Analysis of Candlepower, Lumens, LUX and Foot Candles
   - www.magnalight.com

LUX is a measurement of illumination at distance.  In the chart above, an Extech light meter is used to measure the illumination at various distances from the light source, including 25 feet, 50 feet, 75 feet and 100 feet.  LUX represents the amount of useful light that enables you to see something at that distance.  For example, if I took a book and walked out 100 feet, how much light would I have to read by.  For example, I could read a book at 100 feet from most of the lights except the 1 watt led flashlight and the Mag Lite flashlight.  There is simply not enough light to see by at 100 feet.  The Golight 2049, for example will become difficult to use at 700+ feet, while the Golight 3049 will become useless beyond 850 feet.  The HML-5M-RC will become ineffective beyond 5000 feet, while the RL-10 will no longer give you enough light to read by 3000 feet. 

Type HID HID HID HID HID HID Halogen Halogen Halogen Halogen Halogen LED
Model AEX-25 PL-24 990X RL-11 5M-RC HL-15 GL-7901 GL-3049 RUL-9 GL-8130 Mag Lite 1W LED
Watts 25 24 35 35 35   65 65   65   1
100 feet 140 97 460 203 1259 345 190 140 63 192 14 3
75 feet 252 164 739 454 1582 627 233 266 102 305 31 5
50 feet 449 387 1668 1183 2237 1007 537 515 182 660 54 13
25 feet 1800 1358 2633 2352 3257 2645 2194 2190 1059 2230 281 55

As you can see in this comparison, the HML-5M-RC remote controlled spotlight projects 1000 LUX more of light on to an object at 100 feet than the Golight 2049 or Golight 3049 models.  Another important aspect to light is the ability for the beam to continue illuminating an object at distance.  Many lights project a strong beam up close, but taper off rather quickly.  This could be due to configuration of the bulb placement, reflector shape and size, color and coating of the reflector, etc.  LUX is an easily measured result that tells us whether a light will illuminate objects at distance.   

While candlepower and lumens are more popular measures of light output, neither really capture the actual useful light at distance.  There are no commonly available instruments to measure either candlepower or lumens.  Instead, formulas are used to estimate the “power” emitted by the light at the source of the light.  The formulas can include size of reflector, bulb wattage, mounting position, shape of the reflector, etc.  Formulas are specific to manufacturers and there are no universal standards.  While an inch or meter is the same any where in the world, one company’s candlepower formula can be dramatically different from another company’s formula.  Thus, some lights with multi-million candlepower may under-perform another company’s light with sub-million candlepower rating.  Lumens have taken the place of candlepower for HID and LED light sources and are calculated using proprietary formulas as well.  There are a few labs in the world (GE has one) that claim to possess the spherical chamber and instruments necessary to effectively capture and measure lumens.  However, in most cases, the manufacturers of the lights rely on the manufacturers of the lamp assemblies to specify lumen output. 

HID light and LED lights are commonly measured in lumens, while halogen lights are measured in candlepower, mostly due to tradition and competitive practices.  Neither lumens nor candlepower are an effective in determining just how much light will illuminate an object at distance.  LUX (or foot candles) is the only effective, easy to measure rating for this.  While candlepower and lumens are indicative of illumination at distance, there are many factors that influence the projection of a beam.  A poor quality reflector, for example, could impair a high lumen output bulb at distance.  The type of light source could also effect the projection of a beam.  The type and quality of the lens can have a dramatic impact on the illumination at distance.

LED lights, for example, rarely project well.  Current flows through phosphor covered plastic, causing the phosphor to glow.  Unless the LED light output is very carefully focused, an extremely bright LED simply won’t project illumination very far.  You simply can’t pump enough voltage into them to create illumination at distance.  LEDs, however, can have extremely high lumen output.  This is why they are extremely effective within beacons and light bars.  They can be seen glowing and flashing from great distances.  However, the light emitted from that same beacon cannot be used to read a book that is just a few feet away.   LEDs are an excellent example of how lumens and/or candlepower are not indicative of illumination at distance.

At www.magnalight.com we are familiar with all the measurement systems, depending on the type of light.  Given our experience, we feel pretty comfortable in creating comparative estimates.  We call this adjusted retail candlepower.  Based on our measurement of LUX at distance of all the lights we make and sell, we have a methodology for translating lumens to candlepower based on the LUX readings.  It is an attempt to create apples to apples comparisons of the various lights, irrespective of source lamp type and other factors.   

See www.magnalight.com or contact 800-369-6671 for more information.

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