Lots of light and some clever features, but beam shape and odd battery-remaining system make it less suitable for road cycling

With a big light output, the Gemini Lights Duo light set blows a clear path down unlit lanes, however fast you want to go.

There is nothing quite like the peace of a well-lit night ride, on road or trail, and Gemini are certainly interested in your enjoyment in the latter. The Canadian company have been around for four years and aim to provide high quality units for a variety of outdoor pursuits.

Their four-cell, 1500-lumen LED front light packs a lot output for its small size. The aluminium head unit is tiny and has two high-power CREE XM-L2 U2 LEDs positioned side by side with a push-button control on the back. The handlebar (and head-mount, as this is included in the box) is a simple O-ring mounting system that has become ubiquitous for many lights. One useful feature of the head unit is that it allows a measure of rotation, so the beam can be directed to left and right as well as up and down.

The output is very impressive. The maximum of 1500 lumens is significant, and even at the 60% setting (about 900 lumens) the intensity and spread of the light is sufficient for unlit country roads with their inevitable potholes and cracks in the road surface. At the lower end setting, 20%, is approx 300 lumens, and about adequate for some urban riding with intermittent street lighting.

In a market where CREE XM-L2 lights are increasingly inexpensive, the Gemini is a pretty steep £170 RRP. For this you do get substantially more that just the head unit. The 5.2Ahr battery pack has some depth (although it does have to drive two LEDs), and is boxed up in a solid plastic housing with a chunky Velcro strap. There is a UK charger unit and head-mounting kit for those who want to fix it to a helmet or use it for running or skiing.

In use it has a good spread and throw, although at lower powers there seems to be some breadth of beam that I'd have preferred out front. The light colour is a bright blue-white. At full power the output is very effective, picking out enough of the riding surface even on a quick descent.

One problem with such a powerful light is that if it is shining on something you don't want it to then it can be distracting. My handlebars have the classic Shimano exposed gear cabling, not the newer design tucked beneath the bar tape and the reflection on the cable outer, even at 60%, was distractingly bright. After a couple of rides I switched the unit so it sat underneath the bar and pointed 'under' the cable more and this made a big difference, although it did tuck the control button away slightly.

The control button is flush to the body of the unit, and its clear plastic displays a colour to show the remaining battery charge (green, orange, red, red-flash). With winter gloves on the button can be a bit fiddly, and a couple of times I struggled to press it without moving the small head-unit itself around. Being small and quite light it was just no match for my imprecise chilly-fingered fumbling.

The control button cycles through three (programmable) brightness settings and the unit is switched off by holding the button down for a few seconds. This is useful as it means that going back to a lower-power setting doesn't mean briefly turning the unit off (as some lights do).

Pressing and holding the button for a few seconds longer sends the unit into a strobe mode. This is useful, but I'm not sure I'd recommend it much for night use at high power as the output level is so high that it is very distracting for both rider and anyone near them. Day or gloomy conditions may be more appropriate, but I'd still worry about the glare it causes. It is worth noting that the strobe level can be turned down to something less aggressive if desired.

A feature I've not seen on any other units of this type is the ability to set your own brightness levels for the three settings. This done by cycling to the setting you want to change and then holding the power button down until it turns to the lowest power mode, from which you can then cycle through the ten brightness levels. Having made your choice you then press and hold the button until it sets it. It's not the most intuitive, and the manual doesn't describe it in much detail, but it does work. It's a great idea and I can imagine some people really appreciating it.

The battery-remaining colour was a big problem – the steps in colour seemed slightly peculiar, and even unhelpful. The green light setting ran for ages, which is fine, but the orange light lasted about 25 minutes on 20% power before jumping to red. Keeping at the same power you then got 45 minutes on red, followed by 90 minutes on the red-flash state.

I would rather have that arrangement reversed. When my bike light displays red or red-flash I'm thinking it's time to recharge, but if there is that much charge left it's too easy to be relaxed, followed by being stranded in the dark. I'd be more likely to expect 30 minutes on the red-flash setting, and to get less than that on orange seems daft. Essentially you get a maximum of 30 minutes between the apparent safety of green and the panic of red – not helpful.

My experience was that mostly using the 60% setting I would get approx five hours of riding (compared with Gemini's claim of 6:40), and I'd be amazed if the 20% setting gave the 25+ hours claimed. Admittedly I was using a rear light off the same battery (MagicShine MJ-818), but I don't think it draws all that much from the battery pack.

This is a good light and probably wasn't quite being used as intended on my rides. I think that for commuting issues such as beam throw and reliable feedback of light run time are more critical. I found the head mount was comfortable, but the weight of battery was too much for running with (it bounced about awkwardly at the back of my head). Hiking and skiing are probably more suited to the weight than pitch-black scampering.

In a world of DealXtreme purchases and easily available copies of well-known brands the Gemini package isn't the cheapest, but the quality is apparent. The casing around the battery in particular looks great, and there is a real attention to detail. The box also comes with an extender cable and head-mount kit for running and cycling (helmet mount), that might be aftermarket with some manufacturers.


A good light, with some beneficial features (the ability to program the brightness-settings being the most impressive), and highest-power setting that will make commuting at any speed on pretty much any road possible. Spread of beam (and some of the accessories) makes it much more suited to the target outdoor market of mountain-bike, trail and skiers.

For general winter cycling it is a solid performer, well constructed and delivering a hefty output – just watch that battery level light, though, as it might not quite be giving you the information you want, when you want it.


Lots of light and some clever features, but beam shape and odd battery-remaining system make it less suitable for road cycling.

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road.cc test report

Make and model: Gemini Lights Duo – 4 cell battery - Front Light

Size tested: www.i-ride.co.uk

Tell us what the light is for, and who it's aimed at. What do the manufacturers say about it? How does that compare to your own feelings about it?

Gemini says:

Double XM-L LEDs. Double the lumen firepower

NEW for 2014, is the DUO LED Light System. Gram-for-gram, it is one of the brightest lights of the year delivering a staggering 1500 lumens and weighing only 63g for the Light Head. Two CREE XM-L2 U2 LED Emitters drive this powerhouse - the most efficient, high power LEDs on the market.

Choose your own ten different levels. 10-100% Brightness.

Pick from 10 different steps between 10-100% brightness and save it. With your own three modes at your disposal, you can personalize your settings to Low-Med-High or High-Med-Low. You may even set the brightness in flash mode so you don't blind oncoming traffic. Getting what you want has never been easier.

By default, the DUO comes with Low (20%), Medium (60%) and High (100%) settings built-in. To reset, just hold the button down for 10 seconds.

Be Bold. Be Visible.

The DUO LED Light offers unprecedented night visibility with the 15-degree standard optics. The DUO emits a far throwing beam that is wide enough to light up the entire width of any trail.

Your Do-It-All Light for All Night Adventures.

We've bundled a bar mount, helmet mount, head belt and extension cable with the DUO LED Light. Explore night fishing, skiing, running, longboarding or mountain biking all in the dark. No longer will darkness stop you from doing the things you love.

Ride safely in town with the flash mode on to ensure you're clearly visible on the road to other motorists.

It seems to be aimed more at outdoor pursuits than cycling as such, and in terms of cycling the Gemini website seems most interested in urban and mountain biking. I'm a roadie-commuter, but night is dark for everyone at the end of the day!

I think that the spread of the beam would probably suit trail riding more than road, but at the higher power settings the output is significant and picks up the road surface well in enough time to react.

I found the weight of the battery made running very uncomfortable (it bounced about on the back of my head in a slightly comedic manner), but for cycling in the dark it certainly delivers.

The ability to meddle with the brightness settings is something I've not come across before, and works well once you get used to how the system works.

Tell us some more about the technical aspects of the light?

Control and battery level feedback are all managed through the single button on the head unit, which given what it is asked to do is ambitious. It does seem to work, with the most complex of the tasks being how the custom light settings are managed. After a few goes it made sense enough for me to manipulate them easily.

I wasn't impressed with the stepping in the battery-remaining colours, and thought that there was confusing feedback.

Rate the light for quality of construction:

It feels well made – the casing around the 4-cell battery is solid and the wide single Velcro strap does an excellent job. The head unit is small, with a simple (and widely-used) single rubber o-ring fitting. Despite its size it feels like it is a quality construction.

Rate the light for design and ease of use. How simple was the light to use?

Simple to use, but the stand-out feature of programming could do with some more explanation in the manual. It's a great idea but required a little too much vague button pressing before I fathomed out how it was supposed work.

If I could have tweaked the battery-level colour settings then I'd have been very happy, but you are left with a pretty narrow time span from looking OK to mild panic.

Rate the light for the design and usability of the clamping system/s

The head unit is fixed with a (now pretty ubiquitous) single O-ring fitting (a range of ring diameters are supplied in the box for different bar sizes).

Rate the light for waterproofing. How did it stand up to the elements?

The head unit hasn't failed under some impressive rain showers, and the plastic casing round the battery looks pretty solid.

Rate the light for battery life. How long did it last? How long did it take to recharge?

Charging takes a few hours from a (supplied) mains charger, and takes about 3-4 hours from probably 25% of battery remaining. The battery lasted me about 5h on 60% charge while also supporting a rear light.

Rate the light for performance:

1500 lumens really is a hefty output, and more than enough for unlit country roads in the middle of winter. The light spread and throw are excellent, particularly at the higher output settings. This and the simple control system are let down by slightly inconsistent battery level information.

Rate the light for durability:

The unit performed very well in all the usual British weather conditions, including some vigorous winter storms. There are no signs of it packing up due to water ingress (unlike the rider on those occasions!).

Rate the light for weight, if applicable:

The aluminium head unit is small and weights very little in comparison with the plastic-shell 4-cell battery pack. Gemini claim 63g for the head unit, but don't provide any claims for weight of the four-cell battery pack.

Rate the light for comfort, if applicable:

The head unit is very small and doesn't cause much clutter on the handlebars.

Rate the light for value:

£170 is a lot of money in a competitive market for high-performance lights. Gemini's comprehensive package of accessories with the Duo 4-cell closes that gap, and makes it comparable with other brands at this output level.

Tell us how the light performed overall when used for its designed purpose

The light output is excellent – I didn't ride it off-road but I can imagine it would do an excellent job. The nearest I got was some torn-up country lanes and it gave me ample light to read the road by.

Tell us what you particularly liked about the light

Once you start using the 100% setting you just don't want to turn it back down! The left-right tilt on the head unit is very helpful. I'm impressed by the ability to custom-set the brightness of the beam.

Tell us what you particularly disliked about the light

The mystery of the battery-level colours – flashing-red setting should be a serious warning, not offer twice as much run time as the previous two colours. It was so bright on high-power modes that other parts of the handlebar area, like cables, could be distracting.

Did you enjoy using the light? Yes.

Would you consider buying the light? No. It's probably too much for what I need.

Would you recommend the light to a friend? Probably not – most of my cycling friends aren't off-roaders, and I think this unit is best suited to that sort of riding. For those that are, though, I'd suggest it happily.

Anything further to say about the light in conclusion?

A light that I suspect is excellent for off-roading or outdoor pursuits, but for a road commute it didn't feel like it had quite the right mix of light throw at lower brightnesses, battery life feedback and control.

Overall rating: 7/10

About the tester

Age: 37  Height: 182cm  Weight: 69kg

I usually ride: Specialized Allez Sport 2008  My best bike is: Moda Tempo 2010

I've been riding for: 5-10 years  I ride: Every day  I would class myself as: Experienced

I regularly do the following types of riding: time trialling, commuting, touring, sportives, general fitness riding, Triathlon



Bike Swanky [66 posts] 4 years ago

Having hooned down Combe Lane at night in the wet, I'd always recommend a bar and a helmet light if possible. Bar only is good if you are on a fairly smooth, non undulating road surface at a regular pace.

However, if it undulates, the height of the light on the bat will lead to blind spots on the road in front of you, and you need a long throw of light at speed.

Having a light at head height overcomes this and lets you throw the light where you need it and not just where you're pointing.

The only downside to this set up though is that you'll need to put the battery somewhere if it's not integrated.

It could sit in a pocket or in a small hydration bag without throwing your centre of gravity off course.

Anyway, that's my own experiences shared. Feel free to comment  1