Lux is defined as being the measure of light intensity, as perceived by the human eye. It is the measure of light at a given distance on a surface. Driving light manufacturers have pushed aside Lumens in favour of Lux (Lx) and are 2016 latest buzz word in the driving light arena. Lux distance data is definitely an important metric but is misleading if considered in isolation. A laser pointer could theoretically have a peak beam distance of 5km at 1 lux, but I think we would all agree that a pair of laser pointers will make for an awful driving light.
When driving light manufacturers to carry out photometric testing to obtain isolux data, the goniophotometer used to test this metric only measures the peak intensity at the centre of the entire beam, which is great, but what about the rest of the beam? If 5 different driving lights all have 1 lux at 500m, which one do you buy? To obtain remarkable isolux numbers it is simply a matter of focusing down the beam, but beam focusing comes at the expense of light coverage. The very best driving lights are the ones that strike the best possible balance between brightness (Lm) and beam throw (Lx). Some of the best of the best driving light manufacturers refuse to quote lux distance numbers on their flagship products because taken in isolation is misleading in particular when customer's are comparing Lux data between separate manufacturers. The best driving light isn't necessarily the one that achieves the longest beam throw. The best driving lights in our view are the ones that have a well-formed usable overall beam shape, and most importantly, the one which is best suited to the customer's application
More information can be found in our LED Light Bar Buyer's Guide