Standard requirements for light sources in color light boxes1

The standard light source color light box is currently used in many industries. The main function of the standard light source color light box is the color matching and calibration of the appearance of the product. Many products have higher requirements on appearance and color, and some even directly affect the color. Due to the market sales of the product, the manufacturer must strictly control the appearance and color of the product, and the effect of the standard light source on the color light box is naturally highlighted. Therefore, the international statistical standards have made a series of requirements for the light source of the standard light source in the color light box. This article will focus on the requirements for marking the light source in the color matching phase. 1. Spectral requirements of the light source According to the requirements of ISO3664:2000, ordinary fluorescent tubes cannot be used as light sources for color observation, and special fluorescent tubes that meet the following technical requirements must be used: (1) The color temperature of the light source must be 5000K or 6500K, that is, observing the color under this light source color temperature is basically similar to the effect of observing the color under natural light from 8:00 am to 10:00 am and 3:00 pm to 5:00 pm in most parts of China. (2) The color rendering index Ra of the light source>90, that is, under this light source, more than 90% of the colors can be correctly observed. Second, the brightness of the light source requires a certain amount of illumination to observe the color of the object. It can be imagined that nothing can be seen in a dark room. According to the requirements of ISO3664:2000: (1) The brightness of the light source shining on the surface of the observed object through reflection should reach 2000Lux (+/-500Lux). The brightness of the illuminated surface is within the range of 1mX1m, and the brightness of any point shall not be lower than 75% of the brightness of the center of the illuminated surface. m2) (3) The brightness of the display should reach>75cd/m2 3. Requirements for the softness of the light source It is impossible to collect the light source and evenly and softly illuminate the surface of the illuminated object only by relying on a few standard light source tubes. This means that the standard observation light source must have a scientifically designed ambient light system to ensure that the energy of the light emitted by the fluorescent tube is irradiated as uniformly as possible on the surface of the illuminated object, and there is no light glare or light. shadow. 4. Requirements for the environment around the light source Observing color requires not only a standard light source and suitable light source brightness, but also strict requirements for the environment around the light source: (1) Other lighting sources around the observation light source cannot directly or indirectly affect the light source. Look at the surface of the object. (2) Observe the wall panels around the light source, the top and bottom (including the observer's own clothes) cannot use other colors, only the reflectivity can be used<60% neutral grey. (3) When observing color transmission photos, there must be a frame with a width of more than 50mm around the photo, and the color of the frame must be black.>90% black. 5. Color rendering index (Ra) The color rendering index is used to measure the ratio between the color that can be seen under the illumination of natural light and the color that can be seen under the illumination of a certain light source, that is, Ra=in a certain light source Colors that can be seen under illumination÷Colors that can be seen under natural light. Ra represents the color rendering index of a light source. The closer Ra is to 100%, the smaller the difference between the color displayed under the illumination of the light source and the color displayed under natural light. Note: Color temperature and color rendering index are two different physical concepts. Color temperature only reflects the color of the artificial light source, warmer or cooler. The color rendering index reflects the kinds of colors that can be displayed under the illumination of a light source. High color temperature does not mean high color rendering index, and high color rendering index does not mean high color temperature. 6. Color temperature (K) The color temperature of the light source is defined by the burning temperature when the color displayed by the light source is consistent with the color displayed when an absolute black body is burned at high temperature, and its unit is the absolute temperature Kelvin (K) . The higher the K value, the more white-blue the displayed color; the lower the K value, the more yellow-red the displayed color. 5000K (D50) is a standard light source tube with a slightly warmer (yellow) color tone, which is widely used in advertising art and prepress fields. But according to ISO3664:2000, this light source is now also mandatory in printing and other color management processes. 6500K (D65) is a standard light source tube with a slightly cooler (bluish) color tone. In the past in European and American countries, this light source was used in the printing field. But according to ISO3664:2000, this light source is gradually being replaced by the D50 light source. But in China, D65 light source is still the standard light source tube commonly used in the printing field. More about standard color matching light box: http://www.dsdengxiang.com/