Written by Andrew Easom Bentley - http://outdoorkinetics.co.uk

Petzl NAO 2 575 Lumen Head Torch Review

A couple of weeks ago, I posted a review of the AP Pro Series 100 Lumen Head torch which packs a lot of punch for it’s £25 price tag but unfortunately it didn’t really work too well for trail running. Today I’m going to be looking at a model from the other end of the price spectrum, the £145 Petzl NAO 2 which updates the original version of the torch for 2014 with a max output of 575 Lumens.


  • Reactive lighting with variable power from 7 to 575 Lumens
  • Two pre-set reactive lighting power settings. One for max power and another for max autonomy (optimised battery life)
  • Two further pre-set constant power settings
  • Ability to customise lighting settings by downloading Petzl’s ‘OS’ application and connecting the torch to your computer
  • Battery life of up to 12.5 hrs, depending on settings (see table below for more info)
  • 20 Lumen ‘Reserve mode’ providing 1 hour of burn time in the event that battery level becomes critical
  • Power provided by a lithium Ion rechargeable battery with the option to use two standard AAA batteries in an emergency (with reduced performance)
  • Rechargeable via USB port (including phone chargers, car cigarette lighter adaptors, computers etc)
  • Optional belt clip and extension cable for battery
  • Replacement batteries available at around £40
  • Adjustable fit with draw cord head harness
  • Battery level indicator lights
  • Charge time of 5 hours
  • Tilt-adjustable light unit
  • Water resistant to IPX4
  • Weight of 187 grams

    Reactive Lighting Explained (hopefully….)

    It seems as though there has been a big increase in the number of head torches on the market that are targeted at trail runners and this has lead to an inevitable increase in power, as everybody wants to have the biggest and the baddest model. A potential down side to this is a reduction in battery life OR an increase in battery size and weight to compensate. Pezl have sought to overcome this with their ‘reactive lighting technology’.

    The NAO features a clever sensor which detects the amount of light that is reflected off of objects in the torches path and automatically regulates it between 7 to 575 lumens so that (in principle) you have loads of power when you need it and just a little bit when you don’t. This is intended to improve the battery life, reduce the amount of faffing about that you need to do with the settings and prevent you from being temporarily blinded by reflected light if you look down at a map etc. This concept is most easily understood if you take a look at


    The table below is lifted straight from the Petzl website with a couple of minor edits to hopefully illustrate how the lamp performs at the different factory pre-sets. These can all be customised via the Petzl OS application

    Lighting Technology Lighting Modes Brightness Distance Burn Time Reserve Mode
    REACTIVE LIGHTING Max Autonomy 7 to 290 lm 2 to 80 m Around 12 h 30 1 h at 20 lm
    Max Power 7 to 575 lm 2 to 135 m Around 6 h 30
    CONSTANT LIGHTING Low Power 120 lm 60 m 8 h
    High Power 430 lm 130 m 1 h 30

    First Impressions & Thoughts on Design

    Petzl have been producing high quality, performance headlamps for a long time and they know their onions. It therefore comes as no surprise that the NAO is a well constructed piece of kit with impressive build quality.

    The headband is adjustable via an ingeniously simple draw cord system that works really nicely so it is easy to customise the fit and ensure that the unit sits securely on your head. Unfortunately, the NAO lacks any padding between the lighting unit and your forehead (apart from a thin strap). This is a common bugbear of mine and I’d prefer to see a thin section of foam to provide a little bit of cushioning as even the best fitting torch can begin to dig into your head after a while and become uncomfortable.

    Petzl have been able to cram a lot of power into a small battery and the unit feels surprisingly light as a result. The battery comes with a set of three lights to indicate the power level which is a great feature but you have to take the lamp off to check it. I don’t see this as a flaw because some units don’t have battery indicators at all but I think an audible alarm indicating say 75%, 50%, 25% power would be another useful addition for future models, especially for ultra running (although I’d also want the option to turn it off!).

    The method of battery release is one thing that does bug me about the NAO as it requires you to press a fiddly and fragile looking clip with your finger tips which can be frustrating if you are rushing and difficult with cold, numb hands. This isn’t a major issue but I found it surprising, given the technology and attention to detail that has gone into the rest of the design.The lamp is turned on and off via a rotating knob on the side of the unit that allows you to scroll between the settings. This is a really great piece of design and is much easier to operate than annoying little buttons when you are on the move or wearing gloves. It also has a ‘lock’ setting to stop the light from turning-on by accident during storage. Most torches quote a simple estimated battery life at a fixed output level. Things are a bit more complex as this with the NAO as the actual battery life you get will be dependant on a high number of variables. For example, if you tilt the light so that it is pointing out in the distance, the unit will switch to high power and consume the battery quickly whereas if you are running next to a partner and they have their torch pointing at the ground in front of you next to yours, the NAO will drop the power and the battery consumption is reduced. This concept is actually pretty easy to understand when you use the torch – the brighter the beam, the quicker it’s using the battery. To be honest, I haven’t timed the battery life at the different light levels to verify if the Petzl figures are correct but I’ve seen nothing to indicate that they are too far off of the mark based upon a few weeks of regular use. 


    The NAO provides a comfortable fit that remains secure, even if you are landing with heavy foot falls when running quickly down steep descents. It comes with an optional additional strap to go over the top of your head but I haven’t found that I’ve needed to use it. The lamp unit does bob around a tiny bit if you are really pushing it on rough ground but this is hardly noticeable and the overall stability is much better than many units that are out there.

    Brightness levels are really very impressive indeed, especially at the upper end of the torches power range. I have used other units that claim higher outputs of up to 1000 lumens but I personally think that this starts to get overkill for running and the 575 Lumen NAO offers more than enough for every situation you are likely to encounter, even whilst moving quickly on the steepest most technical terrain. The torch has two lamp units, one which provides a diffuse beam to illuminate object that are relatively close by and another more focussed beam for looking further into the distance (i.e. route finding). The reactive lighting technology switches between the two depending on feedback from the sensor and I think Petzl are right on the money with the light distribution levels provided by the two beams.

    90% of the time, the reactive lighting works in a completely unobtrusive manner as it seamlessly adjusts the power levels to provide the optimum level of illumination. Quite often, you don’t even notice that it’s happening (in a good way) and you can pretty much leave it to do it’s own thing. As well as preventing you from being blinded by reflective light if you look at an object close up, it also provides a bit of a safety feature if you accidentally shine the beam in someones face or look at an oncoming car that has it’s headlights on as it will reduce the brightness (although this is obviously still unpleasant for the victims).

    There are occasional circumstances where the reactive lighting doesn’t perform quite how you would like and the brightness is reduced unexpectedly. The sensor can become confused by things like fog, breath-mist or reflective material on other runner’s clothing. I’ve come across a couple of instances where other reviewers have been quite critical of the original NAO for this but to me this makes no sense whatsoever because in these circumstances, you can simply switch from reactive lighting to constant lighting in an instant and the NAO will work just like a regular high-performance head torch.

    I’ve also noticed that some people have come down quite hard on the NAO’s battery life. Yes, on the face of it, 1.5hrs at a constant 430 Lumens doesn’t sound that great but in reality, you are never going to need to use it that way and when you consider the weight of the unit and the fact that there is almost endless scope to customise the settings to provide the battery life you need, I just don’t see this as a major concern. Spare batteries are quite expensive however at £40 and I think it would be great if Petzl produced an optional larger model that works with the belt clip for extra long excursions.


    The Petzl NAO 2 offers fantastic performance and innovative technology that has been well executed. You can tell that it has been developed and tested by people who really understand how their customers are going to be using the lamp and have come up with a near-perfect design. Whilst £145 is a lot of dosh for a headlamp, you can see where this money has been spent and I think it’s pretty good value at the price (better still if you can find one for less!)

    I’ve been using the NAO regularly for the last few weeks and will continue to do so throughout the winter. I’m interested to see how the reactive lighting performs in a wider range of conditions and will update this post over the coming months to report back but I’m really impressed so far!

    This product was provided as a test sample by the manufacturer, please refer to my gear review and advertising policy for more information.

    Where to Find One

    The Petzl NAO 2 575 Lumen can be purchased at Wiggle and Amazon.

    I make every effort to ensure these reviews are as objective and honest as possible to help you decide if a product is right for you. This takes me a lot of time and effort and if you are interested in a product I have reviewed, you can help me keep the site going by placing purchases through the links and adverts at no extra cost to yourself. Thanks for your support.