I’m buying headlamps and batteries… I use them a great deal. It started with biking at night, and then I noticed how handy they were for so many things…
Anyway, all the other stuff I’ve gone through doesn’t matter. I have been looking at dozens of headlamps on Amazon. All under $25. All using rechargeable Li-ion 18650 batteries because I now have 6 of those and two chargers, so I’d like to keep everything as interchangeable and compatible as possible.
Something like 85% of the headlamps I’ve looked at had comments from people saying that the stated lumens were bullshit. Not that the lamps aren’t bright, just that the the lumens claimed, by every company, on every headlamp (with lumen claims over 1200, which are the only ones I’m looking at) are a lie. By thousands. So two questions:
WTF?
Is there a means of determining what the lumens actually are, a means available to normal folks?
My other question is about diffuser lenses Do they make an actual worthwhile difference? The claim is that it widens the beam.
The lumens are overstated for both example lights, probably by a factor of 5.
With a zoomable lamp you lose lumens in the lens system. You get a nice beam, but at a small sacrifice.
You really should join a flashlight forum so that you can get the headlamp that you need, and to help you differentiate from the junk that is advertised on Amazon. And to get some lessons on battery safety.
Lumens aren’t really the whole story as to the brightness of a flashlight or headlamp.
The ANSI FL-1 standard measures multiple parameters, of which lumens is just one. And it’s not the lumens at a point; it’s total lumens emitted, so if the light has a very wide, diffuse beam, it may well be 500 lumens, but spread out evenly over a 60 degree cone, i.e. not terribly bright in any one area. Similarly, a 150 lumen light focused with a very good parabolic reflector and lens will probably seem brighter than the 500 lumen light described above.
You have to take into account the peak beam intensity and beam distance measurements along with the lumens to get a better idea of the actual light’s beam.
The units and measures of luminous and radiant flux are many and confusing. You can start with Wikipedia, whose definition is straightforward. Note that lumens are a measure of luminous flux, meaning that it measures light that you can see. radiant flux, by comparison, measures all electromagnetic output from ultraviolet through near infrared. For headlights, luminous flux is obviously the measure of choice, because you want a measure of the light you can see.
Units and measures get complex because you can measure flux per unit area of the source, or per unit area that it’s falling on, or the flux per unit solid angle, or the spectral flux that occurs between two given wavelengths, or combinations of the above.
lumens measure the total luminous flux coming out of the source in all directions, so it’s pretty straightforward in that way.
as for measuring it, you could buy a fluxmeter, but that’s a pretty specialized piece of equipment that you won’t have much alternative use for afterwards. and I doubt if anyone will loan you one. You’d probably be better off seeing if a photographer will loan you his or her light meter.