CIE 1931 Color Space

To understand color gamut, we first need to grasp the concept of the CIE 1931 color space.

We know that light is a wave, and the human eye (specifically the cone cells in the retina) is the organ that receives these waves. Cone cells cannot perceive all wavelengths of light; they can only detect light in the wavelength range of 380-780 nanometers. Therefore, light within this range is referred to as visible light. Light with wavelengths shorter than 380 nm is called ultraviolet, while light with wavelengths longer than 780 nm is called infrared.

Both ultraviolet and infrared light are invisible to the human eye. When we map the brightness and chromaticity of all visible light onto a plane, we obtain the CIE xy chromaticity diagram, which represents all the colors that the human eye can perceive. This range of colors is known as the CIE 1931 color space.

CIE 1931 color space

What is Color Gamut of a Screen?

Most colors can be synthesized by combining red, green, and blue in different proportions. Based on this principle, screens mix colors using their red, green, and blue subpixels to produce various colors.

Thus, the limit of a screen's ability to show colors is when the brightness of red, green, and blue is maximized. Other colors, created by mixing red, green, and blue, can only fall within the area defined by the triangle formed by the three points representing maximum brightness of each color. This triangle in the CIE xy chromaticity diagram represents all the colors the screen can reproduce, officially termed the screen's color gamut. The range of colors displayed by a screen is always smaller than the CIE 1931 color space (which represents all the colors visible to the human eye).

Color gamuts

In simple terms, color gamut indicates the richness of colors a screen can show: the wider the color gamut, the richer the colors; the narrower the color gamut, the more limited the colors.

What are Color Gamut Standards?

The range of colors that each screen can show varies, and different photographic devices and systems store different color information. To standardize, various industries have established different color standards, marking specific areas on the CIE 1931 chromaticity diagram as benchmarks for storing and displaying color information. These areas represents the color gamut standards. Common color gamut standards include sRGB, Adobe RGB, DCI-P3, NTSC, EBU and BT.2020.

Which Color Gamut Should I Choose?

When choosing a screen, how should we select the color gamut? Firstly, it's necessary to understand what the numbers in labels like "100% sRGB" mean: If a screen is 100% sRGB, it means it can reproduce all colors in the sRGB color gamut. A screen with 95% DCI-P3 indicates that it can reproduce 95% of the DCI-P3 color gamut. While 100% seems greater than 95%, in reality, the 95% DCI-P3 color gamut is much larger than 100% sRGB, approximately equating to 135% sRGB. Next, let's explore the application areas of different color gamut standards:

sRGB:
Commonly used for computers and is quite basic. The current Windows operating system uses 100% sRGB color space as a benchmark for storing color information. sRGB is one of the earliest and most universal standard color gamuts. Screens achieving 100% sRGB are considered mainstream general-purpose screens. Generally, when purchasing a computer screen, 100% sRGB is the best choice.

Adobe RGB:
Primarily used in photography, graphic design, and printing; it can be seen as an upgraded version of the sRGB color gamut.

DCI-P3:
Mainly used for audio-visual and gaming applications. It was developed to match the full range of colors that can be exhibited in movie scenes, focusing on visual impact rather than color completeness. RGBs LED screen products have a color gamut coverage of up to 99% DCI-P3. LED has an inherent advantage in color gamut, both OLED and LED offer a wider color gamut coverage compared to LCD or other display panels.

NTSC:
Mostly used in television. It is often employed to test the color range that TV screens can cover and is mainly used in the television industry. Aside from television content, it is rarely used as a standard for creation or color calibration.

Is a Wider Color Gamut Always Better?

As we have learned, a wider color gamut means a richer display of colors. So, when choosing a screen, is a wider color gamut always preferable?

Actually, a wider color gamut is not always better. For example, the Windows 10 operating system uses a 100% sRGB color space as a benchmark for storing color information. If a computer is equipped with Windows 10 and a screen with a 95% DCI-P3 color gamut, and it attempts to show pure blue (100% blue), Windows 10 will output the "bluest" information. The screen will then show the "bluest" available within its capability (95% DCI-P3, equivalent to 135% sRGB), rather than the 100% sRGB blue that Windows intended. This can result in an overly saturated image. Conversely, if the screen's gamut is less than 100% sRGB, such as 60% sRGB, the screen would show only the 60% sRGB color, leading to a less vivid, under-saturated image. So, when purchasing a screen for a computer configured with the Windows 10 operating system, a screen with 100% sRGB color gamut is generally the best choice.

However, over-saturation is not always a negative. Under-saturation can lead to dull colors, while over-saturation can make colors appear overly vibrant. If you are purchasing a computer for gaming, a higher saturation may be more appealing, and thus a wider color gamut screen could be a better choice.

As screen resolutions continue to increase, and the range of colors displayed becomes richer, to faithfully reproduce the colors we see with our eyes, and represent precious moments in their truest colors, are our pursuit of display quality. With advancements in technology, we believe we will increasingly be able to capture the truest beauty.