Earlier this year Petzl introduced the Nao headtorch with 'reactive lighting' technology. A new direction in the evolution of head torches, it has a built in light sensor that can automatically adjust the beam and light output to suit the conditions. As Mick Ryan reported from Outdoor Retailer Show in Salt Lake City, Utah, where the Nao was launched: "If you are reading a map it switches to proximity lighting - beam is wide and less powerful - if you are descending a ridge it will automatically switch from proximity lighting to distance lighting - beam is more focussed and powerful; depending on where you turn your head. So rather than you switching to different light modes the Petzl Nao does it for you allowing you to concentrate on the task at hand and at the same time conserving power."
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In 1981 Petzl introduced an innovative headtorch designed for outdoor activities. The Petzl Zoom was, by today's standards, about as simple as it could be. Elastic straps (reputed to be knicker elastic from the local market) held it on the head while at one end there was a battery case and a bulb unit at the other. The power came from a strange block battery that was fastened in place with push on clips and the bulb unit could be twisted to create a spot or flood beam. It was an industry leading product and soon became the 'must have' torch for alpinists and winter climbers.
Petzl had produced a great product but they didn't sit still. Soon the Zoom had a halogen bulb option and the battery could be replaced by a holder for AA batteries. Helmet clips could be added to hook it on securely and it wasn't long before other models with combined bulb and battery units were added. Programmable models, LED units, rechargeable batteries and many other innovations have followed in the intervening years and Petzl have always been there pushing the boundaries. Now they appear to have done it again – Petzl Reactive Lighting is here...
At first glance the Nao looks like most headtorches. A lighting unit at the front, a battery pack at the back, a cable to link them and elastic straps to fasten it to your head. However, closer inspection reveals several key differences to any other model currently on the market.
Firstly, the lighting unit features two side by side LEDs but then a sensor sits above. The sensor, which is a key feature of the Nao's reactive lighting technology, measures incoming light and adjusts the headlamp output accordingly.
"Petzl have always been there pushing the boundaries. Now they appear to have done it again – Petzl Reactive Lighting is here..."
On the right of the lighting unit sits a large square on/off switch to click through the lighting functions.The battery unit, which sits at the back of the head, contains a rechargeable cell housed in a plastic casing. Above these is a USB connector which, in normal use, is housed in a sealed plastic cover but then pops down to allow recharging or to link the Nao to a computer to utilise the Petzl OS software (more about this later). On the housing there is also a battery monitor showing the remaining charge level.
The strap system that holds the Nao on the head is a mixture of tried and tested and new. There are strips of elastic running along each side that are similar to many headtorches while a less typical drawcord system completes the attachment. The final link is a curly cable connecting the head unit to the battery.
I've only had the Nao for a few weeks and getting a headtorch to review in the middle of summer (and with a tight deadline) is never going to make the job easy! So far it has been used on a night navigation session (where participants had a variety of head torches so it was interesting to draw some comparisons on brightness), a camping trip on the Gower Peninsula and another camping week in the Lakes, some night running sessions and a couple of off road MTB rides around the Peak District. The final tests have been various little investigations at home (such as putting it in water, using chunky gloves and trying different charging methods). I am very aware this hasn't allowed tests in a full range of use and doesn't allow any assessment of longer term durability.
The Nao is, in reality, 2 types of headtorch (with reactive lighting or with constant regulated output) so it seems easiest to split the review into 2 parts.
As a conventional headtorch the Nao works really well. There are 2 light outputs available in the, what Petzl refer to as, constant mode (once the Petzl OS software becomes available in July this will be programmable but more about Petzl OS later). These 2 settings offer either 315 lumens output giving a distance range of about 98 metres or an 88 lumens output giving a 48 metre range. The output is regulated which means the output stays constant until the battery level reduces to the point where the regulated output can't be maintained. At this point output will fall to a level suitable only for close range operations. Petzl acknowledge that battery life is partly dictated by factors such as temperature and use profile but the expected battery life in high level output is given as 100 minutes and up to 8 hours for the lower output mode.
"The high output mode is very very bright. During a night run this amount of light was fantastic (in fact it made it feel more like a day run!)"
The high output mode is very very bright. I was able to pick out distant features and during a night run this amount of light was fantastic (in fact it made it feel more like a day run!). Apparently the original Petzl Zoom was around 25 lumens so it's amazing how far things have moved on. The obvious sacrifice is, of course, battery life. 1 hour 20 minutes may be fine for a run (well it certainly is for the distances I can run!) but won't be anywhere near enough for winter mountaineering or alpine use. Having said that users are rarely going to need that much light constantly - 315 lumens suits that brief time when a route needs to be picked out or a footpath spotted but for most of the time 88 lumens will be plenty and then the battery life becomes far more realistic. What isn't clear is how varying use between these 2 will affect the expected burn time but, in reality, I suppose this is so variable from use to use that it's probably impossible to give very accurate calculations.
On the top of the battery unit there's a battery monitor that helps keep track of battery life. The indication is given by 3 LED's that show levels at less than 33%, between 33 and 66% and then between 66 and 100%. There's one final indication when the last LED starts to flash – at this point the battery is in reserve mode and the Petzl manual says there is 30 minutes remaining.
Charging the battery is via a 5V USB charger. The USB connector can be plugged straight into a computer (a lead is also supplied to help with this link). Petzl also produce an optional mains or cigarette lighter charger. I was disappointed that, on a torch costing this much, a mains charger wasn't provided as part of the package. I usually want to charge things through the mains and on a Petzl Tikka XP2 (with Core battery) that cost far less a handy little mains charger was included when I bought it last year so I wish Petzl had done the same with this one? It is a fairly standard charger that comes with various devices so they are easy to come by though.
"You can fine tune brightness, burn time and distance settings as well as storing 4 activity profiles, 10 customised lighting levels and create and share custom activity profiles"
The Nao's pre-programmed settings are designed as 'multi-activity' and will probably suit most users. In July there will be Petzl software (available as a free download) which allows different profiles to be utilised. The instructions for the Nao say users will be able to fine tune brightness, burn time and distance settings as well as storing 4 activity profiles, 10 customised lighting levels and create and share custom activity profiles. Phew! I have a similar facility that came with my XP2 and, in all honesty, I've only tried it once although that's more to do with the fact that I've been happy with the profiles that came with the torch. I'm sure there will be plenty of users who make much more use of these features.
In general use the operation of the Nao has been great. In my opinion a big drawback of recent Petzl models was the fiddly rubber switches that make it hard to operate the torch with gloves on. On the Nao there is a large square knob that makes it so much easier. A turn clockwise will scroll through the reactive modes and holding the switch for a couple of seconds will activate the constant lighting modes. I haven't had a chance to see how effective this is in a blizzard on Ben Nevis yet but I have tried it with a selection of my thickest winter gloves and it worked really well. It's in the right place, it is the right shape and the modes are pretty intuitive. With the little rubber buttons on previous models it was also conceivable (although it never happened to me) for the torch to get turned on as it nudged against something in a rucksack. On the Nao the locking system is much more secure. The on/off knob needs to be turned through 180 degrees and it then locks with a reassuring click. It is worth noting that it can be locked while the torch is still turned on. I can't see why anyone would want to do this in normal use but it is possible to foresee a user locking the torch (thinking they were also turning it off) while it is still on and consequently discharging the battery.
The Nao uses a 2300 mAh rechargeable Li-Ion battery which is purpose made for the headtorch. The literature says that after 300 recharge cycles the battery will still have about 70% of its initial capacity. Spare batteries are also available. I had never used rechargeables in a torch until I started using a Petzl Core battery last year and it soon showed some big advantages over alkaline or lithium batteries. In winter I charge the battery the night before heading out and then I always know I have a full charge. Prior to that I had to either put a new set in or try to estimate what burn time was left. There are also environmental and cost advantages of using rechargeables. Although the torch may cost more that expense will soon be recouped if used often enough. For example, I worked out once that the Core battery costs about the same as 10 packs of decent quality AAA alkaline's.
One big disadvantage of rechargeables is if they can't be replaced 'in the field' (unless you carry a spare). Even with a full charge I always carry a spare set of batteries with me. Fortunately, in the Nao the battery can be replaced with 2 AAA lithium or alkaline batteries if need be (not Ni-MH or Ni-Cd rechargeables though). Petzl say this is just for emergency use and will provide non-regulated lighting and the lamp performance is reduced. In reality these replacement batteries are quite fiddly to fit and I certainly wouldn't fancy doing this in a blizzard.
"Swapping the battery mid use is unlikely but if it does need to be done in challenging conditions it could be tricky"
Linked to this is the usability of the other parts of the casing. The Nao is, due to its many features, quite complicated. The head unit is fully enclosed and the switch looks and feels robust so hopefully there won't be any problems there. The battery casing, however, certainly has more vulnerable bits. It has a removable cover that snaps into place. This works well but is not attached and opens outwards. Trying to do this in challenging conditions or with thick gloves on would be difficult and I could certainly envisage the cover getting lost.The old Zoom, for all its simplicity, had a lid that lifted up and was permanently attached so it could never be lost. Hopefully, given that users can always head out with the Nao battery fully charged, swapping the battery mid use is unlikely but if it does need to be done in challenging conditions it could be tricky.
The USB connection sits at the top of the battery pack and tucks into a clear plastic cover during use. When users need to access it a clip on the battery cover allows it to swing round. This works well and, as the USB is only likely to be accessed in the comfort of a building, should be fine.
The final link is an attachment point on the cable that allows the battery unit to be completely detached. Petzl sell an optional extension lead that then allows the battery to be stored in a pocket or rucksack. This may suit people using the headtorch in very cold conditions or runners who find the battery unit too heavy. The potential problem is that it's another link that could cause a connection problem. The connector slots into place then turns to lock so it certainly seems robust enough and I can't comment on its long term durability.
The other thing about any openings and connectors is their vulnerable to water getting in. On the Nao any vulnerable points have a rubber seal and the headtorch is rated as IPX4 (many Petzl torches are rated to IPX4). This means it is water resistant and will cope with the harshest weather conditions. It also means, because of the stainless steel contacts and waterproofing of key components, that it will work if water enters the housing. I haven't had chance to use the Nao in harsh weather conditions but I did submerge the torch in a bowl of water and left it for 30 minutes. It worked quite happily during that time and, when it was inspected afterwards, no water had entered the battery or USB housing and I could see no signs of water having got into the lamp unit.
The main innovation of the Petzl Nao is the reactive lighting system. The sensor in the lamp unit detects the proximity of objects and adjusts the light output accordingly. It's a idea but one that, I've no doubt, has a lot of incredible technology behind it. In use the change in intensity is instant and all the user will be aware of is getting the right amount of light at the right time.
The reactive lighting system has 2 settings similar to the constant profiles. At high output this is a whopping 355 lumens of output (which the reactive lighting system will reduce anywhere down to 7 lumens as required) or 98 lumens on the second setting (which will again reduce as required down to 7 lumens). This means the high output gives a whacking maximum beam length of 108 (reducing down to 9 metres as required) or 55 metres (again reducing to 9 metres) for the lower setting.
"The advantage is most noticeable during fast moving activities like running and biking or activities that regularly switch between near and far distance like night navigation"
As well as ensuring the right amount of light this also means the Nao is only using the lowest amount of battery power for the required output. This should significantly increase battery life although, because every use profile will vary, it is very hard for Petzl to say by how much. The information provided states that lab tests have demonstrated a range between 100 minutes and 50 hours although an average of around 4 hrs 40 minutes for the higher output level and 8 hours for the lower power level setting is suggested. Petzl point out that the angle of the lamp unit is also important. If it is angled more horizontally it will be sensing further away more of the time but if pointed slightly downwards then battery life will be improved.
So how does it perform?
Easy - the Nao reactive lighting system is brilliant! It effortlessly does what it's designed to do. The advantage is most noticeable during fast moving activities like running and biking or activities that regularly switch between near and far distance like night navigation. Running through wooded ground is a doddle as the route gets lit when needed but the runner doesn't get dazzled when looking at nearer ground. Although biking at speed tests it even more the Nao again copes easily. When navigating at night the change in brightness really helps when moving from close up viewing of the map to looking at the ground ahead.
So it's great ... mostly. I've had absolutely no problems but I have heard anecdotal evidence of a few situations where the reactive lighting sensor may struggle to cope. Firstly, when the Nao looks at highly reflective surfaces it can reflect the light back and change the intensity. When the user then looks away the light adjusts until turned back to the reflective surface and this can apparently create a bit of a strobe effect. The same can apparently happen when the sensor looks at bright lights (like car lights) although I didn't find this a problem.
I was told this might also happen in very heavy rain or snow but it can actually be a help rather than a hindrance. I heard of an adventure racing team that were out in horrendous conditions and the Nao proved to be a great option as it adjusted the light to a lower level in the reflective conditions and avoided dazzling the users whereas the 'traditional' torches had to be continually adjusted. I tried to recreate this with a hosepipe but couldn't get it to happen even with a simulated heavy rain shower. In reality none of these are ever going to be a big problem because the reactive lighting can always be over ridden if conditions require it.
I've also found that the cord head cradle can get tangled but this is easily solved by always fully retracting the drawcord for storage. Of course, having to cinch the drawcord means the head cradle can't be left set to a certain size but the adjustment is simple enough. Having said that, I would have thought Petzl could provide a storage container for this torch given the price? Fastening the headtorch on to a bike helmet is quite tricky but I used some of Petzl's clips that are designed for broad rimmed helmets and they worked fine.
The Nao is quite a big package (187 grams with rechargeable battery) but it's a very bright torch so the power to weight ratio is actually very good. The models I've been using recently (that I've used as benchmarks) are the Petzl RXP and Tikka XP2 Core. The Core, by comparison, onlyweighs 88 grams (including rechargeable battery) and it's a very small package. They are certainly very different and the Nao is many times brighter but the truth is the Tikka XP2 has done everything I've needed and costs far less so the Nao is by no means a 'must have'.
The battery system also limits the uses of the Nao. For days out and shorter camping trips it will be fine but for expedition use or long term trips it is less practical unless a reliable charging system is available. With something like the Tikka XP2 the rechargeable battery can be left at home and AAA's used as a direct replacement so longer trips are no problem whereas in the Nao the AAA's are only recommended as emergency back-up (not sure why they are classed as emergency use though?).
The Petzl Nao is a brilliant innovation and the proximity lighting system works superbly. It also functions really well as a standard regulated headtorch.It does have limitations and it suits certain uses but, if it suits the user, it does exactly what it is designed to do. At £135 it is very expensive although the cost is reflected in the fact that it's a technologically advanced product that has a lot of features. Some of the outlay will also be recouped by the rechargeable battery.
"For things like night time biking, running, night navigation, alpine ascents from a valley base or standard mountaineering uses where I can easily recharge it – then from now on it will be my very top choice."
I have also long felt that some products that sometimes just need to work and in difficult conditions headtorches are one of those things. By my reasoning, as the features increase there is potentially more to go wrong. I've certainly had no reliability issues with the Nao but there are undoubtedly a lot of components in there. For expedition use or as a back-up headtorch to keep in my rucksack the Nao won't get a look in. For things like night time biking, running, night navigation, alpine ascents from a valley base or standard mountaineering uses where I can easily recharge it – then from now on it will be my very top choice.
Paul Lewis is the owner of mountain adventure and training specialists Peak Mountaineering. Paul offers a 15% discount on all courses for UKC users.
Find out more at peakmountaineering.com or contact Paul on 01433 620283.
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