space (e.g. XYZ) can be represented inside the cube.
Luminance (black to white) creates uneven color distribution:

Image

A 3D LUT is capable of correcting the three main aspects of display calibration:
  • White Point: Finding the achromatic point (D6500) and maintaining it from reference black to peak white (0 to 100% white) with the right balance of red, green and blue.
  • Primaries: Combining values of red, green and blue to create the values placed on the corners of a triangular color gamut. These primary colors are used as the base to create all other colors.
  • Transfer Function: Producing gamma-corrected or perceptual quantization-corrected (PQ) luminance values. A capture device converts light to voltage. A display converts voltage to light for each pixel using a transfer function suitable for the gamut luminance range.

Manual grayscale calibration is only focused on adjusting the controls that directly influence the above qualities. If the display was perfectly linear — where any input signal produced a 100% predictable change in displayed color — a grayscale and primary color calibration would produce a perfect result. The problem is almost no consumer displays are perfectly linear and suffer from some color cross-coupling and a lack of RGB separation. A 3D LUT does not have to focus exclusively on the grayscale and primary colors and can treat all colors profiled within the cube equally to correct colors found between the white point and gamut edges. 3D LUT corrections use a small amount of GPU power, but can produce near-reference color when combined with a good display.

What Is a LUT?

The Flaws of Using Delta E Alone for Display Calibration
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RE: HOW TO - Set up madVR for Kodi DSPlayer & External Players - by Warner306 - 2016-04-14, 23:34
no image doubling tap - by oxynaz - 2016-12-13, 13:44
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