Great shout out for Kelvins - thank you for that, a common term I hate seeing misunderstood!
Originally Posted by Macd7919
I'm going to add to that, because "Lumens" is a personal pet peeve - possibly the most abused and misunderstood LED marketing ploy.
This was the best explanation I have come across explaining the difference between "available" light (lumens) and "usable" light (lux):
Imagine a shot glass full of "10,000" drops of water. This is Lumens. You have 10,000 of them in the shot glass, and it is overflowing with awesome.
Now pour that shot glass into a kiddie pool. Same 10,000 Lumens, but your previously overflowing shot glass full of Lumens is now useless. This is Lux.
If you cannot focus and apply your available Lumens to the road (in this case), then your Lux will be crap regardless of how many millions of Lumens it claims to produce.
So a light source with a lot of Lumens sounds super sexy, but if you have a crap reflector and a crap lens then you get crap light, which is low Lux - i.e. most dime-a-dozen "Chinavision" AliExpress/eBay/Amazon LED headlight bulbs.