A worthwhile investment for the year-round commuter and occasional night time trainer
Exposure Sirius Mk4 front light
9 10

The Exposure Sirius Mk4 has gained another 100 lumen over its predecessor but there is more to it than just pure power. It's a clever little light that is good enough to be used on its own, as a backup or getting the commuter noticed year-round, all in a small, lightweight package.

UK brand Exposure has a huge range of lights, and the Sirius sits in amongst the smaller mini torch shaped ones like the legendary Joystick (we tested the Mk 10 last month). They all follow the same design, a one-piece, CNC machined alloy body with an internal battery. It makes for a compact unit and the Sirius weighs just 79g including its plastic bracket and rubber o-ring fixing.

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Up front you get a single LED, which on its maximum setting pumps out 500 lumen for two hours from the single 2,600mAh lithium ion battery or 36 hours on its lowest. With seven different settings on offer, thanks to Exposure's Optimum Mode Selector you can tweak the Sirius to emit the brightness/burn time ratio you require.

It's simple to set up: you just press and hold the on/off button until the number of flashes corresponds with the setting number. They're printed on the bottom of the light so you don't need to memorise them. With all of the settings you also get the pulse function if you hold the on button for just a little longer than normal.

You can keep an eye on the juice level by the colour of the on/off button – it changes from green to amber to red as the charge drops. A charge time of four hours from completely flat means that most people could charge it up at work to avoid getting caught out on your next ride. The light comes with a USB charger cable.

It's in the urban environment that it works best. The bright white light stands out in the orange hue of streetlighting in any mode, but as a commuter I would tend to have it on pulse more often than not as it is really eye-catching without being antisocial, especially when filtering through busy streets. In pulse mode the LED stays on the whole time on a low mode while emitting a stronger 'flash' at a constant pace. It's bright enough to work in daylight too.

Exposure Sirius - beam shot.jpg

Exposure Sirius - beam shot.jpg

Fitting is easy: a simple curved bracket for the light to be pushed into holds things firm, with a ladder style o-ring keeping it in position on the bar. It makes for simple attaching and removing should you need to leave your bike during the day in public. The light body can sometimes slide forward because of vibration but it's not really a problem.

On unlit roads the beam is usable if not really ideal, as it is very focused in the centre without much light thrown to the sides. You can still ride at a decent pace though – on dark lanes I was quite comfortable up to around 25mph with regards to seeing potholes and the like, though you can knock 5mph off that if the surface is wet and less reflective.

The Sirius comes with the same Smart Port Technology as the rest of the range. You can plug things into the rear charge port, such as Exposure's Red-Eye rear light or piggyback batteries, which can make the light quite versatile.

The charge port does always have a small amount of power going to it even if it's not being used, so you need to make sure the rubber cover is closed if you are riding in the rain. Earlier lights didn't have this cover and they could short out, returning to normal once dried out. I've never had this issue with my own Sirius Mk1 or this latest version, mind, and it's seen plenty of heavy rain.

The Sirius is built in the UK and comes with an impressive two-year warranty, but should you have any reliability issues Exposure is renowned for its customer service.

In conclusion, the Sirius Mk4 is an excellent little light for a range of applications. It excels in towns and cities, with that bright pulse setting making you seen when filtering through traffic, and the sheer number of modes means you can set it up exactly how you want it.

> Find more front lights and our beam comparison engine here

At just 79g and 100mm long it's easy to keep in a rear pocket or rucksack as a backup to your main light, and thanks to its brightness it'll get you out of any dark trouble you find yourself in.

Compared with some lights on the market the £99.95 price tag might seem steep, but you really are paying for what you get here: the solid body and technology all backed up by top notch customer services should things ever go wrong.

My own Mk1 is a fair few years old now and has never failed me, and still puts out the same burn times as it did when new.


A worthwhile investment for the year-round commuter and occasional night time trainer

road.cc test report

Make and model: Exposure Sirius Mk4 front light

Size tested: n/a

Tell us what the product 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?

Exposure says: "The Sirius is built to excel in urban environments. With a 500 lumen output, suitable for off-road riding and side illumination it rules the road. The Sirius will keep you safe and seen for miles with; constant and pulsing modes, long battery life, USB charging and OMS for adapting burntimes. Every Sirius is hand built and individually tested in the UK."

It certainly is a clever little light that is capable of many tasks.

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

- Smart Port Technology +

- Cable Free Design

- Intelligent Thermal Management

- Optimum Mode Selector

- Fuel Gauge

- Hand Made in the UK

In the box: Sirius MK4, QR handlbar bracket, USB charge cable, Quick start guide

Rate the product for quality of construction:

Exposure lights are really well put together – solid engineering.

Rate the product for performance:

Excellent for urban applications but can cope with much more.

Rate the product for durability:

No flimsy complex brackets or weak buttons in sight. It's been dropped and soaked many times with no issues.

Rate the product for weight (if applicable)

Barely noticeable on the bike or in a rear pocket for emergencies.

Rate the product for value:

You get what you pay for. I don't think you are getting a bad deal considering the quality of the light.

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

Brilliant as a commuter light or backup to your main.

Tell us what you particularly liked about the product

The range of modes.

Tell us what you particularly disliked about the product

The bracket can sometimes move through vibration.

Did you enjoy using the product? Yes

Would you consider buying the product? Yes

Would you recommend the product to a friend? Yes

Use this box to explain your score

The Sirius Mk4 is a cracking little light that does everything it is designed to do well. As a commuter light, the range of options and that pulse setting are perfect, offering decent burn times and quick charging. The underlying fact is that you are paying for the quality and the design; you always know it's going to turn on and get you home regardless of weather conditions.

Overall rating: 9/10

About the tester

Age: 37  Height: 180cm  Weight: 76kg

I usually ride: Kinesis T2  My best bike is: Mason Definition

I've been riding for: 10-20 years  I ride: Every day  I would class myself as: Expert

I regularly do the following types of riding: time trialling, commuting, club rides, sportives, fixed/singlespeed

Stu knocked out his first road.cc review back in 2009 and since then he's chucked the best part of seventy test bikes around the West Country, a couple of them quite literally! With three alloy and two steel bikes in his fleet he's definitely a metal man (that'll be the engineering background) but is slowly warming to that modern carbon fibre stuff along with fat tyres & disc brakes.
It's not all nostalgia though, after spending the last few years in product design Stu keeps banging on about how 3D printing is going to be the next big thing and he's a sucker for a beautiful paint job too.


SkinnyGoat [5 posts] 2 years ago

It is a great light, best I've ever owned.  Sure it is a little bit on the pricey side, but just feel the quality.  It feels so solid and well built.  I've worked my way through various crappy cheapo lights and also a couple of Lezyne powerdrives.  All eventually failed, but this light is the business.  I use it primarily for commuting.  But I've also used it out in the countryside at night and it lit the road up sufficiently to keep me confident of being seen and being able to see.  I bought it as a set with the Trace R rear light.   I wish I'd bitten the bullet earlier and invested the money in a quality light rather than waste it on cheaper lights.

BikeJon [210 posts] 2 years ago

I still have and use my Joystick MAXX 2, which is about 10 years old now. Whilst the lumens output now seems to be from the dark ages (geddit!) it's still seems bright enough to me and is a useful commuter light. Remarkably the battery life seems undeminished. Exposure lights really have excellent build quality in my experience.

The only reason I want this Sirius one instead is due to the SPT+ (Smart Port) so I can run my Red Eye from it. My Joystick is too old to have this tech. I run the Red Eye with the excellent Exposure Revo dynamo light in the depths of the winter but like to switch to a lighter setup (i.e. ditch the dynamo wheel) after the clock change in the spring.

I do use the Exposure Trace rear too but I find these only last a couple of years of frequent use before the circuitary plays up. They switch modes or even turn off after this time. This is a shame as they are very bright.I'm not sure if the Trace-R is any more robust?