Just as you shouldn’t judge a book by its cover, you also shouldn’t judge a bike light by it’s lumen output. Even if a bike light has a high lumen output that is FL-1 certified, the beam optics are vital on how well those lumens are translated to the road. Beware of cheap lights that make big claims without testing! A majority of bike lights use simple lens designs that project a cone of light. This means much of the light is wasted on the trees or buildings above you instead of the road and can also blind oncoming traffic. In this review we’ll be looking at the Lupine SL AF 4 which has a dual aspheric lens design that uses optics similar to car headlights to cut-off the light below eye level and focus the beam on the road.

The Lupine SL AF is a headlight designed for those who are looking for impressive beam optics and built to endure daily use for years to come.

The Lupine SL was originally introduced as an electric bike light, but was adapted to use their SmartCore external batteries with the SL AF. There are two models available, the SL AF 4 (which we reviewed here) and the SL AF 7 which has double the battery capacity. As with all of Lupine’s products, the SL have been developed using the ‘buy for life’ principle. This means the build quality is unmatched and results in a IP68 rating (the light can be operated underwater for extended periods of time). There are also additional features such as integrated DRLs and an ambient light sensor to automatically switch between day/night modes that make the SL headlight highly competitive with the latest bike lights on the market. All these features come at a price, namely a $535 retail price (the AF 7 costs $60 more for the larger battery) which is more expensive than many entry-level bikes. 

CategoryBicycle Head Light
Rating 8.5/10
Retail Price $535.00 ($595.00 for AF 7)
Measured Weight (in g) 272 (total): 118 (lamphead) / 140g (battery) / 14 (remote)
Likes+ Premium build quality
+ Crisp beam cut-off prevents glare
+ Various configuration options
Dislikes– Premium price
– Limited side-to-side visibility near light
– Large form factor for lumen output
Where to Buy (US)Lupine


Lupine packages the SL AF4 in a white box with a magnetic clasp holding the lid securely in place. A laser cut foam insert inside the box holds each individual component of the light set securely in place. Lupine includes a number of items In the box:

  • SL AF Lamphead + Quick-release handlebar mount
  • 3.5Ah SmartCore battery pack + short velcro strap
  • Extra-long velcro battery strap
  • Bluetooth remote + Peppi V5 mount
  • Wall charger
  • Torx 5 + 3mm Hex wrench
  • User manual

The box is well made and can be used to store the light when not in use or even travel with it, however, it is pretty bulky if space is limited. Although we typically toss user manuals, Lupine offers an impressive amount of customization so we recommend taking a few minutes to read the manual.


Instead of the typical rubber strap handlebar mount, Lupine has opted for an aluminium quick-release design. The design is similar to the Fenix BC21Rv2 as well as the Planet Bike Blaze SLX lights we’ve reviewed, with the biggest difference being the impressive build quality. Lupine offers three mount options during purchase to accommodate 25.4, 31.8, or 35 mm handlebar diameters. With the quick release design, it’s easy to install and remove the light from your handlebar within seconds without any tools or fuss. The mount also features an offset design (it attaches to the left side of the lamphead) allowing you to have the light centered in front of your stem for optimal visibility. Lupine also offers optional GoPro adapters making the SL easy to attach to popular out-in-front style handlebar mounts.

Lupine SL AF 4 - Mount and Remote
The quick-release mount allows the light to be mounted in front of the stem and the Bluetooth remote has a simple 2-button interface

WIth this light set, you also receive a bluetooth remote that can be used to turn the light on/off and change the output modes.The remote itself is slightly larger than a quarter and is easy to use.However, the included Peppi V5 mount is a basic plastic mount with rubber straps. We found that the mount was easy to use, but didn’t provide a secure fit as the hooks for the rubber straps were shallow. Particularly at this price point, we expected a higher quality mount. Also, after doing a roadside repair, we inadvertently lost the remote over the weekend due to the loose mount falling off the bike. Thankfully, we can report that despite being repeatedly run over and being exposed to the elements over multiple days, the remote still functioned well and only has cosmetic damage.


If the retail price of the Lupine SL didn’t make you realize this isn’t a standard bike light, you will the moment you take it out of the box. The light head is visually striking with the large dual-aspheric lens design that protrudes from the CNC machined aluminium housing. Although it isn’t obvious, behind the lens are 12 Osram LEDs. Lupine describe the SL as the world’s first dual-aspheric lens for bicycle lights and it allows for the crisp beam cut-off by carefully focusing the LED output. Visually, this means as you look into the lens, the LEDs look warped depending on the angle you look at. Around the lens you’ll find an additional 6 Osram LEDs that serve as a daytime running (DRL) light for daytime visibility.

Although the lamphead looks large, particularly with the protruding lens, it is smaller than than the Magicshine MJ-908 and slightly larger than the MJ-906. Above the lens there is also a well designed shield to prevent any reflection of the light from distracting you while riding. The aluminium housing has a powder-coat like finish to it that makes it easy to grip. The Lupine logo is on top of the lamphead and on the left you’ll find an attachment point for the mount. On the rear of the light are the two ambient light sensors that Lupine utilizes to automatically switch between the DRLs and the standard output modes Additionally, there’s an ‘SL’ illuminated cutout that glows blue when the high beam is activated. 

One big weak point with any external battery bike light, are the connection points at the light and between the battery and light head. These connection points can result in shorting that cause the lights to flicker on/off after multiple months of usage. That’s why we were impressed with the SL’s thick cables and robust connectors that feel like they’ll last well beyond the 2 year warranty. The included bluetooth remote is also a nice feature that allows you to power the light on/off as well as set the output mode with two large easy to use buttons. The remote also illuminates to indicate when the high beam is active and flashes green and red as a low battery warning.


One of the major selling points of Lupine products is compatibility and versatility. This means that the included 3.5Ah SmartCore battery included with the SL AF4 we tested here is utilized throughout their product line. This means you can easily replace it and continue to use the light (currently listed for $120.00 for the battery alone) or utilize Lupine’s battery trade-in program. To attach to your frame, the battery has a large rounded rubber pad with simple velcro straps. The rubber pads are grippy and offset the battery from your frame, which prevents it from interfering with externally routed cables and holds the battery securely in place.

Lupine SL AF 4 - Battery
The External SmartCore battery has audible and visual battery status indicator

The SmartCore battery status is easy to check with a large button that illuminates five integrated leds. In conjunction with the LEDs illuminating, there is an auditory beep for each illuminated LED. We were impressed with this auditory battery status feature as it allows you to quickly check the battery status even while riding, without having to take your eyes off the road. Remember when we said you should read the manual?  Lupine has two unique features with the SmartCore battery that are easy to miss: taillight mode and running light mode. Two quick presses activate the taillight mode which will illuminate all 5 LEDs allowing the battery to double as a taillight. Three quick presses will enable the running light mode that flashes each LED sequentially for an interesting visual effect. Pressing the button again will turn either mode off again. 


Lupine has done an impressive job with the optics of the SL which results in a crisp beam cutoff and a trapezoidal beam pattern that focuses the light output on the road. The SL has four unique output modes in the default configuration: DRL mode (1.5W, 17 hr), dim low beam (450 lm, 5 hr), low beam (850 lm, 2.5 hr) and a high beam (1300 lm, 1.5 hr). The runtimes are consistent with other lights on the market and unless you do long rides in the dark, it should last multiple rides. However, we would recommend the $60 more expensive SL AF 7 model which has double the battery capacity and double the runtime for each output mode for peace of mind.

Particularly with the ambient light sensor, the DRLs are a very effective way to maintain daytime visibility without draining your battery. Our only complaint was that the factory transition point between daytime and nighttime mode seemed to be aggressive (perhaps it is tuned for overcast German days instead of sunny California days) and would transition earlier than we expected to daytime mode. However, Lupine allows you to reprogram the transition point to match your desired setting. As with other bike lights with ambient light sensors (e.g. Light & Motion Vya Pro, Bontrager Ion RT/Flare RT), we really enjoyed the ability to simply focus on riding and allow the light to automatically set the mode.

Lupine SL AF 4 - Low Beam
Low Beam Profile

In the night time mode, there are two low beam and one high beam option. The low beam mode has a crisp beam cutoff designed to keep the glare out of oncoming traffic’s eye and focus the light on the road. Using the small button on the bluetooth remote you can toggle between the two power levels of the low beam to either conserve battery life or increase the output. Pressing the high beam button on the remote (or the button on the underside of the headlamp) unleashes the full 1300 lumens and moves the beam cutoff higher to see further down the road. As with a car’s high beam, you’ll want to only use the mode when there is no oncoming traffic or turn night into day. Although 1300 lumens doesn’t sound that impressive these days (some commuter lights like the Magicshine Allty 2000 have nearly double the output), with the focused beam output it feels like a much brighter light in person.

Lupine SL AF 4 - High Beam
High Beam Profile

Lupine also has a number of available configuration options that can be accessed by simply holding down the button on the underside of the lamphead for a specific number of flashes. There are two alternate settings available:

  • (factory config) Dim low beam (450 lm), low beam (850 lm), high beam (1300 lm)
  • (config b) Dim low beam (700 lm), low beam (1300 lm), high beam (1300 lm)
  • (config c) Dim low beam (450 lm), low beam (850 lm), high beam (1000 lm)

We think the standard configuration should be sufficient for most users though as the power output between the modes are large and well defined. Another configuration option is to disable the ambient light sensor and make the DRLs a manual option which may be useful if you want more control.

On the road, the trapezoidal light output is quite unique compared to typical spot or flood beam patterns. The sharp beam cut-off is clearly visible as you ride and keeps the light below eye-level for oncoming cyclists and pedestrians. Due to the lack of glare on low beam mode, it was a welcome treat to get thumb-ups from oncoming cyclists instead of being yelled at on dark bike trails. Our only complaint, and something you can see in the video, is that the beam cutoff is so sharp that taking corners at high speeds can result in dark zones close to your bike as well as further away when leaning the bike. This complaint isn’t specific to the SL headlight though, as other StVZO lights would have similar issues. One way to address this would be to have the light self-center within the mount to keep the beam cutoff aligned with the horizon, although we imagine this would add to the already high-cost of the light.


Overall, we were impressed with the Lupine SL AF build quality and focused light optics. Unlike standard bike headlights that throw a wide beam of light and can blind oncoming traffic, the SL has a crisp beam cutoff that focuses the light on the road. With the StVZO certified optics, the SL also ensures oncoming traffic on the road will give you a thumbs up instead of covering their eyes to avoid the glare. Despite the $500-$600 retail price depending on battery capacity, the build quality and features exceeded our expectations and make us confident that this is a light that can survive years of daily use without issues. It’s certainly not meant for everyone, but for those who are serious about night time riding that want a replaceable external battery and highly tuned beam optics, the Lupine SL AF is an easy recommend.

Disclaimer: The product for this review was provided by Lupine. The views expressed on this website are solely those of the authors and are here to help people make an informed choice before a purchase. The authors or the blog itself does not get any monetary compensation from the product manufacturer or third-party websites/vendor links that are posted here.

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