Color Gamut
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Color gamut refers to the range of colors that a display can reproduce. It is typically represented by the area of a triangle formed by the coordinates of the three primary colors (Red, Green, and Blue) on the CIE 1931 chromaticity diagram. This triangle’s area is compared to a reference area of standard primary colors to determine the gamut coverage. There are several standards for color gamuts, each established by different organizations. Below are some key standards and their calculation methods:
1. NTSC Standard:
• Definition: Established by the National Television Standards Committee (NTSC) in 1953.
• Calculation: The area of the triangle formed by the primary colors of the display sample is divided by the area of the standard NTSC primary colors. The result is expressed as a percentage.
• Example: If the area of the display sample’s primary color triangle is 0.085 and the standard NTSC triangle is 0.1, then the NTSC coverage is \frac{0.085}{0.1} \times 100\% = 85\% .
2. sRGB Standard:
• Definition: Developed by the International Electrical Commission (IEC) in 1996 for digital imaging, equivalent to the International Radio Consultative Committee’s (CCIR) HDTV studio standard from 1988.
• Calculation: The intersection area between the display sample’s primary color triangle and the sRGB triangle is divided by the area of the sRGB triangle. The result is expressed as a percentage.
• Example: If the intersection area is 0.07 and the sRGB triangle area is 0.08, the sRGB coverage is \frac{0.07}{0.08} \times 100\% = 87.5\% .
3. Adobe RGB Standard:
• Definition: Proposed by Adobe Systems in 1998, it has a broader color space than sRGB and is typically used in printing and image processing.
• Calculation: Similar to the sRGB standard, the intersection area between the display sample’s primary color triangle and the Adobe RGB triangle is divided by the area of the Adobe RGB triangle.
• Example: If the intersection area is 0.09 and the Adobe RGB triangle area is 0.1, the Adobe RGB coverage is \frac{0.09}{0.1} \times 100\% = 90\% .
4. BT.2020 Standard:
• Definition: Released by the International Telecommunication Union (ITU) in August 2012 for wide color gamut in broadcasting. It covers 133% of the NTSC gamut.
• Calculation: The area of the triangle formed by the primary colors of the display sample is divided by the area of the BT.2020 standard triangle. The result is expressed as a percentage.
• Example: If the display sample’s triangle area is 0.11 and the BT.2020 triangle area is 0.12, the BT.2020 coverage is \frac{0.11}{0.12} \times 100\% = 91.67\% .
5. DCI-P3 Standard:
• Definition: Developed by Digital Cinema Initiatives, LLC (DCI) in 2005 for digital cinema. It is used by major film studios like Disney, Fox, Paramount, Sony Pictures, Universal, and Warner Bros.
• Calculation: The intersection area between the display sample’s primary color triangle and the DCI-P3 triangle is divided by the area of the DCI-P3 triangle.
• Example: If the intersection area is 0.095 and the DCI-P3 triangle area is 0.1, the DCI-P3 coverage is \frac{0.095}{0.1} \times 100\% = 95\% .