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CIE diagram

The CIE diagram (International Commission on Illumination) is a graphical representation used to represent colors in various color models. It is widely used in lighting technology, the printing industry, and color science to describe and analyze color. The CIE diagram helps visualize color relationships and compare different light sources based on their color characteristics, such as color temperature and color rendering .

Basic information about the CIE diagram:

  1. CIE 1931 Color Space : The CIE 1931 XYZ color model forms the basis of the CIE diagram. This model was developed by the CIE and is based on the human eye's perception of color. The diagram shows the chromaticity of colors, meaning that it represents the saturation and hue of colors without taking brightness into account.

    • X, Y, Z are the three coordinates that define the color in this model.
    • The X and Y axes represent the ratio of the primary colors (red, green, blue).
    • The Z axis is often ignored in the diagram because the Y value is usually used to determine the brightness of the color.

  2. Chromaticity : The chromaticity of a color is determined by its position in the diagram. All colors within the diagram can be shown by coordinates (X, Y). Color values are represented by their x- and y-values , which refer to the saturation and hue.

  3. Visible color spectrum : The curve along the outer edge of the CIE diagram is called the "spectral locus." This represents the colors of the visible spectrum of light (the rainbow colors). These are the pure colors of visible light (such as red, green, and blue), and each color has its own unique location on the diagram.

  4. White point : The white point in the diagram represents neutral white light . In the CIE diagram this is indicated by the coordinates (x = 0.33, y = 0.33) . This point is important because the color temperature of light sources is often compared to the white point, especially when selecting lighting.

Key components of the CIE diagram:

  1. Color coordinates : Colors are positioned in the diagram by their chromaticity. This means you can see how a specific color relates to other colors by its placement in the diagram.

  2. Color temperature (Kelvin) : Color temperature can be represented on the diagram using a so-called "black-body line" or Planck curve . This represents the temperature of light sources such as the sun, candles, or LED lighting. The higher the temperature, the cooler and bluer the light, while lower temperatures are warmer and redder.

  3. RGB space : The RGB (red, green, blue) color models come from the CIE diagram, but RGB is more focused on digital displays and devices, while CIE is more focused on the perception of color by the human eye.

  4. Gamut : The gamut (range of colors) of a light source can be measured by looking at the area on the CIE diagram that the source's colors cover. This indicates whether the source is capable of displaying all colors, or whether it only offers a subset of colors.

Applications of the CIE diagram:

  1. Color Science and Perception : The CIE diagram helps scientists and designers understand how colors are perceived by the human eye.

  2. Lighting and LED Technology : In lighting, the diagram is used to determine how well a light source can realize color rendering (for example by comparing the color temperature and chromaticity of different LEDs).

  3. Color management in the printing and graphics industry : The CIE chart is used to standardize colors in printing processes, so that colors can be reproduced consistently and accurately.

  4. Screen Calibration : The diagram is used to understand how to correct colors on screens so that they are accurate and the colors are displayed correctly.

Summary:

The CIE chart is a graphical tool that shows the chromaticity of colors, based on the human eye's perception. It is widely used in lighting technology, color science, and the printing industry to analyze and compare the color rendering of light sources and display devices. The chart provides a visual aid for understanding color temperature, saturation, hue, and other color characteristics.