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Lumen scale3/12/2023 ![]() Light A is brighter because it has the higher effective lumen output. Once you turn both lights on, however, Light A would be twice as bright as Light B. If you were basing your decision solely on raw lumens, Light B would be the clear choice. LED Light B has an output rating of 3,000 raw lumens, but only 500 effective lumens. LED Light A has an output rating of 2,000 raw lumens and 1,000 effective lumens. To illustrate this point, let’s take a look at a practical example. This makes it very difficult to make an apples-to-apples comparison between lights and often results in consumers receiving less useable light than what’s advertised to them. Because of the cost and expertise involved in conducting photometric testing, some manufacturers opt to simply use the theoretical raw lumen numbers. Measuring the effective lumen output of a light requires the use of high-tech photometry equipment. The effective lumen output is an actual measurement of light output that does take into account all of the real-world losses we’ve just discussed. Now that we’ve covered why raw lumens are a theoretical measure that fails to account for real-world losses, let’s talk about effective lumens. How much less? That will depend upon the thermal management of the light, but the loss is typically in the neighborhood of 10 to 25 percent. We guess that most of you reading this article probably use your lights longer than 25 milliseconds at a time.which means that your light output is going to be less than the raw lumen value. Remember how the raw lumen calculation relies on the maximum output rating of the component LEDs? Some LED manufacturers calculate maximum output ratings by measuring the light output of the component LED after 25 milliseconds (equivalent in duration to the burst of a flash bulb). So, it stands to reason that if you measure the light output of an LED when you initially light it up (when it is cooler) verus after it has been on for 30 minutes (when it is hot), you’re going to see a decrease in the light output. In fact, it is not uncommon for LEDs to reach temperatures of over 212-degrees F (100-degrees C). And, as LEDs are powered for longer and longer periods of time, they typically heat up. LEDs produce less light the hotter they get. What causes these decreases in light output? Well, there are a couple of major contributing factors.
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