I wonder if B&M have good illustrations of their beam patterns? They are a lot like automotive lights... they try to put most of the light onto the road 50 or 100 feet (or more?) ahead of you where it can do some good. Very little is allowed to be above the road and shining into people's eyes. With modern car lights, they have gotten good at creating a sharp cut-off at the horizon, to the point that if the car hits a bump or goes over a small hill, the high intensity part of the beam will be shining into the eyes of oncoming traffic and really blinding them.

My own headlights don't have the benefit of this sort of technology, and are just round beams. Not ideal, but available. There are datasheets for the optics that I use, such as the Ledil "Heidi" optic. It is used with a small LED, and comes in a few versions with different width beams. The ones that I chose have a narrow-ish beam, where the intensity of the beam has fallen off to half of the peak intensity by the time you get to 4 degrees off from the center. This is how the datasheet shows it...


There's not a ton of info on bike light beam patterns. I know that Peter White has put a fair bit of effort into taking pictures of the beams of the lights that he sells.

Steve in Peoria