Sigma Stereo taillamp (battery)

I wrote on the main page:

Regarding battery powered taillamps, that usually don't interest me, I would be interested to have a look at the Sigma Stereo that can be charged via USB connector and that may have a good lichtdistribution.

It is clear that it is largely predictable from product photos and photos with the lamp on, whether a taillamp is good or bad. Often pictures of the lamp with light on are not even required...


StVZO approval no: K969 (non-flashing version only!)
Mass: 72 g (with batteries and O-ring).
Size: 74.7 mm width, 41.0 mm height, 21.6 mm thickness (excl. part that sticks out for the mount).
Light source: 2 red LEDs.
Mounting method: On the seatpost. You can adjust the angle.
Batteries: 2 x 800mAh low self-discharge NiMH batteries are included.
Construction: Plastic.

Price: ca. € 30,-

Power: 24mA at 2x1.30V means 0.062W


I like how it looks, a lot less clunky than the Lightring taillamps...

Beam shots

See the camera settings page for more on the setup and settings to make pictures of the beams of taillamps.

Out of a corner (showing how much light is cast upwards, forwards and to the sides) [ F3.9 & F1.8 ]:

Wallshot (showing the beam pattern):

Visibility from various angles (0°, 45°, 90°, 135°) [ 0.5m, zoom x3, F3.5, ISO80, 1/250s & 1/60s ]:

Comparing taillamps


The optics are pretty good, no blinding of trailing cyclists, the light is distributed very well over a larger area which is the ring around the LEDs but the LEDs light up a bit in the middle too (and not as a point source!). The light at close range can be annoying to some (I asked someone else to judge it too), so better distribution over a bigger surface is still what we need, not a higher intensity. There is a section of light in the beam that is nearly collimated so it gives good long distance visibility despite low power consumption similar to the Lumiring.

The rubber cap on the micro-USB port is a bit hard to get off but even more difficult to get back in, but I suppose that means it will be waterproof there :)

The mounting method is by rubber band which Sigma thinks is cool for bike computers and lamps, but which in reality sucks harder than a black hole. The on-off switch is not as good as on the Lightring, in particular because of key-bounce (result: light going off immediately after pressing on, or not going off when it's on) and you need to press it too hard.

The included batteries are of the low self discharge type, charged and ready to use when you buy the lamp.

From a recent comparison with the Philips taillamps (see the comparison page on taillamps):

Long distance comparison of the Sigma Stereo, Philips Lumiring & Philips Lightring: I cycled towards them several times from ca. 300m, lights positioned at about 1m and another at near road level. This height difference didn't matter much in visibility... The Lumiring is best for close distance (not annoying, gives the feel of a solid object) and for long distance works just as well as the others, with very low power consumption, which shows the superiority of the optics and concept. The Sigma stereo also has a almost collimated section of light in the beam like the Lumiring which gives it long distance visibility with little power used. The lightring is perhaps a little better on winding roads (out of the direction of the 'almost collimated' part of the beams which go straight to the rear in a narrow cone, of the Lumiring and the Stereo) but the Lumiring is good enough. Do you really need to be seen further than say 200-300m if the road is meandering? It seems to me not, but if you have experience in such situations, and have some suggestions, let me know.


The Stereo has a good total concept (NiMH batteries with micro-USB port) coupled with smaller mass than the battery version of the Lightring and it looks nicer than the Lightring. Visibility is good, it doesn't annoy trailing traffic (some people won't like it nearby, too bright), the mount with the rubber rings sucks.

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