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Light color and spectrum analysis Apr 10, 2018

The color of the lights in the performing arts of the stage is extremely colorful. Some lighting engineers use large white light to illuminate the stage scenery. The original method is original and very interesting; some lighting engineers like to use color light, large-area dyeing, small pieces of spot color, and especially shake the audience's eyeballs. .

The color of the stage lighting mainly comes from two ways: the light color of the electro-optical source and the light color caused by the additional filter of the electric light source (or lamp).

1. Light color and spectral analysis of electric light source

Various types of electric light sources in the stage lighting are set to be bright and colorful, and their colors are unified with the corresponding color temperature or correlated color temperature. The radiation temperature of the black body quantitatively expresses the light color of the light source scientifically and represents the physiology digitally. Upper and psychological vision is a big step forward. Figure 1 is the published curve of the relative energy of spectral radiation for black bodies at various radiation temperatures. The interpretation of the map shows that:

1. The radiation temperature of black body (thermal radiation source) is different, and the relative energy of its spectral radiation is also different. The higher the temperature, the greater the relative energy of total radiation.

2. The spectrum of the temperature at each temperature is relatively continuous and uninterrupted.

3. When the temperature is different, the relative energy of the spectral radiation is released, and the ratio of the radiant energy in the red and blue bands is also different. The lower the radiation temperature, the greater the ratio of the red and blue radiation energy, the more warm and reddish the light color, and the lower the color temperature recorded as the light source; the higher the radiation temperature, the greater the ratio of the blue and red radiation energy. The light color is more white and blue, and the color temperature recorded as a light source is high. The two-color color temperature meter is based on this optical principle.

There are two major types of electric light sources for stage lighting: heat radiation sources and gas discharge light sources. Among the categories of heat radiation sources are: tungsten halogen lamps (halogen lamps), steamed aluminum bubbles, incandescent lamps, and the like, which are classified as gas discharge lamps: xenon lamps, metal halide lamps, and fluorescent lamps. They have their own relative energy distributions of spectral radiation. After stimulating the human eye, they often exhibit different light color effects. However, there is also the phenomenon of “halochrome”, that is, the light emitted by different spectral relative energies will also cause the same color vision, or the same light color may also have different spectral relative energy distribution.

The spectral relative energy distribution of a fluorescent lamp (3200K) and halogen tungsten foam (3200K), and the relative energy distribution of a fluorescent lamp (5500K) and sunlight (5500K). Reading these four lines can lead to insights as follows:

1. Different apertures have different spectral relative energy distributions, showing different light colors, each labeled with a different color temperature of 3200KT 5500K.

2. Objective metastasis exists objectively. Both light sources have the same color temperature, but their spectral relative energy distributions are not exactly the same.

3. The ratio of the relative energy of blue and red light in the spectral distribution of the color temperature 3200K light source is small, and the ratio of the relative energy of blue and red light in the spectral distribution of the color temperature 5500K light source is greatly improved.

4. The spectral relative energy distribution curve of tungsten halogen lamp and daylight is continuous, and it is a smooth transition. However, the spectral relative energy distribution curve of fluorescent lamps has several peaks, and several lines of intense radiation are sandwiched between them. These are several types of Phosphor chemical element feature line.

Although the energy distribution curve of the fluorescent light and the corresponding tungsten halogen lamp or sunlight is similar to the spectral distribution, the details of the spectral distribution are still different, and there are still some differences in the band. Although they are marked with the same color temperature of 3200K or 5500K, the difference between them is still implicit:

(1) Tungsten halogen lamps, the sun and the blackbody are all thermal radiation sources. Their chromaticity points are on the black body locus of the chromaticity diagram. Fluorescent lamps are different from the black body and are gas discharge lamps. Their chromaticity points deviate. The black body trajectory line only indicates that it is closest to the 3200K or 5500K chromaticity point and is marked with the color temperature of 3200K or 5500K. In order to distinguish this difference between the two, the color of the gas discharge light source is crowned with "correlated color temperature."

(2) Thermal radiation sources labeled with the same color temperature do not have the same color rendering properties as gas discharge sources. Since fluorescent lamps have significant line spectral distribution characteristics, they generally have a color rendering index lower than that of the same color temperature thermal radiation source.

The spectral relative energy distribution diagram of a xenon lamp (a kind of metal halide lamp) shows that the entire spectrum range is composed of several continuous spectrum spectra with strong spectral radiation, and the relative proportions of blue and red light. Higher. The color temperature of the deuterium lamp is between 5000K-600K. Its spectral distribution is similar to that of daylight, but its color rendering is less than that of daylight. Its color rendering index is between 80-90. It is a gas discharge lamp with high color temperature, high color rendering, and high luminous efficacy. It is completely satisfied with the technical requirements in the field of stage and film and television lighting, and it shows more and more broad application prospects.

Xenon lamp spectral relative energy distribution curve, its spectral distribution is very close to the daylight, the entire spectral range is a continuous spectrum, only about 480nm wavelet peak, with a stronger radiation energy. It is not difficult to infer that: Xenon lamp is also a high color temperature electric light source, color temperature is about 5500K, with excellent color rendering performance, its color rendering index can be as high as 94. The outstanding comprehensive performance of the xenon lamp is outstanding in the gas discharge lamp. Its development and application in high-luminosity long-range follow-up lamps, projection lamps, and spotlights have already yielded results.

When the stage lighting is gradually dimming and dimming, the light color and color temperature of the light source will change accordingly, indicating that the relative energy distribution of the spectral radiation changes. For example, when a halogen lamp is dimmed from a rated voltage value, the light parameter changes as follows: the light brightness and the color temperature gradually decrease, and the light color gradually shifts toward the red direction; conversely, when the working voltage is boosted, the brightness and the color temperature increase. The light color changes from a red fold to a yellow-white gradient. When using a dimming or non-rated voltage working condition in the case of a light sheet with a pre-light configuration, the general trend of changes in the color temperature of the light source to cause the change in the light color must be considered.

2. Shade and its spectral analysis

The color of the light may be converted, the simplest and most practical. The most common method is to configure a special color filter in front of the light source (or luminaire) to obtain a new light color.

There are two major categories of color filters: color temperature conversion filters (or color temperature than positive filters) and color light filters. The color filter has optical characteristics that selectively absorb light. For example, the color filter medium absorbs light of different wavelengths in the visible spectrum and changes the relative energy distribution of the light source. The transmitted light stimulates the human eye to induce Different from the light color effect of the light source. Different color filters have their own spectral transmittance curves, which convey their different selectively absorbed optical properties.