Electronics, Lighting, & Gadgets - Not noticing much of an advantage of 2 vs 1 FENIX

I used to run 2 FENIX lights - one on the head and one on the bars.

I've since switched to only one on the head, and find that it alone more than suffices. The additive effect of 2 FENIXs aren't so impressive, since they just overlap. In fact, I notice no difference in riding with only one Fenix.

Just wondering if anyone had any experience similar to mine, or encountered situations where the extra handlebar torch was really critical.

No, but where do you do your riding? Lit streets or darker?

I used to run 2 FENIX lights - one on the head and one on the bars.

I've since switched to only one on the head, and find that it alone more than suffices. The additive effect of 2 FENIXs aren't so impressive, since they just overlap. In fact, I notice no difference in riding with only one Fenix.

Just wondering if anyone had any experience similar to mine, or encountered situations where the extra handlebar torch was really critical.

No, I am noticing the same thing. I have two L2D Premium lights on my bike (and one on my helmet). For the two mounted to my bike I find that running one on turbo (175 lumens) is almost as good as running two on turbo, and that running one on turbo is better than running two on high (100 lumens).

My morning commute is two hours. For some reason I am only getting 1.5 hours of run time out of my 2650 AA batteries. I'll run one on turbo for half the distance and then turn the other one on.

The helmet light is always on the high setting.

No, I am noticing the same thing. I have two L2D Premium lights on my bike (and one on my helmet). For the two mounted to my bike I find that running one on turbo (175 lumens) is almost as good as running two on turbo, and that running one on turbo is better than running two on high (100 lumens).

My morning commute is two hours. For some reason I am only getting 1.5 hours of run time out of my 2650 AA batteries. I'll run one on turbo for half the distance and then turn the other one on.

The helmet light is always on the high setting.

That's been my observation on lights since I started this foolishness of riding at night. Although I've been handed my head recently in discussions here, I find that a single source of light that is twice as bright as 2 different sources performs much better. The light hitting the ground really is twice as bright for a single bright source and the light from 2 different lights is noticeably dimmer.

I had always read that if you could only have one light, you should put it on the bars.

Since I have started night riding, I would have to disagree. I want light pointed at where I am looking and on the helmet is the only way to get that.

Forget about whether two allows you to see better than one. I believe in redundancy in case one goes out.

For safety, you can tell the difference between a car coming at you with only one headlight working versus two. You can certainly be seen better by cars if you have two lights.

Aim the bar light at the right edge of the road so that you are able to see critters that may be waiting to jump out at your. Motorcyclists that have supplemental headlights generally aim the right one that direction.

or encountered situations where the extra handlebar torch was really critical.

Handlebar lights cast shadows on stuff that has height or depth. Helmet lights don't, unless the object is suspended above the ground.

As an illustration, take one of your lights and look down a dark staircase while holding the light above your head like a helmet light. Now lower the light to waist level. Aha, now each step on the staircase is clearly highlighted by a shadow, eh :)

In similar fashion, bar-mounted lights help identify rocks, potholes, lumber and other road hazards. In snow, the bar-mounted light helps identify ruts, ridges, etc that need to be avoided. So those might be some reasons to keep your handlebar light, not to mention that it helps increase your visibility and gives you a second light if one runs low on battery power.

Handlebar lights cast shadows on stuff that has height or depth. Helmet lights don't, unless the object is suspended above the ground.

As an illustration, take one of your lights and look down a dark staircase while holding the light above your head like a helmet light. Now lower the light to waist level. Aha, now each step on the staircase is clearly highlighted by a shadow, eh :)

In similar fashion, bar-mounted lights help identify rocks, potholes, lumber and other road hazards. In snow, the bar-mounted light helps identify ruts, ridges, etc that need to be avoided. So those might be some reasons to keep your handlebar light, not to mention that it helps increase your visibility and gives you a second light if one runs low on battery power.

+1 on this logic. However, my application is to place one on the bar and one on the helmet. Better for low obstacles and better for redundancy.

My morning commute is two hours. For some reason I am only getting 1.5 hours of run time out of my 2650 AA batteries.

If you happen to have a LaCrosse BC-900 or another decent battery charger that can condition the cells, run them through the conditioning program. My Sanyo 2700s went from about ~1600mAh (when brand-new) to over 2700mAh capacity after the LaCrosse was done with 'em.

Conditioning takes time (by which I mean, days), so plan for that :) The charger first drains the cells, then recharges them and notes the total capacity, then drains them completely again, charges them completely again, and compares the new capacity to the previous run. Over and over. Once it hits the point of no further improvement, it charges up the batteries one last time and reports the total mAh capacity.

+1 on this logic. However, my application is to place one on the bar and one on the helmet. Better for low obstacles and better for redundancy.

yup. almost zero depth perception when the only light is on your head.

fine for stuff you know, school of hard knocks for new trails (especially offroad)
or new potholes.

stuff that looks flat at speed can be big enough to knock you on your face


single light ? the safest high-speed option is on handlebars.

if you are on trail and turning tight enough where you may wish for a head mounted light, you are going slow enough so it really doesn't matter (but I have extremely good peripheral vision, YMMV)

Two lights of the same brightness will never appear to be twice as bright as one of the lights, because perceived intensity is logarithmic. In other words, if you have a 500 lumen light, things won't appear twice as bright until you've got 2000 lumens, or four times the intensity of the original source. This is part of why I haven't invested in a second P7; I know I wouldn't be twice as satisfied with it/them as I am with my single light. I plan to hold off from another front light purchase until a 1000 lumen flashlight comes along in the $50 range.

Good thinking uke, I am going dual P7s but more for the beam shaping possibilities than the crazy output.

If going with two lights, does it make sense to put one with more spill down low and one with more throw up high?

I have a Fenix L2D on the handlebars, but dislike how it blinds folks on the MUP due to the lack of a cut-off. Would moving this low on the fork help? I'm mostly on the road.

Good thinking uke, I am going dual P7s but more for the beam shaping possibilities than the crazy output.

Yup, I can see the value in that.

That's been my observation on lights since I started this foolishness of riding at night. Although I've been handed my head recently in discussions here, I find that a single source of light that is twice as bright as 2 different sources performs much better. The light hitting the ground really is twice as bright for a single bright source and the light from 2 different lights is noticeably dimmer.


I remember that thread. Some of the shots came from people whom "like you" I've come to respect their opinions. I'm glad to see that it hasn't kept you from posting and sharing your knowledge.:)

yup. almost zero depth perception when the only light is on your head.

fine for stuff you know, school of hard knocks for new trails (especially offroad)
or new potholes.

stuff that looks flat at speed can be big enough to knock you on your face


single light ? the safest high-speed option is on handlebars.

if you are on trail and turning tight enough where you may wish for a head mounted light, you are going slow enough so it really doesn't matter (but I have extremely good peripheral vision, YMMV)

Sorry but I've used helmet lights alone on a few occasions when I've had a failure. I've never had trouble distinguishing obstacles even when riding off road with only a helmet light. I don't really notice the shadows doing anything significantly different.

I do use helmet lights in conjunction with bar lights. On corners the only light illuminating into the corner is the helmet light and my vision is unimpaired. The only time I've ever noticed weird shadows with lights is when I attempted to mount the lamps lower than the handlebars. Then it was like riding in a western movie gunfight with incredibly long shadows that hid all kinds of stuff.

The only time I've ever noticed weird shadows with lights is when I attempted to mount the lamps lower than the handlebars. Then it was like riding in a western movie gunfight with incredibly long shadows that hid all kinds of stuff.

Haha. Great analogy.

I use two lights for DIFFERENT purposes. I keep the dinnote on the bars to see and the fenix on the helmet to be seen.

Sorry but I've used helmet lights alone on a few occasions when I've had a failure. I've never had trouble distinguishing obstacles even when riding off road with only a helmet light. I don't really notice the shadows doing anything significantly different.

I do use helmet lights in conjunction with bar lights. On corners the only light illuminating into the corner is the helmet light and my vision is unimpaired. The only time I've ever noticed weird shadows with lights is when I attempted to mount the lamps lower than the handlebars. Then it was like riding in a western movie gunfight with incredibly long shadows that hid all kinds of stuff.

Regarding road riding as I stated previously I agree 100%. Regarding off-road, which the OP did not ask about but others have brought into the discussion, I have no experience and therefore no opinion.

Two lights of the same brightness will never appear to be twice as bright as one of the lights, because perceived intensity is logarithmic. In other words, if you have a 500 lumen light, things won't appear twice as bright until you've got 2000 lumens, or four times the intensity of the original source. This is part of why I haven't invested in a second P7; I know I wouldn't be twice as satisfied with it/them as I am with my single light. I plan to hold off from another front light purchase until a 1000 lumen flashlight comes along in the $50 range.

Much as I like to agree, I don't think the perceived intensity is a logarithmic function. The definition of a lumen is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. That definition already takes into account our perception. Additionally, it's pretty easy to tell the difference between two light sources. I've run lights all the way from 180 lm to 1500lm and can easily tell when one light is twice as bright as the other. The difference between 180 lm and 300 is very striking. A 500 lm light is very bright but a 1500 lm light is extraordinarily bright.

Perhaps the differences that I notice between 2 700 lm lights and one 1500 lumen light have more to do with looking at them in a dynamic situation rather than a static one. Seldom does a 2 source system line up so that both lights are hitting at the same spot while riding a bike. Such is not the case with a 1500 lm source. It is always putting the total output in the same spot

if you are on trail and turning tight enough where you may wish for a head mounted light, you are going slow enough so it really doesn't matter (but I have extremely good peripheral vision, YMMV)

That's not my experience. I started off with a bar-only mount, and even with going slow, I still wanted light where I was headed to avoid debris and make sure I didn't end up in the ditch. Also, depending on the beam characteristics (spot vs. flood), having it off-center much at all can reduce the illumination quite a bit in the direction you're headed. So if you're going 15mph into a turn, you can't see where you're going.

Another reason I like one on my head is for shining it at drivers who don't seem to see you, and for checking out areas at the side of the trail/road that might be hiding rodents preparing to dart under your wheel.

I can say for sure that I really, really prefer the light to be aimed, and I've done both.

Much as I like to agree, I don't think the perceived intensity is a logarithmic function. The definition of a lumen is the SI unit of luminous flux, a measure of the perceived power of light. Luminous flux differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light. That definition already takes into account our perception.

Well...the definition accounts for *wavelength sensitivity* perception differences, but not for intensity normalization perception differences. That's the "perceived power" they're accounting for, differences in wavelength only. They're not accounting for the inherent effect in which human vision intensity perception is logarithmic with power output.

Going through the Wiki page you quoted, 1 lumen is equal to one candela emitted into a particular conic angle (a steridian). One candela is measured as an emitted light power (measured in Watts) at a specific wavelength. That's where your wavelength perception comes into play, by defining the wavelength at which we take the measurement.

However, that definition is still inherently based on power. But uke is right, perception is logarithmic, because you can easily distinguish a dim light in darkness, but you can't pick up a dim light in a bright background. If perception were linear with power, those tasks would be equally difficult, but they're clearly not.

So that gets us back to the question, are two 100L lights as good as a 200L? If they all have the same beam patterns, and you can get the two 100Ls perfectly overlapped, then the answer based on the above would be "yes". They would give you the same light output in the same directions. If the two lights don't work as well, it could be because you can't get them overlapped well, or because psychologically you expect two lights to be better than one.



Perhaps the differences that I notice between 2 700 lm lights and one 1500 lumen light have more to do with looking at them in a dynamic situation rather than a static one. Seldom does a 2 source system line up so that both lights are hitting at the same spot while riding a bike. Such is not the case with a 1500 lm source. It is always putting the total output in the same spot

I think that perfectly explains the situation. For what it's worth, the "2 weak vs. 1 strong" experiment is probably easier with floods as opposed to spots for that very reason.