Definition of Color Gamut

Color gamut refers to the range of all colors that a device (such as a monitor, printer, etc.) can reproduce. It reflects the device's capability in color representation, and different devices have varying color gamut ranges due to differences in technology and materials. Understanding color gamut is crucial for ensuring the accuracy of colors in images and videos, especially in fields like design, photography, and printing.

In the real world, the colors of the visible spectrum in nature form the largest color gamut space, which includes all the colors that the human eye can see.

To intuitively express the concept of color gamut, the CIE (International Commission on Illumination) has established a method for describing color gamut: the CIE-xy chromaticity diagram.

Representation of Color Gamut

CIE Chromaticity Diagram

The CIE (International Commission on Illumination) has developed the CIE-xy chromaticity diagram to visually represent color gamut. In this coordinate system, the range of colors that various display devices can represent is shown as a triangular area formed by connecting three points representing RGB (Red, Green, Blue). The size and shape of this area reflect the types of colors that the device can display.The larger the area, the greater the color gamut range of the device.

Color Gamut Standards

• sRGB: The most widely used standard, suitable for most computer and web applications, covering approximately 72% of the NTSC color gamut.The sRGB color gamut was born in 1996 and has been the most commonly used standard since the CRT(Cathode Ray Tube) era until now. Almost all monitors support sRGB nowadays, and it can easily handle web browsing, graphic work, daily office tasks, and more. Therefore, achieving 100% sRGB color gamut coverage is something that many better monitors can do now. However, the sRGB color space is only about one-third of the CIE 1931 XYZ color space, and sRGB has insufficient coverage for the green part of the color gamut. So, if an image originally has very rich greens (such as a picture of green leaves), it may lack expressiveness when viewed under sRGB. More importantly, sRGB is only suitable for self-luminous display screens to display "virtual" images and cannot be used on "physical" printed materials that rely on reflected light for color display. Therefore, to standardize the colors of printed materials, the CMYK color standard came into being.

• Adobe RGB: Launched by Adobe, it can express a broader range of greens and cyans, making it suitable for professional photography and design.The Adobe RGB color gamut was primarily developed to address the issue that the sRGB color gamut cannot cover the CMYK color gamut used in printing systems. Its main improvement is in the display of cyan-green tones, covering approximately 50% of the CIE 1931 XYZ color space. We can see their relationship in the color gamut diagram. Adobe RGB is a considerably large color gamut, and some high-end professional monitors used for photography and design can achieve 99% Adobe RGB color gamut coverage, offering very powerful performance.
• Rec.709 color standard is the international standard for high-definition television. In 1990, the International Telecommunication Union adopted Rec.709 as the unified color standard for HDTV. It has a relatively small color gamut and is the same as the sRGB color space used for internet media. Most films need to be transcoded based on the Rec.709 color standard during the post-release process to provide movie carriers that conform to mainstream playback forms such as online videos and Blu-ray DVDs. Movie videos are captured and produced in the DCI-P3 color space, but when converted to DVDs or sources that users can watch, they are uniformly converted to the Rec.709 color space.In fact, the color reproduction capability of a display device can be quantified, and it is intuitively reflected through the concept of color space, which is a three-dimensional area containing all possible colors. The horizontal and vertical directions are used to describe changes in saturation and brightness, respectively. In fact, every projector and computer monitor displays images by combining primary colors in different ratios and intensities. They respond to changes in these primary colors based on the range of colors that the available devices can produce. Since most display devices use three primary colors, their color spaces are displayed as triangles.Later, the International Telecommunication Union upgraded the Rec.709 standard to the BT.709 standard, but there was no change in color gamut. BT709 is an SDR color gamut, and a color gamut exceeding 100% BT709 is considered a wide-color-gamut TV.As can be seen from the above figure, the color gamut of Rec.709/BT.709 is the same size as that of sRGB. They are consistent in color gamut range, primary color coordinates, and white point, but the Gamma curve is different. That is to say, the brightness of Rec.709/BT.709 is slightly lower than that of sRGB.On some high-end monitors, both sRGB and Rec.709 color gamuts can be displayed simultaneously. This not only provides a better monitoring environment for film and television production but also can more accurately restore the colors of film and television works. The final effect after production and distribution allows us to have a more intuitive reference throughout the process.

• BT.2020 is an HDR color gamut, and currently, top-tier OLED TVs can cover about 80% of it. Rec.2020/BT.2020 is the color gamut standard for ultra-high-definition television signals, and current 4K TVs can display the BT.2020 color gamut.As can be seen from the color gamut chart, it adopts a wider color gamut space than BT.709, with a larger display range in orange and green, allowing for more abundant colors. It can achieve more delicate transitions in color levels for ultra-high-definition, 4K images. For BT.2020, professional film and television monitors can already support it well, but the support for the BT.2020 color gamut by regular displays still needs improvement.

• DCI-P3 color gamut is a color standard established by DCI, which specializes in setting digital cinema technical standards, quality standards, logistical standards, and legal standards, with color standards being just one aspect. Based on this historical background, the DCI-P3 color gamut is mainly applied in the field of digital film and television. It emphasizes visual impact and has a wider red/green color gamut than the traditional sRGB color gamut.As can be seen from the color gamut chart, DCI-P3 is not the standard with the widest color gamut. However, compared to Rec.709 and sRGB, it covers an additional 25%. Due to technological advancements, some high-end monitors can already meet this standard, providing a better viewing experience for video and playing a very important role in film and television production, especially. in movie production.

• NTSC is a color gamut standard established by the National Television System Committee of the United States, initially used to test the color coverage range of television screens. The NTSC color gamut holds an important position in the television industry but is relatively less applied in other creative or color correction fields. The NTSC color gamut has a wide coverage and is commonly used for comparison with other color gamuts. 100% of the sRGB color gamut is roughly equivalent to 72% of the NTSC color gamut, and this conversion is only applicable for comparing the coverage areas of color gamuts.

Importance of Color Gamut

1. Accuracy and Consistency: Color gamut directly affects the quality of images and videos. High-gamut displays can present richer and more vibrant colors, enhancing the visual experience.
2. Application Scenarios: In professional fields like design, photography, and printing, selecting appropriate devices to match the required color gamut standards is crucial to ensure that final outputs meet expected results.
3. Technological Advances: With advancements in technology, an increasing number of new displays support wider color gamuts, such as 4K ultra-high-definition displays, which can provide higher quality visual experiences.
4. Besides defining the range of colors that a device can reproduce, another major reason why color gamut is important is that for devices that depict colors, the color gamut serves as a shared language for every element in the ecosystem, from cameras to media players to display devices, to ensure that all colors used by a given device are synchronized with all other devices. Without a shared color gamut, it would be impossible to ensure that the specific color produced by a projector (such as a certain shade of purple) is the same as the purple transmitted by the media player. Therefore, the color gamut, as a reference point, defines every color used in the ecosystem, thereby generating replicated images.

Color Gamut and Workflow

In practical applications, understanding color gamut can help professionals make more informed choices. For example, when editing images, using software or devices that support a wider color gamut can ensure that final outputs maintain consistent colors across different devices. This is vital for brand image and customer satisfaction.

Welcome to contact us for more information.