The color of stage lighting mainly comes from two sources: the color of the electro-optical source and the color of the light caused by the additional color filter of the electric light source (or lamp).
1. The color of the electric light source and its spectrum analysis
There are various types of electric light sources in stage lighting, which are bright and colorful. Their colors are uniformly crowned with corresponding color temperature or correlated color temperature. The use of black body radiation temperature to quantitatively and scientifically describe the color of the light source, and digitally describe the physiological and psychological visual quantity is a great progress.
There are two main types of electric light sources for stage lighting: thermal radiation light sources and gas discharge light sources. The thermal radiation light sources include: halogen tungsten lamps (halogen lamps), vaporized aluminum bulbs, incandescent lamps, etc., and the gas discharge lamps include: xenon lamps, metal halide lamps, fluorescent lamps, etc. They have different relative energy distributions of spectral radiation, and usually present different light color effects after stimulating the human eye. However, there is also the phenomenon of "same color, different spectrum", that is, light with different spectral relative energy releases will also cause the same color vision, or the same light color may also have different spectral relative energy distributions.
The relative energy distribution of the spectrum of a fluorescent lamp (3200K) and a halogen tungsten bulb (3200K), and the relative energy distribution of the spectrum of a fluorescent lamp (5500K) and sunlight (5500K). Interpreting these four spectral lines can lead to the following insights:
1. Different lights have different relative energy distributions of the spectrum, presenting different light colors, and are marked with different color temperatures 3200KT5500K.
2. The phenomenon of isochromatic heterochromaticity exists objectively. The two light sources have the same color temperature, but their relative energy distributions of the spectrum are not exactly the same.
3. The relative energy ratio of blue and red light in the spectrum distribution of the color temperature 3200K light source is small, while the relative energy ratio of blue and red light in the spectrum distribution of the color temperature 5500K light source is greatly improved.
4. The relative energy distribution curves of the spectrum of halogen lamps and sunlight are continuous and smoothly transitioned, while the relative energy distribution curve of the spectrum of fluorescent lamps has several peaks, sandwiched between several strongly radiated line spectra, which are the characteristic spectral lines of several phosphor chemical elements.
Although the spectrum of fluorescent lamps is similar to that of the corresponding halogen lamps or sunlight, and the trend of the energy distribution curve is roughly the same, there are still differences in the details of the spectrum distribution, and the differences in some bands are still very large. Although they are marked with the same color temperature of 3200K or 5500K, there are still hidden differences between the two:
(1) Halogen lamps, the sun and black bodies are all thermal radiation sources, and their chromaticity points are on the blackbody locus of the chromaticity diagram. Unlike black bodies, fluorescent lamps are gas discharge lamps, and their chromaticity points deviate from the blackbody locus line. It only indicates that they are closest to the chromaticity points of 3200K or 5500K, so they are marked with a color temperature of 3200K or 5500K. In order to distinguish the difference between the two, the color of the gas discharge light source is named "correlated color temperature".
(2) Thermal radiation light sources and gas discharge light sources with the same color temperature do not have the same color rendering properties. Since fluorescent lamps have significant linear spectrum distribution characteristics, their color rendering index is usually lower than that of thermal radiation light sources with the same color temperature.
The relative energy distribution curve of the spectrum of a dysprosium lamp (a metal halide lamp) shows that the entire spectrum range is composed of a continuous spectrum with several linear spectra with strong spectral radiation in between, and the relative proportion of blue and red light is relatively high. The color temperature of the dysprosium lamp is between 5000K-600K, and its spectral distribution is similar to that of daylight, but its color rendering is not as good as that of daylight, and its color rendering index is between 80-90. It is a gas discharge lamp with high color temperature, high color rendering, and high light efficiency, which fully meets the technical requirements of the stage and film and television lighting fields, and shows an increasingly broad application prospect.
The relative energy distribution curve of the spectrum of a xenon lamp shows that its spectral distribution is very close to that of daylight. The entire spectrum range is a continuous spectrum, with only a small peak around 480nm, and has stronger radiation energy. It is not difficult to infer from this that xenon lamps are also a high color temperature electric light source with a color temperature of about 5500K, excellent color rendering performance, and a color rendering index of up to 94. The excellent comprehensive performance of xenon lamps stands out among gas discharge lamps. Its research and development and application in high-brightness long-range chase lights, projection lamps, and floodlights have long been fruitful.
When the stage lights are dimmed gradually, the light color and color temperature of the light source will change accordingly, indicating that the relative energy distribution of its spectral radiation has changed. For example, when the halogen tungsten lamp is dimmed from the rated voltage value, the change law of the light parameters is: the brightness and color temperature gradually decrease, and the light color gradually drifts toward the red direction. On the contrary, when the working voltage is pushed up, the brightness and color temperature will increase, and the light color will gradually change from red to yellow-white. When the color filter is configured in front of the lamp, when dimming or non-rated voltage working state is used, the general trend of color light change caused by the change of light source color temperature should be considered.
2. Color light and its spectrum analysis
The color of light can be converted. The simplest, most practical and most commonly used method is to configure a special color filter in front of the light source (or lamp) to obtain a new light color.
There are two major types of color filters: color temperature conversion filters (or color temperature positive filters) and color light filters. Color filters have the optical property of selective absorption of light. For example, the color filter medium has different proportions of absorption of light of each wavelength in the visible spectrum, which changes the relative energy distribution of the spectrum of the light source. Its transmitted light stimulates the human eye and induces a light color effect different from that of the light source. Color filters of different chromaticity have their own different spectral transmittance curves, which convey their different optical properties of selective absorption.
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