There are so many different LED headlight conversion kits on the market; it’s hard to decide which one is the best. Most will specify the Lumen output on the packing; normally 4,000 Lumen, 5,000 Lumen, or 6,000 Lumen. Sometimes you’ll see some headlight bulbs marked with 8,000 Lumen, 10,000 Lumen or even 12,000 Lumen. But what is the true Lumen of a LED headlight bulb?
In order to find out what’s actually true, let’s understand Lumen first.
The lumen (symbol: lm) is the SI derived unit of luminous flux, a measure of the total quantity of visible light emitted by a source. We measure the lumen of a LED headlight kit within a device called an integrating sphere. A bulb is positioned in the sphere and the light given off by the bulb is scattered inside the integrating sphere and evenly distributed to 360 degrees. The total brightness amount of a source of light can be measured accurately since light could be captured from all angles in the sphere without any interference from other light sources.