Black Diamond Icon Polar
Historic Range: $44.93-$99.95
The Black Diamond Icon Polar is a high tech headlamp…
Source: received for testing via the Trailspace Review Corps (sample provided by Black Diamond for testing and review)
The Black Diamond Icon Polar is a high tech headlamp featuring a wide range of brightness levels (4 to 200 lumens) and easy, continuous adjustment of brightness. It is intended for use in extreme cold activities, but can be used in any temperature range. The battery case is mounted on a strap so it can be worn over your shoulder, reducing the amount of weight on your head to less than 3 ounces, or inside your parka for extreme cold conditions. The Black Diamond Icon is the same headlamp with the battery case mounted on the back of the headstrap instead of remotely on a shoulder strap. Black Diamond has long been known for their high performance headlamps.
Note -30°F followup test, described at end of discussion - the Icon Polar separate battery pack is an excellent answer to subzero temperature operation.
- Bright focused Quadpower LED, dual singlepower LEDs, and dual red LEDs, continuously adjustable for lighting conditions, plus emergency strobe of the singlepower LEDs
- On brightest setting of Quadpower LED, excellent for route-finding for pre-dawn approaches or those late night descents back to the trailhead, as well as bicycling and nighttime running events.
- Dual single power LEDs are excellent for map reading or for reading when tent-bound or bivouacking.
- Lithium and Alkaline non-rechargeable AA, and rechargeable Lithium, NiMH, and NiCd AA batteries can be used.
- Power button can be locked to prevent accidental turn-on in pack.
- Battery case can be carried in the included pouch inside your layers to keep the batteries warm in sub-freezing conditions
- Requires 4 AA batteries.
- Long cord to battery case can interfere when changing clothing layers.
- At full brightness on busy trails, oncoming hikers will be blinded temporarily, often complaining loudly.
Weight: 10-7/8 oz / 308 g (total); 2-7/8 oz/81g (headlamp on headstrap)
Suggested price: $89.95
Warranty: 3 years on defects and workmanship
Background: I should note that a significant part of the general discussion of headlamps and my testing method overlap with my recent review of the Petzl NAO. The headlamp specifics differ, of course, since the Icon Polar and NAO represent very different philosophies and approaches to the outdoor performance lighting problem.
Over the years, I have used everything from candle lanterns, kerosene lanterns, and carbide headlamps through various battery-powered miners’ headlamps to the current lightweight LED headlamps for backpacking, making approaches to climbs, and skiing, as well as commuting by bicycle. This has included a number of headlamps by various companies, many of which I have roundly cursed in the dark of the night when they failed me. Over the past 10 years or so, headlamp technology has made huge leaps forward in dependability and light weight (thanks to the brightness and efficiency of LEDs and improvements in batteries, both standard lithiums and rechargeable lithiums and NiMH).
For many outdoor activities, whether on the trail or in camp, having a light source that is dependable is vital. I heavily use lights for approaches, returning to the trailhead or camp after a long day, reading the map or climbing topo during the climb, or a book while holed up in the tent. There are several requirements I have for a lamp:
- The batteries must last long enough to provide light during the full duration of the trip, including any delays.
- It has to provide an appropriate level of light during the various stages of the trip.
- It has to be light enough weight to be comfortable to wear, or for a tent light, have a convenient way to hang it.
- For map reading, the color of the light has to render all the map colors clearly (I have had the experience of a light with a yellowish or reddish tint making yellow or red markings almost invisible or in some cases producing a color shift that masked details).
- It has to be durable enough to survive the rough handling that inevitably happens during an expedition.
- It has to be easily found in the pack (none of those tiny black LED lights that hide inside a black pack!)
- For my winter, high altitude, and polar trips, it has to perform at low temperatures.
- The final question is “Do I really need a headlamp this bright, this adjustable, and this expensive?”
I have had a number of Black Diamond headlamps over the years, and noted the annual increase in brightness (typical of electronic gadgets these days). One shortcoming has been that most previous LED headlamps had the batteries in the lamphead, thus exposed to the cold, resulting in a loss of battery power in a short time. So when Trailspace’s Chief of Gear Reviews, Seth, asked me to review the Polar version of the Icon, intended for use in extreme cold conditions, I leapt at the chance. Like all the most recent high-powered headlamps, the list price is pretty stiff, though based on my tests, well worth it.
Since I received the Icon Polar in the fall, during cool, but not cold, weather, this is a preliminary report, to be updated after I get some “snow-time” in with the Icon Polar. Lowest temperatures encountered during this part of the test were in the low 40° range, with wind chill only down to the low 30° range.
The Icon Polar arrived in a box designed cleverly to protect the contents against shipping damage, but with minimal materials, all recyclable. Included were the Icon head with headstrap, the battery case, a pouch for the battery case with a long shoulder strap and belt, a set of 4 Energizer alkaline batteries, and an instruction sheet.
Basic operating instructions and specifications are also on the box and on a small sheet of paper that could be carried in a shirt pocket. The instructions are simple enough that you can learn them in a couple minutes of playing with the power button.
The first step, after unpacking the box, was to insert a set of batteries, familiarize myself with the various functions and adjustments, and check the battery. After playing around with the headlamp a bit, I read the directions, which come in 6 languages, 4 of which I can read (good practice for improving fluency), one I struggle with, and one which I have no comprehension of at all.
Specs and Features: By holding the power button down when the LED is lit, you can adjust the brightness between 4 lumens and 200 lumens. At the minimum 4 lumen brightness, BD rates the battery life at 175 hours for the QuadPower LED and 250 hours for the dual SinglePower LEDs. At the 4 lumen minimum, the visibility range for the QuadPower is rated at 14 meters, while the dual SinglePower LEDs go to 4 meters.
The difference is that the QuadPower has its 4 lumens concentrated into a small cone, while the SinglePower pair have their 4 lumens spread in a diffuse fashion (hence lower lux at a given distance, still plenty of light for map or book reading). Maximum brightness is rated at 200 lumens for 75 hours for the QuadPower LED and 35 lumens for 75 hours for the SinglePower pair.
The headlamp can be “locked” to prevent accidentally turning the lamp on in your pack. I have had dead batteries on flashlights, GPS receivers, MP3 players, cell phones, and ham radios more than once due to the switch being accidentally depressed in the pack or a pocket (many devices have poor switch designs that allow accidental depression, as more than one friend has found out with PLBs and PLB-type devices).
I next wore the headlamp for several walks at night around the neighborhood and for several night hikes in one of our local parks that allows after-dark hiking.
Details of Testing:
Getting familiar with the controls of the Polar was straightforward, involving simple button pushes and holds. The first button push turns the QuadPower LED on to maximum brightness. The second push turns the headlamp off. The third push turns on the two single-power LEDs, and the fourth turns them off. Holding the button for a few seconds from the off mode switches to the red LEDs, with subsequent pushes turning them on or off.
To return to the white-light mode from the red-off mode, simply hold the power button for a few seconds until the QuadPower LED flashes. The emergency strobe mode of the SinglePower pair of LEDs is turned on in the white-light mode from the off status by pressing the power buttons 3 times in quick succession. A simple button push stops the emergency strobe.
The lamp head does get warm to the touch, as is common with high-power LEDs. But I did not find it to be hot, as some bright LED lamps become.
Water Resistance: BD rates the Icon Polar at IPX7 for water resistance (immersion to 1 meter for 30 minutes). This is of significance for many of the intended activities, which are likely to involve heavy rain or snow, as well as wet snow, not to mention the potential of accidentally dropping it in a stream or lake. BD recommends rinsing the Icon Polar with fresh water in case of wetting with salt water, but not using a power washer.
Visibility Distance: BD specifies 100 meters as the visibility distance at their maximum 200 lumen setting. My preliminary distance tests consisted of going to one of the few parks around here that allow night entry (but be out by 10 PM!). To provide an easily seen target for judging visibility distance, I took our BearIKade with the reflectorized tape we have put on it (the tape will make it easier to locate in case a bear tries to carry it off into the bushes). I also went out for a few walks around the block, during which I discovered that I could easily see our California reflectorized license plates and stop signs up to most of a block away.
Our area has standardized 1/8 mile blocks, so I was spotting the reflectors well over 100 meters away. Of course, this is not like seeing details that far away in the dark woods or on a mountain trail, since stop signs and reflectorized license plates are intended to be seen at long distances. This will prove handy in finding the tent when returning after dark, since I have the reflectorized guy lines on all my tents, plus most of my tents have reflectorized tie-down straps. During my long hikes (described later), I did find that I could spot animal eyes at long distances as well.
I took a number of photos with my Nikon D300s, standardized at 1 second, f/3.5, and ISO 1000 for easy comparison of different visibility distances. This worked quite well, as can be seen in the Mission Peak summit shot below.
Radio Frequency Interference: Unlike the Petzl NAO I reviewed a few weeks ago, I did not encounter any RFI (Radio Frequency Interference) affecting the photos. Readers of my review of the Camelbak AllClear UV water purifying system will recall my comments on RFI with electronic devices as more and more outdoor gear incorporates electronics.
Black Diamond does include the required FCC notification in the instruction sheet and on the packaging. I checked the Icon Polar for interference with my avalanche beacons and other electronic devices, and indeed found that close proximity to the lamp head introduces a small amount of noise (much less than the Petzl NAO). The interference can be eliminated by turning the headlamp off or reduced by moving the avy beacon or other device away from the headlamp.
Since, even with a night SAR mission, you would not hold an avy beacon next to the headlamp, I do not consider this a serious problem, but one to be kept in mind. My only caution here is to be aware of the possibility when using any electronic gear (cell phones, handheld radio transceivers, cameras, avy beacons, PLB, etc) in close proximity to the headlamp.
Lumens and Lux: In comparing the Icon Polar to other headlamps, I found that Black Diamond and other companies which use the European standards organization approach (CE) specify brightness in lumens, while some companies give their specification in lux. If you are not familiar with light measurement, this can be confusing.
To oversimplify a bit, lumen is a measure of total light output, while lux is a measure of light “density”. The two are related in that 1 lux is 1 lumen per square meter. Since the intensity (or think of it as the energy density) falls off as the square of the distance, the light falling on a 1 meter square white test card at 10 meters is 4 times as bright as on the same 1 meter square card at 20 meters, measured in lux. The total output in lumens is usually included in the instruction sheet or on the packaging to specify light output of the headlamp.
The amount of light falling on an object is also dependent on the cone angle of the beam as well as distance from the headlamp. In some older incandescent and halogen headlamps, the cone angle could be varied by screwing the reflector in and out (often called “focus”, though there is no actual focusing involved). None of the current LED lamps are adjustable in that sense.
The Icon has three sets of LEDs, the Quadpower with a relatively narrow cone of light shaped by a fixed reflector, the singlepower white and red pairs of LED being simple diffusion arrangements. The red LEDs are colored to reduce interference with night vision. I should note that, although red lighting has been used for night vision for more than a century, vision experts still dispute whether color is the important factor or simply light level.
Most manufacturers, including Black Diamond, also state a visibility distance. Since this is normally determined according to the European standard, this is a reasonable way to get a relative comparison. The CE (European standards organization) specification uses the distance at which the brightness of a test card illuminated by the headlamp is that produced by the full moon (on a clear night, of course, not like our typical San Francisco area foggy nights). The full moon provides a 0.25 lux illumination. My presbyopic eyes can read the second or third level headlines on the New York Times by the light of the full moon, but not the fine print of the stories (yes, I actually tried this). Maybe you youngsters can read the fine print by the full moon, though. I do find the full moon to be adequate for hiking on most Sierra trails in the open or on glaciers and snow fields.
Lighting levels for all 3 LED sets are altered by holding the power button down when that LED set is on. An electronic rheostat decreases the brightness gradually to the minimum 4 lumens, then increases back to the maximum. You simply stop at the level you need at the moment.
Battery Life: Running the light at a lower level increases battery life from a specified 75 hours to 175 hours for the QuadPower, and from 25 hours to 250 hours for the SinglePower pair, depending on the batteries you are using.
I first used a set of fully charged Eneloops (NiMH, 2000mAh), a rechargeable that I have found quite dependable, leaving the Icon turned on continuously to the maximum setting of the Quadpower LED. The headlamp began to noticeably dim at 28h30m, becoming unusable at 41 hours.
I next tried the included set of Energizer alkaline batteries (2300 mAh), this time by mounting the lamp head at a fixed distance from the wall and measuring the output at intervals with my Sekonic L-758DR light meter until it faded to non-usability. After a rapid drop by about 1/3 over the first 5 hours, the brightness decreased more gradually over the next 95 hours, at which point I quit. The light output still would have been adequate for following a well-maintained path or for reading in the tent. The light intensity curve approximated the shape of the performance curve shown on the Energizer website for their AA alkaline battery.
I also tested a set of Fry’s cheap alkalines, getting over 80 hours before I stopped the test. Again, the light level at the end of the test would have been adequate for a well-maintained path. I would expect the life to be longer using Energizer Ultimate Lithiums, which Energizer claims “lasts up to 9x longer” (3000mAh).
I did not test the Ultimate Lithiums for duration, since the price is rather high – I prefer to reserve these for an actual climb on a midnight approach. A difference with the lithium batteries is a very gradual drop for most of the battery’s life with a rapid drop at the end of life. I am a bit curious where the “9x longer” on the Ultimate Lithium packaging comes from – maybe compared to the old carbon batteries?
A question that arises concerns the statement in the BD instruction sheet that the headlamp runs on a power-regulated circuit. The statement reads:
“… the light output will be constant until the battery voltage reaches approximately 4.7 volts. It then transitions into a non-regulated system to extend battery life and maximize efficiency.”
I ran a test to check this with Energizer alkaline batteries, using my Sekonic L-758DR light meter to measure the intensity in a dark room. I found a decline similar to what I observed with the Eneloops for 20 hours, which transitioned to a fairly steady level adequate for hiking on a good trail for another 80+ hours, giving up at 102 hours total. An approximate calculation of the visibility distance (based on the 40 lux measured at 1 meter steady state) gave 13 meters at the steady level.
Repeating the test with a set of Fry’s bargain store-brand alkalines gave a similar result with 80 hours life. I then did a test reducing the brightness at the start to 150 lux at 1 meter, finding the intensity remained steady at the 150 lux (22 m visibility) for 25 hours (stopped the test at this point because I needed to use the headlamp for a real task, namely, we lost electric power for several hours – 2000 houses in the neighborhood, according to the city utility company).
I contacted Black Diamond Tech Support to find more detail on how the power regulation is supposed to work. I was told that, using Energizer alkalines, the brightness specification of 200 lumens should be constant for 3 hours, then step down to 150 lumens until the battery voltage dropped to some specified voltage, which the Tech Support person did not have at hand. At that point, the brightness would continue dropping until the brightness level at a 2 meter distance reaches 0.25 lux (1 lux at 1 meter).
With this information in hand, I inserted a fresh set of Energizer alkaline batteries (totaling 6.46 V) and placed the headlamp back on the stand at 1 meter from the wall. I took measurements every 15 minutes for the next 4 hours, then left the headlamp on, illuminating the wall in the dark room. To that point, the intensity had been dropping almost linearly with no indication of holding a constant level. Four hours later, I got up to measure the brightness, finding that the linear decrease had continued. Back to bed for a couple hours, then up again to find that the decrease had apparently stopped at 40 lux at a 1 meter distance, (giving a visibility distance of about 13 meters).
The graph below shows the light curve (intensity in lux on a proportional or log scale vs time) out to 80 hours. I finally turned the headlamp off at about 110 hours, at which point, the intensity was still high enough to hike on a good trail, well above the level at which I have returned to camp a few times through dense forest.
One difference in the test shown in the graph and the earlier tests was that, in the first few tests, I had started measuring only at 1 hour intervals, versus measuring at 15 minute intervals in the test shown. I was using a finer time resolution to see if I could see the power regulator steps. I was not using a continuously recording photometer (not having one available), so had to rely on the times I was available to take the readings.
Note that the tests spread over several days each time, up to 5 days of the lamp being turned on continuously. I am hoping for a clarification of why I did not see the described step-downs in brightness from Black Diamond. Since I observed no initial constant brightness period and no distinct step-downs, it is possible that the lamp I received for review was defective.
Regardless of that, the Icon performed extremely well for the kind of conditions for which I have use. Being usable for 4 or 5 days of continuous burning on a single set of batteries is impressive. Being bright enough for a lengthy pre-dawn approach (for 4 or 5 hours, for example) and still having enough battery life left for an all night return to base without having to change the batteries puts the Icon high on my recommended list.
Consider here that we have gotten along with much fainter headlamps for decades. For example, in 2011, I was climbing in the Cordillera Blanca, making all approaches in the 4-5 hours of pre-dawn darkness with my old 50 lumen Black Diamond Spot, or in the late 1990s, making approaches on the Mexican Volcanoes with an incandescent bulb headlamp that weighed far more, frequently having to make at least one battery change during the approach.
Using the headlamp at lower power will also extend battery life. With the Icon, you can set the brightness to a fainter, but still adequate level that is significantly brighter than the headlamps we used in the 1990s, and get along with a single battery set for a week’s of climbing approaches, or even running the all night leg of the Sierra 100 and similar adventure races.
In the instruction sheet, BD urges learning how to use the dimming feature properly to extend battery life. My suggestion is to set the brightness at the minimum level needed for the approach and reserve maximum brightness for those times when it is really needed — such as during route finding during the technical parts of a climb, skiing rapidly when returning to camp after dark, or when running a night orienteering course or long adventure race like the Sierra 100.
Low Temperatures: If batteries are exposed to very low temperatures during use, battery life, even with lithiums, will be significantly shortened. At this point, I have not tested the Icon in low temperatures (that’s why this is a preliminary report). I expect that the battery case being in a pouch with shoulder and belt straps will allow carrying the batteries under my outer layers to keep them warm in really cold conditions. The cable between the battery pack and the headlamp itself connects with a very solid screw-on connector, as seen in the image of the battery pack earlier in this review. Since you would normally wear the case inside your warm layers, switching clothing layers can sometimes be a little awkward.
One worry with carrying the battery case remotely is whether it would bounce annoyingly during a running event, such as a 24 hour rogaine, or even during normal hiking. The combination of a shoulder strap plus a belt, both of which are adjustable avoids the bounce problem. I did not find any problem with the battery case bouncing or swinging whether hiking normally or running off-trail, whether inside my layers or outside.
Swapping batteries in the BD battery case is simple and fast, though I found turning the lock lever on the battery case sometimes had the locking cam misaligned with the slots. Being able to carry the battery pack inside your parka solves the temperature problem to a large extent. Still, it is a good idea to carry 1 or more extra complete sets of batteries (4 in a set).
Night Hiking: After doing the preliminary tests, I headed out on the trail to do some short night hikes and an extensive night hike, plus an off-trail simulation of a night orienteering run. One of the problems I quickly discovered was that the brighter levels of the Icon Polar’s QuadPower LED are way too bright for busy trails (same problem as when I tested the Petzl NAO on the same trails at night). Oncoming hikers would stop and turn their backs, cover their eyes, and otherwise just stop hiking until I was past. In one case, one hiker literally threatened to rip the headlamp off my head, despite my aiming the headlamp downward and to the side of the trail. I would highly recommend using the headlamp at reduced levels on heavily used trails at night, perhaps only with the SinglePower pair turned on.
I took the steep, rocky shortcut for the last 250 meters or so to the summit of Mission Peak, to simulate a third class scramble. The brightness and beam spread at the brighter levels over the broken rocks was much appreciated. I was aware, though, of the limitation of headlamps that they provide “flat lighting”, which hides the contours of the land somewhat. The way around this (along with the backscatter of fog) is to wear the lamp head at waist-level or on your thigh, to give oblique lighting and provide some modeling of the terrain.
The extended hike itself (shown on the map below and in the profile following) was 5.9 miles, car to car, with a gain of 2100 feet (yes, I know that the diagram shows 2190 ft, but that is because the GPSR I was using adds up the errors in elevation and does not smooth the variations out – setting the recording interval from the default 2 seconds to something like 30 seconds would give a more accurate result, though the measured altitudes at each recorded point are quite accurate).
At the summit of Mission Peak, I stood on the true summit and shown the Icon over at the observation pole that most people think is the summit. I measured the distance using my Leica Distal laser tape at 127 feet (38.5 meters). I photographed the lit area with the camera set at 1 second, f/3.5, ISO 1000. The night was partly cloudy, with no moon. The lights of the San Francisco Bay provide a background, with San Francisco itself at the right (north) side of the photo and San Jose to the left. The image is pretty much as the eye sees it.
The Black Diamond specification of the lit distance is just over 100 meters at the maximum 200 lumen brightness of the QuadPower LED. On the way up and down, there were places where it was obvious that objects up to 100 meters away were visible. If you compare this photo with the similar one in my Petzl NAO review, you will note that I was positioned some 70 feet closer, but with a similar light coverage.
On the down-climb, at several points, I spotted pairs of bright points, eyes of some animals peering at me. Since there are lion, bobcat, and coyote in Mission Peak Park, it does make one nervous to see two eyes staring back at you in the dark. As it turned out, these were Black Angus cattle, which are allowed to graze in the parks (to keep the grass down and reduce fire danger). Still, their eyes were very visible at over 100 meters away (I walked right up to them and had to detour from side to side of the trail, since the cows themselves were almost invisible until I was right on them).
I completed the 5.9 mile round trip in 2h46m. During that time, there was no noticeable dimming of the lamp. You can check the battery level when turning the headlamp on by looking at the indicator LED on the side of the lamphead, though there are only 3 levels shown (green for >75%, orange for 25-75%, and red for >25% remaining)
The lamp color is sufficiently like daylight to render the colors on a USGS or orienteering map recognizable. The QuadPower LED is powerful enough to impair your night vision. So you should switch to the single-power LED pair for map reading or at least use the power switch to reduce the intensity. The red LEDs do not affect your night vision, but the red light distorts the colors on the map, a serious problem when orienteering.
The Icon Polar is an excellent choice for a wide variety of outdoor activities, not just for extreme cold. It appears to be sufficiently rugged for heavy use in active activities like backpacking, mountaineering, rock climbing, and ice climbing, as well as those times when you have to spend time in a bivouac or holed up in a tent of snow cave waiting out a storm. The stiff price is typical of the most recent high-powered headlamps, but the performance and versatility seems well worth it.
Finally, did the Icon Polar meet the 8 criteria I gave at the start? My personal answer is “yes” to the all eight. Whether you, the reader can answer the eighth question in the affirmative depends on your activity and level of involvement with the activity is.
In short, I would recommend that anyone engaged in outdoor activities involving nighttime activity at subfreezing temperatures give serious consideration to the Icon Polar.
Follow-up subzero testing:
During March 2013, I went to interior Alaska to spend some time dogsledding in the Alaska Bush. This involved a week mushing along the frozen Yukon River and several tributaries, as well as through forested areas. We covered over 100 miles, staying in tents and remote cabins. During the nights, temperatures got down to as low as -30°F. As expected, the Icon Polar gave full brightness when I wore the battery pack under my layers, but when the batteries were "chilled" by leaving them out overnight, the battery power dropped significantly, with shortened battery life, despite using Energizer Ultimate Lithiums. Energizer gives the operating range for the AA Ultimate Lithiums as -40 to +140°F. Based on my experience, I would estimate the battery life to be about 8-10 hours in the -30°F unprotected environment when turned on at full power (regular alkalines can die within a couple hours in those conditions), compared to the 100+ hours I measured at "room temperature". There is some fall-off in brightness with time, of course, but the light after chilling for most of the night was still enough for walking around in the pre-dawn darkness. Using reduced power would prolong battery life at cold temperatures if necessary without having the capability of the pouch to keep the batteries inside your layers. Wearing the pouch at your base layer and under all insulating and windproof layers provides the best warmth and hence best battery lifetime. Using handwarmer packets attached to the pouch will also help.
Been using the 200 lumens edition. Great balance between…
Source: bought it new
Price Paid: $80 cdn
Been using the 200 lumens edition. Great balance between battery life and brightness. Headlamp is best for usage in cold weather—even during the spring and fall. Unless one is needing a floodlamp to light up the whole woods, this will do for most every backpacker.
- Great illumination
- Sturdy design
- Separate battery pack
- Cycling through the modes
- Red light is bright although dimmable
I've been using the 200 lumens edition. I got it originally because I was tired of all other types of lights being either dim and having a low battery life or bright with no battery life. I would highly recommend this headlamp.
The separate battery lamp really helps with cold weather as the cold will drain your AA batteries even when there's no snow (cold nights). It practically reaches as far as a car's headlights on the road, but obviously won't create that amount of illumination. However, it is quite bright and will doubtlessly illuminate your surroundings.
The highly annoying thing about it is that if one wants to use just the spot for moments when needed one has to constantly cycle between flood lighting and spot lighting. If they could enable one just to keep one mode at a time, that would be great.
On minor notes, the red light is still pretty bright. My sleeping friends got annoyed about its brightness. Just a quick note, the paragraph makes it sound like it's really bright, but it is not the brightest thing on the market. What is impressive is its battery life in comparison with its brightness.
The headlamp can be "locked" in a manner to keep it from turning on accidentally.
The headlamp is rated to last 25 hours on new batteries, but I find that it actually is bright for less. I'm not sure when it begins to fade to the point of un-usability (since I haven't run it for 25 hours straight).