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Introduction
The RGB colour model is an additive colour model that combines red, green, and blue light in various ways to reproduce a wide range of colours. The model’s name is derived from the first letters of the three additive primary colours, red, green, and blue. It is commonly found in electronic systems such as televisions and computers, but it has also been used in traditional photography.
Because the colour elements (such as phosphors or dyes) and their response to the individual R, G, and B levels vary from manufacturer to manufacturer, different devices detect or reproduce a given RGB value differently. Without colour management, an RGB value does not define the same colour across devices.
The RGB colour model is additive in the sense that the three light beams are added together, and their light spectra are added, wavelength for wavelength, to form the final color’s spectrum. This is essentially the inverse of the subtractive colour model, which applies to paints, inks, dyes, and other substances whose colour is determined by how they reflect the light in which we see them.
Because of their properties, these three colours produce white, in contrast to physical colours, such as dyes, which produce black when mixed. When all of the components’ intensities are the same, the result is a shade of grey that can be darker or lighter depending on the intensity.
When they differ, the resulting hue is a colourized hue that is more or less saturated depending on the difference between the strongest and weakest primary colours used.
Every secondary colour is the inverse of one of the primary colours. Cyan is complementary to red, magenta is complementary to green, and yellow is complementary to blue.
RGB is used in the graphic design space when choosing appropriate colour schemes in designs such as logo’s or other artwork.
Physical principles guiding the selection of red, green, and blue
Primary colours are stimuli that maximise the difference between the responses of human retina cone cells to different wavelengths of light. The brain can detect the difference in response, and this difference is the basis of our perception of orange.
The use of only the three primary colours is insufficient for reproducing all colours. Only colours defined by the chromaticities of the primaries within the colour triangle can be reproduced by additive mixing of non-negative amounts of those light colours.
Geometric representation
Colors are typically defined by three components, not only in the RGB model, but also in other colour models like CIELAB and Y’UV. An RGB triplet (r,g,b) represents the three-dimensional coordinate of the given colour point within the cube, its faces, or along its edges.
This method computes the colour similarity of two given RGB colours by calculating the distance between them.
RGB use cases:
Photography:
The first experiments with RGB in early color photography were made in 1861 by James Clerk Maxwell a Scottish scientist.
The additive RGB model and variants such as orange–green–violet were also used in the Autochrome Lumière color plates. Such methods lasted until about 1960 using the expensive and extremely complex tri-color Autotype process.
TV (Television):
Colour TV pioneer John Logie Baird demonstrated the world’s first RGB color transmission in 1928. The Columbia Broadcasting System (CBS) began an experimental RGB field-sequential color system in 1940. Images were scanned electrically, but the system still used a moving part: the transparent RGB color wheel rotating at above 1,200 rpm in synchronism with the vertical scan.
More recently, color wheels have been used in field- Sequential projection TV receivers based on the Texas Instruments monochrome DLP imager.
Computers:
IBM introduced a 16-color scheme (four bits) with the Color Graphics Adapter (CGA) for its first IBM PC in 1981 The first manufacturer of a truecolor graphics card for PCs (the TARGA) was Truevision in 1987.
RGB became popular in 1987, mainly due to the arrival of the Video Graphics Array (VGA) in 1987 . Later variants of VGA (made by various manufacturers under the informal name Super VGA) eventually added true-color.
Scanners:
A scanner is a device that optically scans images and converts them to digital images that can be stored on a computer. Flat, drum, and film scanners, among others, are available, and the majority of them support RGB colour.
They are the descendants of early telephotography input devices that could send consecutive scan lines over standard telephonic lines.
Because early colour film scanners used a halogen lamp and a three-color filter wheel, scanning a single colour image required three exposures. Non-heating light sources, such as colour LEDs, eventually supplanted the technology.
Colours utilised in web-page design
HTML 3.2 formally adopted the RGB colour model as an Internet standard paving the way for it to be used across websites. The web-safe color palette consists of the 216 (63) combinations of red, green, and blue where each color can take one of six values (in hexadecimal): #00, #33, #66, #99, #CC or #FF.
The perceived intensity on a standard 2.5 gamma CRT / LCD is only: 0%, 2%, 10%, 28%, 57%, 100%. This seems fine for splitting up 216 colors into a cube of dimension 6.6.
The syntax for this within CSS is as follows:
rgb(#,#,#)
where # equals the proportion of red, green, and blue respectively. This syntax can be used after such selectors as “background-color:” or (for text) “color:”.
Conclusion
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Citation(s) referenced in this page:
(2001). RGB color model [Online]. Wikipedia. Available at: en.wikipedia.org/wiki/RGB_color_model (Accessed: 10 June 2021).
László Németh, CC0, via Wikimedia Commons
SharkD at English WikipediaLater versions were uploaded by Jacobolus at en.wikipedia., Public domain, via Wikimedia Commons
SharkD, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons