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Measurement and units |
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| Date: 2012-03-21 |
Professional lighting and fundamental unit of measurement
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Professional lighting and the four basic units of measurement
| Quantity |
Symbol |
Unit |
| Beam (flux) |
?/TD>
| Lumen |
| Luminosity |
I |
Candlelight |
| Illumination |
E |
Lux |
| Brightness |
L |
The brightness per unit area(cd/m2) |
Measurement and the relationship between the lighting unit:
Flux (f) and brightness (I) the relationship between the
brightness (I) and illumination (E) the relationship between the
injection angle cosine law of Cosine Law and vertical illuminance
Ming will use two different measurement parameters:
When electromagnetic radiation known lighting considerations, we will focus on the one hand, energy efficiency and other visual sensitivity of the eye; Basically, this is the perspective of two very different considerations, in the light quantification process is completely different data. To address this concern, usually works in accordance with clear examples of the most desirable solution to depend on: that is, the product of power consumption and eye visual acuity, therefore, just the human eye visual acuity measurement under the basis of projected light.
Light wattage:
Visual sensitivity of the eyes will change with the wavelength of light; in bright daylight environment, the eyes on the wavelength of yellow-green light (555 nm) the most sensitive; thus, at a wavelength of 555 nm under a power of energy (watts) into light energy (wattage), at different wavelengths of visible light energy of one watt, daytime eyes with visual acuity will be the spectral changes of various factors, such as daytime visual curve curve V (l); this way, light The wattage depends on the wavelength of light, for example: a wavelength of 490 nm wavelength of 555 nm alone, located in the visual eye sensitivity curve of day 20% of the position, and a wavelength of 490 nm light can only be a power energy ( w) conversion of light energy equivalent of 0.2 (wattage).
In the low brightness level, the visual eye sensitivity curve left (the equivalent of close to the shorter wavelength) and the high point of its most sensitive position is 507 nm, the curve is known as night vision sensitivity curve.
Candles:
Wattage of light is the perception of visible light into quantifiable units, side by side, in addition to a number of factors can be simulated two. However, although the wattage of light was once optical standards and follow the formula, also derived therefrom, the light unit - originally called "candle source candle power", Zhihou in 1948 was referred to as "candle candela", then they is in line with the direction of the real characteristics of the brightness of the unit; have a candle brightness of light per second to the amount projected in all directions is called "lumens lumen", a basic standard has continued to use so far.
The spectral efficiency of the best light
By calculation, we can see in the 555nm wavelength of energy under a power (in watts) is equivalent to 683 lumens, which is "the highest spectral efficiency light source," such as the wavelength of 490nm under a power of energy (Watts) is equivalent to 137 lumens (0.2x683 = 137lumens). Therefore, the lumen can be defined as under the eyes and visual sensitivity of the light source per second aggregate amount issued. | |
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