Cyclothesist wrote: ↑4 Dec 2023, 4:35pmIn theory it should be possible to deflect the light beam to a lower and wider profile using a stick-on fresnel lens.
All the stick on fresnel lenses I've seen for bike lights just spread the light left & right, but do nothing to the vertical spread, so as far as anti-dazzle is concerned, or light of the road directly ahead, it's the same as turning down to half power.
Basically, one reflector/lens and one LED means one beam pattern, with the only control being power.
If you are willing to rig up an arrangement to manually flip a fresnel lens across the front of the light, a sort of dip would be possible. You'd still have a round torch style beam, but it would be aimed closer.
If you want to try it, I'd suggest a section cut from the edge of one of those
wide angle view stick-ons you occasionally see in the back window of a VW Camper or similar, arranged to give as near horizontal ribbing as can be managed.
It's far simpler to just twist a bar-mounted light down though.
To get car-style main beam/dip beam lighting, you are going to need to switch between separate LEDs.
Such lights do exists for bikes, most commonly as e-bike lights powered off the bike battery, but there's also a very expensive Supernova separate battery light (M99 mini), and B+M (IQ-XL) and SON (Edelux USB-FL) have announced dynamo versions for next year.