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2024-12-13
As a photoelectric device, the color matching light box can simulate different standard artificial light sources to ensure that the product has a color matching environment close to natural light. Different brands and specifications of color matching light boxes have different types of light sources, but they are often equipped with several common light sources. This article introduces the types and functions of common light sources for color matching light boxes.
Standard light source types
1. A (INCA) light source
Light source A is a gas-filled spiral tungsten filament lamp with a color temperature of 2856K, which is a typical incandescent lamp and is mainly used for accent lighting in homes or shops.
A Light Source
2.D65 light source
Among the D series standard illuminants, CIE recommends D65 as the preferred illuminant. D65 represents the average daylight with a correlated color temperature of 6500K. It is an average result of measuring the daylight in the northern window of the northern hemisphere on a cloudy day regardless of the season and time of the day. In many standards such as ISO 105-A01 "General Rules for Testing Color Fastness of Textiles" and ASTM D1729 "Standard Method for Visual Evaluation of Opaque Materials", D65 is an indispensable standard light source. However, due to the special spectral power distribution of D65, there is currently no artificial light source that can emit light with the same spectral power distribution as D65, and it can only be approximately simulated. In most standard light boxes, two high color rendering fluorescent lamps are used to simulate the D65 light source, while in the GretagMacbeth SPLⅢ standard light box, tungsten filter technology is used to simulate the D65 light source with two tungsten halogen lamps.
D65 light source
3. Commercial customer light source (F series light source)
TL84 light source (F) belongs to the F series fluorescent light source, which is a unique product of Philips. It has become an important commercial color matching light source in the European market because it is widely used in Marks & Spencer in the UK. TL84 light source is generally realized by Philips' "TLD" type (thin tube diameter type) fluorescent tube coated with rare earth phosphor. It is a three-primary color fluorescent lamp with a correlated color temperature of 4000K.
CWF light source (F2) is mainly used in commercial and office institutions in the United States, and its correlated color temperature is 4150 K. CWF is the abbreviation of Cool White Fluoresent, which is a cold white fluorescent lamp.
U30/TL83 light source (F12): U30 stands for Ultralume 3000, which is also a tri-color fluorescent lamp with a correlated color temperature of 3000K. U30 lamps manufactured by Westinghouse are used in Sears department stores throughout the United States. U30 light source is equivalent to TL83 light source used in Europe. In GretagMacbeth Judge II standard light box, Philips TL83 fluorescent lamp is used to realize U30 light source.
TL84 Light Source
4. Other light sources
In addition to the above light sources, general light boxes are also equipped with UV light sources, which are ultraviolet lamps. They are often used alone or in combination with other light sources to check whether the fabric is whitened and contains fluorescent dyes. In addition, some light boxes are also equipped with HOR (HORIZON) light sources. This is a halogen tungsten lamp that simulates daylight in the morning or evening.
UV light source
The characteristics of a light source are determined by its relative spectral power distribution S (λ). The so-called relative spectral power distribution refers to the functional relationship between the relative value of spectral density and wavelength, that is, the relative energy ratio at different wavelengths in the light emitted by the light source. The following figure shows the relative spectral power distribution curves of several commonly used color light sources, with the horizontal axis being the wavelength and the vertical axis being the relative spectral power distribution.
1. Relative spectral power distribution curve of light source A
A light source relative spectral power distribution curve
2. Relative spectral power distribution curve of D65 light source
D65 light source relative spectral power distribution curve
3. Relative spectral power distribution curve of CWF light source
Relative spectral power distribution curve of CWF light source
4. TL84 light source relative spectral power distribution curve
Relative spectral power distribution curve of TL84 light source
5. TL83 light source relative spectral power distribution curve
Relative spectral power distribution curve of TL83 light source
The relative spectral power distribution curves of the five commonly used color light sources shown in Figures 1-5 above are different. Some are continuous spectra, some are discontinuous spectra, and some have only a few linear band spectra. A certain spectral power distribution is manifested as a certain light color. As can be seen from Figure 1, light source A has lower energy in the short-wave region and higher energy in the long-wave region, so the light color of light source A is reddish and yellowish; the high color rendering fluorescent lamp shown in Figure 2 uses multi-band phosphors, with a wider spectrum and a light color that tends to be white, but its relative spectral power distribution is still different from that of D65; the CWF in Figure 3 is an ordinary fluorescent lamp, which uses halophosphate phosphors, has a wider spectrum, and the peak of the spectral power distribution is around 580nm, and the light color is yellowish and greenish; although TL84 and TL83 (U30) in Figures 4 and 5 belong to the same three-primary color light source and have similar linear band spectrum distributions, their properties are very different due to the different wavelengths corresponding to the linear band spectra where the highest radiation energy is located. As a result, the light color of TL84 is blue while the light color of TL83 (U30) is yellowish.
The color of the light source directly affects the color of the object. The color of the object is the result of the object selectively absorbing the complementary color components in the incident light and reflecting the remaining color light. Different incident light spectra will produce different color effects.
Standard light source
1.A Light source function
When we use the standard, some models of product control panels often have light source A, which is a tungsten filament lamp with a color temperature of 2856K and a power of 60W. It is mainly used for metamerism detection. In the standard light source color matching light box, the light with the best color rendering performance is the incandescent lamp. Color matching light source A is an incandescent light source, so it is usually used as a colorimetric reference lamp. The main uses include simulating the light environment under window lighting conditions and evaluating metamerism effects.
2.D65 light source
This is the most commonly used artificial simulated daylight in China, with a color temperature of 6500K, the average natural daylight in the north, replacing natural light for color matching, and is suitable for general requirements. Most customers specify D65 for color matching to ensure that when observing the color effect of objects indoors or on rainy days, there is a lighting effect similar to that observed under sunlight. In simple terms, the D65 standard light source is an artificial light source that simulates daylight, and its spectral value conforms to the visual color standards of Europe and Pacific Rim countries.
3.TL84 light source
TL84 light source is also called F11 light source. This light source is a narrow-band white fluorescent lamp and is a common lighting method in European stores. For products sold or exported to Europe, color evaluation under this light source is usually required to ensure color accuracy and consistency. European and Japanese customers usually specify the use of TL84 light source for color matching because its higher color rendering index can provide better color reproduction.
4.CWF light source
CWF is short for Cool White Fluorescent, which is a cool white fluorescent light source with a color temperature of 4150K, which meets the CIE (International Commission on Illumination) standard illuminant F2. The color rendering index (CRI) of CWF light source is about 62, and it is characterized by emitting a lot of green light and less red light, so it is often selected by many American brands when matching colors. For products exported to the North American market, it is often necessary to conduct color evaluation and matching according to the conditions of this type of light source.
5.UV light source
UV light source is what we often call purple light, that is, ultraviolet light source. It is widely used. For example, the common banknote detector is a device made using the principle of ultraviolet light. The UV light source in the color light box is an ultraviolet lamp, which is often used alone or in combination with other light sources to check whether the fabric products are whitened and contain fluorescent dyes.
