Headlight LED conversion
https://store.candlepower.com/h7headlamps.html
Basically lumen is how much light a bulb is capable of producing while lux is how bright the bulb is actually.
With that said, there have been significant improvements with LED bulbs over the years. Early on the diodes used in LED bulbs were incompatible with incandescent reflector housings because they were not designed for LED light sources. The diodes were not able to focus light the same way that a filament was capable of doing. The headlight would appear bright but would be useless down the road. Now LED bulbs use diodes which focus the light in a much tighter tolerance, mimicking an incandescent filament much better than they used to be able. They're still not a direct replacement but are very close. This all depends on what you buy. Cheap alternatives from eBay will not be designed well, have crooked diodes, and even use no-name or knock-off diodes. Name brand options from brands like OSRAM or Philips are designed to be as closely compatible with incandescent reflector housings as possible since, well, they have the resources.
Despite improvements to LED bulbs or options from reputable brands, they are still not a good choice to use in projectors because projectors harness the light produced by a bulb differently. In a projector all of the light produced by a bulb is utilized whereas in a reflector typically only the sides of the bulb are utilized. Since LED bulbs are two sided, they perform poorly in a projector but fairly well in a reflector.








