Educated Guesswork

Lights for Running

*Expanded version of twitter thread

Most serious runners find themselves running in the dark at one time or another. The most common reason is because you need to squeeze in a workout before or after work -- especially in the winter -- but there are plenty of ultradistance events (100 miles, 24 hrs, etc.) that are likely to have you out overnight. In either case, you're going to need some lighting. There are three major options here:

  • Hand-held flashlights
  • Headlamps
  • Waist-mounted light

As a practical matter, headlamps seem to be the dominant choice, probably because hand-helds are a pain and waist-mounted lights are kind of a boutique product. I've had a number of people ask me what kind of headlamp to buy, so here's a brief overview of the space.

Tradeoffs #

Headlamps have gotten a lot better over the past few years due to improvements in LEDs and batteries but the fundamental fact is that making light consumes power and the brighter the light the more power it consumes. More power storage means more battery, which means more weight. The result is that selecting the right headlamp is a compromise between weight, brightness, and burn time. In general, you want to carry the lightest headlamp which will burn at the brightness you need for the time you need.

There are two main variables you have to consider:

  1. The terrain you are going to be running on.
  2. The amount of time you will be running in the dark.

Brightness is mostly determined by terrain If you're going to be running on the road or really smooth trail, I generally find 100-200 lumens or so to be enough. On technical trail, you can get away with 200 lumens, but I prefer 400 or so. 1000 lumens is better, but you're going to pay for it in weight and also will start blinding anyone coming the opposite way.

There are three main scenarios in terms of burn time:

  1. Running in the morning before sunrise
  2. Running in the evening after sunset
  3. Overnight runs (this is most common in ultramarathons over 100K)

In the morning, it's pretty easy to figure out how much burn time you need: just subtract the time you start from the time when sunrise happens, plus perhaps a little slack. The good news here is that if you overestimate and run out of battery, it's not usually that big a deal: it's probably going to happen towards dawn anyway, and in the worst case you can just walk or stand around till it gets bright enough to see. The evening is a little different because there's uncertainty about how long you'll be out. If you underestimate how long you'll be out -- for instance if you fall and have to walk it in -- or overestimate your burn time then you can get stuck out in the dark, which is not good. For this reason, you'll want a fair amount more slack or to carry a backup light (see below).

Overnight runs are conceptually like running in the morning: you know when sunrise is and you need enough burn time to last you the whole night. This likely means you'll need some sort of spare batteries. For instance, the Lupine 3.5Ah/25Wh battery weighs 120g, which, combined with the lamp head, is about as much weight as you want to have on your head at once, and gives you 650 lumens at 6 watts and 350 lumens at 3 watts. So you could just barely make it all night on 350, which is a little dim, or you'll need two batteries. To be honest, that's probably better anyway: changing batteries is fast and you'll be happier with weight in your pack than with it on your head. One thing I want to note here is that for an overnight run it's not just the ability to see the trail but also keeping yourself awake: in the middle of the night your body is going to want to sleep and having a really bright light seems to help me fight that.

Battery Type #

There are two main battery choices: disposable batteries (lithium are the best here because they're the lightest) or rechargeables. For short duration runs, I definitely recommend rechargeable. That way you can burn down part of the battery and then charge it back to 100%. If you're using disposable, then there's a good chance you use 60% or so, and then you might not have enough for your next run, plus you have a lot of uncertainty about how much light you have left. For longer runs where you're going to run through your entire battery pack anyway, it may be cheaper to just buy disposables rather than having multiple rechargeable battery packs.

Historically, you mostly had to choose when you bought the light because it either came with a battery pack or it took separate batteries (typically AAAs). A number of headlamps, such as the Petzl Actik Core now come with hybrid systems where they have a rechargeable battery pack but will also take regular batteries. This has the advantage that you can use the rechargeable pack for daily usage but carry disposables as backup or if you have a longer event. If you're going to be going overnight, this seems like a good option. You might also be able to use a headlamp that takes regular AAAs and put in rechargeable AAAs, but the one time I tried it, they seemed to be slightly larger and I had trouble getting them to fit, so you'd want to test this out for yourself.

You'll notice I haven't talked about lights failing. This can happen, but modern LED headlamps are very reliable, so this is less of a concern than it might otherwise be.

Battery Placement #

Because a significant part of the weight of a headlamp is battery -- especially if you want a lot of burn time -- the location of the battery affects the balance of the headlamp. There are two major options here:

  • Directly in the light in a single unit on the front of your head.

  • In a separate pod on the back of your head.

The front of your head is a good option for relatively dim lamps or those with short burn time, but if you want a bright lamp and long burn time, you're likely to end up with a pod on the back of your head. Otherwise the lamp gets too heavy and tends to press against your forehead uncomfortable -- at least it does for me. You can also get battery packs with longer cords which you can carry in your pack or maybe on your waist, but this seems like just another thing to mess around with. For instance, it means that if you want to take your pack off for some reason now you have to take the batteries out of the pack, which I expect will be a pain; I already have experience with this with wired headphones connected to a phone in my pack, so I'm not eager to add another cable attaching my head to my pack.

Beam Shape, etc. #

The total light output in lumens is really important, but it's not the only thing. Beam shape also matters: I like a fairly bright center spot but based on the lights I've seen, others seem to like a more broad diffuse beam. Another question is whether you want a constant beam or one that reacts to environmental conditions, for instance getting bright when you are looking further away. Petzl offers a number of lights like this, but I personally prefer a constant beam and find it annoying to keep having the amount of light changing depending on where I look; that happens enough just from your head moving around.

Remote Configuration #

A number of the higher-end lights can be remotely configured with a mobile app. For instance, you can set the number of brightness levels and how bright they are. This seems somewhat useful in principle, though to be honest I've not been that impressed. When I initially got a headlamp with this feature I fiddled with it a bit but at the end of the day the factory settings are probably fine unless you're the kind of person who really likes to tune everything.

Recommendations #

Ultimately, this is all a matter of personal preference: If you're going to be wearing a headlamp regularly, I would advise trying several headlamps to see what you like in terms of comfort, beam shape, etc. The headstraps in particular have a lot of impact on comfort, but everyone's head is different. With that said, I do have some recommendations/thoughts.

My standard headlamp is a Petzl Actik Core. It's 450 lumen at brightest and is rated for 2hrs at that level. As noted before, it comes with a rechargeable battery but will also take separate batteries. I've used it regularly for pre-dawn runs and would also feel comfortable with it for the beginning and end of a 50 mile or 100K race where you started before it was light and might finish in the dark. I used this light for Rim-to-Rim-to-Rim and they were plenty bright to use for the South Kaibab descent. I'm less certain I would want this light for an overnight event: 450 lumens is on the bottom end of brightness for that. One thing I don't love about this headlamp is that it's hard to adjust the brightness: pressing the button just cycles you through brightness levels, including off, so that makes it a bit of a pain to dim the light: once it's on max, the next click takes you to off and now you're in the dark.[1]

I also have a Lupine Piko (the somewhat older 1500 lumen version). It's reasonably light (the new version is 180g with the 3.5 Ah battery) and ridiculously bright (the new version is 1900 lumens); basically you're wearing a car headlamp on your face. As a practical matter you almost never need a light this bright for running, though it's nice to have the option of a really bright beam for technical sections or when you're tired.. It's fantastic for cycling, though, and you can get a helmet mount for the Lupine head unit. I've worn this for a number of overnight events and it's very comfortable and you don't really notice it on your head. With that said, the Lupines are quite expensive and I bought this a while ago, so while it's served me well I don't know if it's the best choice today.

If you are going to run on the road, you can probably get by just fine with an ultralight headlamp around a few hundred lumens. I've heard good things about the Petzl Bindi which gives you 2 hours at 200 lumens in a ridiculous 35g package. This kind of light is also useful as a backup light to carry in your running pack. I strongly recommend doing this if you're going to be doing any long distance stuff: your regular light might fail in some way or you might run into someone whose has. In at least two events I've run into someone who needed a light and had to lend them one. I usually carry a Petzl e+Lite for this purpose. It works OK but maxes out at 26g; today I'd probably carry a Bindi, which is only fractionally heavier.

Like I say, this is all kind of personal, so what works for me may not work for you. The good news is that REI, Backcountry, etc. sell most of the major brands like Petzl and Black Diamond so you can try out different units for yourself and return/exchange if you don't like them.

  1. Incidentally, it's easy to get fooled by your light about how much ambient light there is. On more then one run I've thought "hey, I don't need this light" and then covered it and realized, "nope, it's still dark". ↩︎

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