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Special report

LED lighting fixtures knowledge

作者: 来源: 更新日期: 2013/1/13

★ The reliable cooling system is the critical for protection of LED lighting fixtures stable continuous working.
The electricity energy is converted to light energy efficiency of 30% when LED is lightened, the rest all outputs in the form of heat. Without the reliable cooling system, the lifetime of LED will be reduced by half, and the light output will be reduced by approximately 10 percent as the junction temperature growing up every 10 degree. The light decay can be reached 50% for the lighting fixture which is used only 3000 hours. 

★The brightness testing as the lamps keep working for 1 hour is more credible.
The working temperature has to be rises as the lamps working. Some manufacturers reduce LED power to avoid a further increase in temperature. It leads to the brightness decrease a lot compared with the beginning of lighten, even decrease to 50%. The lamp with a good cooling system can maintain the reduction of only 0.1%.

A high general color rendering index is not entirely means of a perfect lighting color rendering.
1: What is the color rendering index – usually it is a kind of assessment of human eyes color distortion as the lamp illuminating on the objects. It can be divided into general color rendering index and special color rendering index of two categories.
2: Ra is the symbol of the most commonly used general color rendering index. The CIE (Commission of International Illumination) states its evaluation method: the eight sample color contrast under the testing light source and the referenced light source, these eight colors are medium chroma and lightness Munsell color scale:

The corresponding color rendering index is from R1to R8, Ra is the average value of these eight values. However the eight kinds of indicators are excluding human skin and dark lines.
★For studio, film and television industry, R13 and R15 should be paid particular attention for these special colors rendering index.
The general color rendering index is lack of assessment of human skin and dark lines, its assessment for LED lamps color rendering assessment is certainly one-sided view, so the special color rendering index comes in. CIE supplement the six kinds of color control patch for calculation of the special color rendering index, they are higher saturation of red, yellow, green, blue, skin color of European women and leaf green, China has also increased the complexion of seven kinds of samples including the skin color of Chinese women.

The corresponding color rendering index is from R9 to R15.
2: The film and television industry should pay more attention to the value of R13 and R15, even if the general rendering index can be reached 85 but if its index is low, it can also cause distortion of the human skin to be irradiated.

The method of shooting different lamps irradiation effect by camera in CCTV for color rendering index evaluation is worthy of learning.
A special color rendering index contras testing was held in CCTV new site on the afternoon of November 25, 2011.
The shortlisted six companies went to the final testing which should compliance with the requirement of high performance and high color rendering index by CCTV.
The method is based on the internationally accepted color card photos samples (three color zoom Avatar of European women, Asian women and African women), respectively, using halogen lamps and LED lamps produced by the six companies respectively shooting and recording by the HD camera monitor, and repeatedly contrast the differences of skin color. Five of the six companies’ products have different degrees of bluish or yellowish color distortion; only one product manufactured by Starlighting was totally agreed and judged almost no any distortion evaluated by the summit leaders, the experts and the six company representatives. Its general color rendering index Ra is 88, the R13 is 88, the R15 is 86. The attached drawing shows the photometric test report.

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