Hi all, first post in here for a long time!

I'm looking to buy a more powerful headlight for my bike, since the light I have at the moment is more to make sure people see me rather than to see where I'm going. The problem I'm running across is that there seem to be several different units used to measure how much light a headlight produces. I've seen lumens, lux, and candlepower all used to describe lights, and frankly they've got me stumped.

Is it just a matter of multiplying by some constant, like converting between miles and kilometres?

If not, what's the deal?

Thanks in advance!

I think lumens is the standard these days, but even then you're not sure what you are getting. Is it max lumens or usable lumens?

And then there seem to be a few ranges that are important:
Damn that's bright,
Hot Damn that's bright,
OMFG that's bright
and lastly turn that damn light off you're blinding me.

These correspond to 300 lumens, 600 lumens, 1000 lumens and 1500 lumens.

But really, if you haven't looked in a while, they are so much brighter than before and you can get some really cheap ones that'll outshine anything available just last year. The one I have is $34 and is rated at 1200 lumens, but I'd say it is an effective 600 or so. It doesn't matter as it is still a lot of light for the buck.

https://www.ebay.com/itm/251060235556...84.m1497.l2649

"Usually", when they don't mention lumens, the lights are cheap and not very bright. Lumens are supposed to be the total light given off. Lux is light per area, so a very narrow beam could have larger lux than a very bright light that is spread over a wide beam.

The MTBR Lights Shootout measures lights with their own lux meter, and they are attempting to use the same measurement of total light output on all their lights, so they can be compared to each other. Some manufacturers are pretty accurate in their lumens, and other exaggerate a lot.

But each doubling of lumens only makes the light look "a little" brighter. So, for instance, the difference between 450 lumens and 600 lumens isn't real big.

I would look for 500-600 lumens to light up the road at normal road bike speeds. I have 1100 lumens that are great in the city, lighting a big pool of light on the road and competing with car headlights. But it's often too bright on very dark country roads, so I run it on medium, about 500-600 lumens. ( You can always run a light on medium or low, so it's good to have lots of lumens--for downhills or competing with car headlights in the city)

When I was looking at the lights reviews, I paid a lot of attention to the beam spread. Some lights, especially flashlights, have a central bright spot, with a surrounding dimmer area that cuts off suddenly at the edge. I like a beam that gradually tapers off at the edges, with no bright spots or dark lines showing.

( I used to use a 200 lumen light and it wasn't quite bright enough to go 18-20 mph and see potholes in time)

Lumens is the amount of light, lux is the intensity at a particular point in the beam pattern.

The beam pattern is important. I've had lights with lots of lumens, but the beam pattern is a flood beam, and the result is that the area right in front of the bike is disproportionately bright. My eyesight auto-adapts to the bright area. Then it's hard to see at longer distances, to pick out obstacles with enough time to react. More lumens, the problem is simply magnified. Flood beams are great for off-road riding, where the bike may get aimed all over the place and the stuff right in front of you is in fact the main concern.

For road riding, a more "center-weighted" beam works better. Aimed at a wall, it generally looks like a strong spot with a corona, unless you're looking at a shaped beam typical of some dynamo headlights, in which case it would be more trapezoidal. Played out across 100 meters of roadway at an angle, the strong center spot is covering a large area at a distance, so it makes sense for most of the output to go there.

As Einstein says, everything should be made as simple as possible... but not simpler You won't get the complete story by comparing lumens without looking at how they're being distributed onto the road.

Lumens is what you want.

https://en.wikipedia.org/wiki/Lumen_%28unit%29

Thanks a lot guys! I've taken your advice and looked for something with a lot of lumens, but with less bright settings as well. I've found this on eBay, but the price looks ridiculously low for what it is, which makes me suspicious. Any thoughts?

Better has the battery and charger.
https://www.ohotdeal.com/inbike-3-mod...ght-torch.html

That's the type of light that you want, but as mentioned above you'd need a battery and charger. The one I posted way up above has 2 batteries and the charger, and a head mount as well. The head mount can be adapted to be a helmet mount if that's what you want. Also, the U2 variety is about 10-20% brighter than the T6, but you wouldn't go wrong with either.

I just purchased a light. I considered a light with a removable battery and external charger but decided upon a dedicated bike light with built in charging circuit. I didn't want to bother with taking batteries out of the light to charge them. I also wanted a foolproof design. Lithium batteries have been known to 'vent with flame' when charged improperly. I probably worry too much, but if something can be done wrong, sooner or later I will do it wrong.

Ah, that's a point, a rechargeable battery would be a lot cheaper than feeding the damn thing AAAs like there's no tomorrow.

I'll keep looking, but thanks for all the help!

That's a good system for the money.. I think the whole deal is less than $20. I run the same mount, and 18650 and 26650 lights. they are bright, and cheap..If I was you I would get that system as a first system. It is bright. Most 18650 torches are super bright. The zoom works well if it doesn't react to bumps.

I bought my first strong headlight earlier this year, a 200 lumen Cygolite. I think 150 lumens is the bare minimum to be able to see by, and that is marginal. 200 (or more) is preferable and I am now normally teaming my Cygolite up with a 200 lumen flashlight. The different beam patterns with a total of 400 lumens work well together to light up the road ahead and two lights gives me some redundancy.

Looks good, is that bright enough? Anyone used this?