What’s in a lumen?

What does it mean when lighting companies talk about lumen? There are 3 different lumen outputs: theoretical, cold and effective (or measured).

The losses caused by the optical system and the heat effects of the LED chips are not deducted from the theoretical lumen output.

TYRI measures effective lumen output when a LED work light after 30 – 45 minutes has reached its operating temperature. The cold lumen output has decreased because all LED Chips have a lower efficiency when the temperature is higher. The lumen output is thus reduced by 5 % due to the heat. The losses due to the optical system are about 20 – 25 % which means that the effective lumen output is in total about 70 – 75 % of the theoretical lumen output.

If you measure low quality products the losses can be between 50 and 70 % in total. For instance: 3000 theoretical lumen gives about 900 to 1500 effective lumen. If nothing is indicated in the product data sheet you can assume that the theoretical lumen output is meant. So watch out!

Important to know: The effective lumen output in combination with the optical system creates the lux value. Light should therefore always be compared by Lux and not by lumen output. The better the optical system the more light on your working area.

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