Light Output Measurements: Difference between revisions

While lumens measure the total output of a light, lux measures the amount of light that strikes a point on a wall. 1 lux is equal to 1 lumen per square meter. This can be measured with a light meter. The problem is that the value will go down as the light is moved further from the wall. Also the value will vary depending on whether the reading is taken in the hotspot or spill of the flashlight beam. Still, it is an easy measurement to make and many flashlight reviewers will use it. It can also be used pretty accurately to get a profile of how the brightness of a light varies with time. Reviewers can take an initial reading, call that 100%, and then chart how the light intensity varies until the battery is drained. See [http://en.wikipedia.org/wiki/Lux Wikipedia article] for more information on lux. 0.25 lux is said to be roughly equal to the light of a full moon. On Mythbusters, they determined you needed about 4 lux to navigate a room if your eyes aren't adjusted to the darkness. They also said that 300 lux is needed to read by.