Black Diamond Iota Headtorch Review

© Martin McKenna

Weighing only 56g, yet maxing out at 150 lumens, the Iota's impressive power:weight ratio makes it a great backup torch. But it also has everyday uses, says Hugh Simons.

Black Diamond's well-named Iota is a tiny yet impressively bright headtorch with a built in Lithium Ion battery for convenient charging. As one of the lightest headtorches currently available anywhere (and the lightest BD offer), this has the credentials of a seriously versatile little light source, with uses ranging from emergency backup to simple car camping, after work runs to winter walking... and even climbing. So how does it fare in use?

The Iota in use descending off a climb on the Shelterstone  © Martin McKenna
The Iota in use descending off a climb on the Shelterstone
© Martin McKenna

This headtorch is amazingly small and light – held in the palm of the hand or attached to a climbing helmet, the weight is barely noticeable. With a built in, micro USB charged Lithium Ion battery which can supply a max power of 150 lumens, and a single button operation, the Iota is both minimalist and simple to operate. Yes it has limitations - most obviously the limited burn time (2-3 hours on full power), but for its size, weight and cost I think it's a brilliant choice for those wanting a super lightweight torch for a broad range of activities, from emergency backup to more general use in some situations.

Fit and Weight

Black Diamond gives the Iota a weight of 56g, which is incredibly light. For its power rating, I could not find a lighter headtorch anywhere on the market. When on my head, it sits comfortably. Since the Iota is so light, it is barely noticeable, and the adjustable elastic strap keeps it in position well. When attached to my helmet, I genuinely cannot tell it is there – this is something I've not experienced with climbing with a head torch before. The strap is big enough for it to easily stretch to fit on to helmet mountings. The fact that the light unit itself is so small also means that it does not get in the way when squeezing through tight gaps and when walking or running, it doesn't move or bounce up and down due to its weight. I could happily wear this torch all day long!

The strap is easily adjustable and very comfy  © Liam Watson
The strap is easily adjustable and very comfy
© Liam Watson

Modes and Output

The Iota has three main modes: High, Dimming and flash. It doesn't have a red light setting. The burn times quoted from Black Diamond are as follows:

  • Low – 40 hours
  • Dimming (Average) – 22 hours
  • High – 2 hours

The max distance you can see on the highest setting (150 Lumens) is 40m. On low power this is reduced to 7m. Compared to the BD range as a whole, the Iota's range fits into the lower end of the spectrum. In practice, I found the beam nice and even (not too directional) which lights up plenty of path in front. It was of course limited when trying to see further ahead, but 40m range is more than sufficient for most applications that I would use this head torch in. If I was approaching a new crag in the pitch black or on an exposed ridge with tricky terrain in the night and wanted more reassurance that I could see as far as possible and I'd probably switch up this torch for a more powerful one. When camping with this torch, I stick it on its lowest brightness setting and can happily illuminate a whole tent whilst not using much battery power at all.

Quite an in-tents beam, even on minimum power  © Hugh Simons
Quite an in-tents beam, even on minimum power
© Hugh Simons

Unless I knew I was going to be on easy terrain (e.g. a landrover track) for an extended period of time, I would usually always have the Iota on maximum brightness; I find that 150 Lumens is never too bright for walking and seeing the path ahead. This does have the drawback that you are at risk of running your torch low over a full night of activity. Given its size though, this drawback is to be expected.


The power source is a built in Lithium Ion rechargeable battery. It is charged by micro-USB (cable supplied with the torch). Because of the abundance of USB chargers these days, I much prefer this method of charging over traditional AA or AAA batteries. Portable battery packs are pretty commonplace now as well as cheap, and so charging the Iota on multi day trips is no problem. It is really handy to be able to charge your torch on the drive North using your car's 12V socket – one less thing to worry about beforehand! Timing wise, charging takes a couple of hours, although I've never charged the Iota from completely flat to full charge. Black Diamond quote a charging time of three hours, which seems reasonable to me. Hopefully the next generation of USB charged headtorches upgrade to USB-C for even faster charging times!

Micro-USB charging – easy with a battery pack  © Hugh Simons
Micro-USB charging – easy with a battery pack
© Hugh Simons

As mentioned, the battery is sealed into the torch, and as such replacement batteries are not available. This does limit the versatility of the Iota somewhat; if you were out all night using the torch on full power you would run out of charge after a few hours and not be able to replace or replenish the battery. However, I think its core use is not as extreme as this – after work runs, approaches to climbs, camping, emergency torch etc are all more suited to the Iota's battery life.

The Iota carries a IPX4 rating, which roughly translates as 'water resistant', i.e. it will still work if it starts raining but if subject to any serious jets of water it may begin to leak. I would say this is perfectly acceptable for a torch of this kind, and it is well protected from the elements in a mountain setting.

The 'real life' battery life that I've experienced so far has been very encouraging. I easily got three hours use at full power whilst on a walk in and out of a winter route in Bidean Nam Bian in Glencoe. It was hard to tell by the end of the day if the output was dimming slightly; I expect it was a bit but it was definitely not a big issue and I managed to get back to the car with plenty of battery life left. The torch spent all day attached to my helmet and as such was exposed to cold temperatures – typically cold temperatures sap the battery life, but the Iota held up well to this.

You can also do it in your car en route to the hills  © Hugh Simons
You can also do it in your car en route to the hills
© Hugh Simons


A single tap of the switch on the Iota turns the torch on with the default being the dimming mode at its brightest setting. A double tap of the power button boosts it to the max brightness while a press and hold activates the dimming function. I found that sometimes if the double tap is too quick nothing happens and if it's too slow then it switches to the dimming mode, which is a little annoying and takes a bit of getting used to.

To get the Iota on flashing mode, you press the button 3 times.

The Iota has a handy system for telling you how much battery you have left. A tiny LED on the side will illuminate for about 3 seconds when you turn the torch on – depending on the colour this will tell you how much battery you have left. If the LED shows green then you have more than half the battery life remaining, if the LED shows orange then you have between 25% and 50% battery life remaining and if it's red then you have less than 25%. This is a neat little feature, demonstrating a well thought out design.

Camping is an ideal use  © Hugh Simons
Camping is an ideal use
© Hugh Simons

This torch also features a 'brightness memory' function, which - you guessed it - remembers which brightness you had when you last used torch. This could be particularly useful when you are camping, for example, where you might want to use the torch on a dimmer setting and don't have to keep adjusting it every time you switch it on. It is activated by pressing and holding the button whilst on the desired brightness setting until it flashes blue, then keep holding the button down until it flashes yellow. It is deactivated in the same way.

The final operational feature of the Iota is the lock function. This is activated and deactivated by pressing and holding the button for approximately 4 seconds. The small LED on the side flashes blue to indicate it is locked once you have held the button for 4 seconds. While this is undoubtedly a useful feature (headtorches switching themselves on in your bag is a massive pain!), I have never actually used it so far. I find the torch small and compact enough and the button suitably stiff that I have not had any problems with it switching on in my bag so far. This is perhaps because I have never owned a headtorch with this feature! It is nice to see Black Diamond including this feature though – as I mentioned earlier the torch is limited by the battery being sealed in to the torch, so if this is your only torch and you depend on it for walking out that remote crag and you open your bag to find it has been on all day then you'd be a bit stuck! At least with torches with removable batteries this is not an issue as you could just put in your spare set if the same thing happened. Having the lock function greatly reduces this risk.

Head Tilt

The head tilt is pretty minimal; this is one area of functionality where the Iota could be improved. I find that with the torch fully down, I cannot illuminate my feet unless I bow my head forward – while it's not a major issue this is slightly annoying when going down steep hills. However, broadly the range is perfectly acceptable for seeing ahead and down to the ground in front of your feet.


At only 56g, the Black Diamond Iota is one incredibly light headtorch. Its simple, compact, no-frills design ensures straightforward operation (after a bit of getting used to). The built-in lithium ion battery is a decent performer for its size, with micro-USB charging a big plus point for me. It has impressive levels of brightness and is more than capable for illuminating the path ahead on easy terrain. The biggest selling point for me though is how light it is – making it ideally suited to walking, running, camping and climbing. For emergency use, whether stashed in a pack or even in your pocket, its weight is negligible. I will definitely be carrying this headtorch as a backup on all future trips to the hills if I need a brighter one for more technical terrain – I have no excuse not to at 56g! And at a retail price of £40, I consider it good value for money too.

Black Diamond say:

A light that easily fits in the palm of your hand, the Black Diamond Iota is the daily driver for quick-hit morning trail runs, post-work ridge scrambles and urban adventuring. Emitting 150 lumens on the max setting with an average three-hour burntime, the lithium ion rechargeable battery eliminates waste, and an IPX4 rating protects against splashed water from any angle. Powertap Technology allows for fast, easy brightness adjustments, and a lockout feature safe guards your battery life.

  • Lumens: 150
  • Weight With Batteries: 56g
  • Max Distances: High 40m Low 7m
  • Max Burn Time: Low 40hr; Average 22hr; High 2hr
  • IPX Rating : x4
  • LED Type : 1 TriplePower
  • Batteries : Rechargeable lithium ion

For more info see

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27 Dec, 2017
Put that light out!

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