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In the
In the film industry
The film industry or motion picture industry comprises the technological and commercial institutions of filmmaking, i.e., film production companies, film studios, cinematography, animation, film production, screenwriting, pre-production, post ...
, 3D lookup table
In computer science, a lookup table (LUT) is an array that replaces runtime computation with a simpler array indexing operation. The process is termed as "direct addressing" and LUTs differ from hash tables in a way that, to retrieve a value v wi ...
s (3D LUTs) are used to map one color space
A color space is a specific organization of colors. In combination with color profiling supported by various physical devices, it supports reproducible representations of colorwhether such representation entails an analog or a digital represent ...
to another. They are commonly used to calculate preview colors for a monitor or digital projector of how an image will be reproduced on another display device, typically the final digitally projected image or release print
A release print is a copy of a film that is provided to a movie theater for exhibition.
Definitions
Release prints are not to be confused with other types of prints used in the photochemical post-production process:
* Rush prints, or dailies, ...
of a movie. A 3D LUT is a 3D lattice of output RGB color values that can be indexed by sets of input RGB colour values. Each axis of the lattice represents one of the three input color components and the input color thus defines a point inside the lattice. Since the point may not be on a lattice point, the lattice values must be interpolated; most products use trilinear interpolation
Trilinear interpolation is a method of multivariate interpolation on a 3-dimensional regular grid. It approximates the value of a function at an intermediate point (x, y, z) within the local axial rectangular prism linearly, using function data on ...
.Selan, Jeremy (2004). "Using Lookup Tables to Accelerate Color Transformations" ''GPU Gems 2'', Chapter 24. https://developer.nvidia.com/gpugems/GPUGems2/gpugems2_chapter24.html
3D LUTs are used extensively in the movie production chain, as part of the Digital Intermediate
Digital intermediate (typically abbreviated DI) is a motion picture finishing process which classically involves digitizing a motion picture and manipulating the color and other image characteristics.
Definition and overview
A digital intermediate ...
process.
Cubes may be of various sizes and bit depths. Often 33×33×33 cubes are used as 3D LUTs. The most common practice is to use RGB
The RGB color model is an additive color model in which the red, green and blue primary colors of light are added together in various ways to reproduce a broad array of colors. The name of the model comes from the initials of the three addi ...
10-bit/component log images as the input to the 3D LUT. Output is usually RGB values that are to be placed unchanged into a display device's buffer.
Modern graphics cards have direct support for 3D LUTs, allowing entire HD images to be processed at 60 fps or faster.
See also
*Color grading
Color grading is a post-production process common to filmmaking and video editing of altering the appearance of an image for presentation in different environments on different devices. Various attributes of an image such as contrast, color, s ...
* Color calibration
The aim of color calibration is to measure and/or adjust the color response of a device (input or output) to a known state. In International Color Consortium (ICC) terms, this is the basis for an additional color characterization of the device ...
* Color management
In digital imaging systems, color management (or colour management) is the controlled conversion between the color representations of various devices, such as image scanners, digital cameras, monitors, TV screens, film printers, computer printer ...
References