How Brightness is Measured
The power of a car engine is measured by horsepower - the more the better. The same can be said for reflective material, which is measured by candle power (cd/lux/mē). There is a clear relationship between retroreflective performance of a surface and the distance at which it can be seen. According to 3M data, the retroreflective performance level (candle power) of white clothing is 0.1 - 0.3 , a license plate's performance level is at 50 and typical retroreflective silver fabric has a performance level of 500.
As the following chart depicts, with increasing retroreflective performance, sight distance also increases, clearly demonstrating that reflective materials allow for optimal visibility during low light level conditions. However, not all reflective materials are the same, as there are reflective materials available that range from 65-600 candle power. Remember, the brighter the better.
Text and graph copyright of 3M