With a light meter you can measure the lux value of any surface or space. A lamp that gives the same number of lux at three meters distance than a lamp measured at one meter is much more powerful than the one measured on a meter. Be careful when making a comparison between two lamps. Lux can be measured from different distances. The number of lux is thus found as the quotient of the total received luminous flux, expressed in lumens, and the size of the illuminated area expressed in square meters therefore 1 lux = 1 lumen / m². The lux thus corresponds to the illuminance that is obtained when each square meter of the considered surface receives a luminous flux of one lumen. The lux (symbol lx), latin for light, is a unit of illumination: 1 lux is the illuminance produced by 1 candela on a surface perpendicular to the light rays at a distance of 1 meter from the source. The smaller the angle of radiation in which the light is emitted, the higher the luminous intensity (with constant luminous flux). An incandescent lamp gives a luminous flux of approximately 12 lm / W. The luminous flux depends on the power of the source and on the color of the light. If one sees a part of a light beam, that part has a smaller luminous flux (in lumen) but (in principle) the same luminous intensity (in candela) as the whole beam. Light intensity is a measure of the light density. Luminous flux is a measure of the total amount of light in a light beam. Lumen is therefore the unit to measure the brightness of a light source independently of the direction of the light beam. Luminous flux takes into account the sensitivity of the eye to the visible part of the electromagnetic radiation. It measures the total amount of light emitted by a light source in all directions. For conversion, 1 foot-candle = 10.764 lux.The lumen (symbol: lm) is the unit for luminous flux. The difference is that the foot-candle uses the Imperial standard measuring system (feet, pounds, etc.), while the lux uses the metric system (meters, grams, etc.).Ī single foot-candle is equivalent to the amount of light that falls on a surface that is one foot away from a single candle, and a lux is the amount of light that falls on a surface one meter away from a candle. The current standard unit of measure to be used is “candela.”įoot-Candles & Lux Foot-candles and lux measure the same thing-the amount of visible light that falls on a surface. One candela is close to the light intensity produced by an ordinary candle as perceived by the human eye, and addresses how bright a light source is in a particular direction.Īlthough the term “candlepower” was once the predominant unit of measure used to describe the intensity of a light, this term is now considered to be obsolete. The key difference between the two is that candela is specifically a measurement of directional intensity. The Effective Lumen output is measured using a photometric testing device and takes into consideration electrical and optical losses, so it is a better representation of the useful visible light that is produced.Read more on how to calculate Effective Lumens here.Ĭandela are similar to lumens in that both deal with light output as perceived by the human eye. Effective Lumens: a measure of the total power output of a light source.In the case of LED lights, this figure is computed by multiplying the manufacturer’s lumen rating for the LED by the number of LEDs in the light.Raw Lumens are NOT representative of the actual light output because it does not take into account the electrical and optical losses that impact all lights. Raw Lumens: a measure of the theoretical output of a light.Speaker offers two types of lumens in our specification sheets: When you want to know how bright a light will be, you need to identify the lumen output, not the wattage-especially when comparing LED and bulb-based lights. Watts are a measure of power consumption, while lumens are a measurement of visible light output. LEDs can emit the same, if not more light than a bulb, while consuming less power. With LED technology, this is not the case. It is a common misconception that higher wattage equals higher light output-in part due to the fact that incandescent light output generally increases with wattage numbers. Foot-candles and lux: the amount of visible light falling on a surface.Candela: a measure of the intensity of a light source in a particular direction.Candlepower: an obsolete term that has been replaced by “candela”.Lumen: a measure of the total visible light output of a light source.Watt: a measure of the total power output of a light source. To help you stay informed and educated, here are some basic terms for understanding lighting technology. These technological advances have also led to an abundance of terminology. Thanks to advancements in lighting technology, we enjoy some of the brightest, longest-lasting, and most efficient lighting options the world has ever seen.
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