If you've ever tried to compare flashlights or lighting of any kind, you've probably been confronted with a bunch of confusing terms like lumen and lux that are supposed to describe how powerful a light is.We think? Well here they are explained in a single image.
The image you see here, posted yesterday by the folks at Urban Velo, explains everything you need to know about the common terms lumens, lux, and candela. They're thinking about these in terms of bicycle lights, but they're applicable to everything from flashlights to lightbulbs.
The difference between the units lumen and lux is that the lux takes into account the area over which the luminous flux is spread. A flux of 1000 lumens, concentrated into an area of one square metre, lights up that square metre with an illuminance of 1000 lux.
Lux is defined as a measure of luminous flux over a unit of area. 1 lux = 1 lumen per square meter. Basically, it's a measurement of how light intensity is distributed. Measurements are typically taken at the center of the beam.