1000 lux, per my tests, seem to be minimum lux for inspection. You need 4000 candela for 1000 lux for 2 meter viewing. Most work is a bounce between 1 meter and 2 meter:90%of time. A fact underlined when my optometrist ruined my 6 foot and under vision by forcing me into superman 20/8 contacts, from my 20/25 astigmatism. 90 percent of my eyesight ruined. It cost mr $2500 to fix. Anyway, Upper teen lux is too bright. Outside, working in shade, 700 to 7000 lux is typical. But I pull out headlamp when lux drops to 1000, half hour before dusk and heavily cloudy days on covered porches. Obviously, lux, candela, lumens, are all different things. The allowable runtime, allowable weight, top emitter efficiency, top driver efficiency, top battery energy density per weight/volume, lens antiflectivity, are all thing that are variables that are absolute. After those are calculated, you have xxx lumens to shape into some thing that can do the job required. If you had unlimited resource, lumens, there would never, ever be a need for any reflector or optic. The wise choice of beam shape optimizes how well you will see at your final allowance of lumens!!! The best quote is, " If you are looking for something or navigating, you want flood:if you are looking at something you want throw (1000lux)". One exception is you want throw looking for something in a messy area, especially if object has little contrast with surroundings. And you may want throw and peripheral, going down a mountain at 30 mph on a bike. Plastic reflectors I own, you can see light leaking through and I can measure a 20 percent drop in lumens, their lux can be good. Also, epoxy star electric areas, to water proof, cut holes/slots in bezel to open up bezel for chimney effect, and your aluminum reflector/inside of bezel works to release heat into the air, increasing led efficiency. I made water proof seal between reflector and star. I also abandoned the cylinder, went for a cpu styled, finned heat sink. Headlamp and wrist light.
On a personal note, I have had many headlamps, most failures. One headlamp, with too little runtime for a tasklight, due to mathematics of its greedy beam shape, had Hotspot as wide as my shoulders looking at my feet and Corona about 120 degrees. I realized this is a flood light for my standards, as it can illuminate both pages of a book, and covers my eye cones generously with the Hotspot and my rods with the Corona. In my lifetime, a floodier light would be a foolish waste of juice. Just a thought. Shoulder wide Hotspot, looking down from headlamp: maybe with jacket on, probably roughly (though not always) convertible through many body types of larger and smaller people with normal body proportions. Just a thought that seems empirical.
