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From: Roger Merriman <roger@sarlet.com>
Newsgroups: rec.bicycles.tech
Subject: Re: For those who believe in electricity
Date: 12 Apr 2025 08:25:09 GMT
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Frank Krygowski <frkrygow@sbcglobal.net> wrote:
> On 4/11/2025 3:24 PM, Roger Merriman wrote:
>> Frank Krygowski <frkrygow@sbcglobal.net> wrote:
>>> [about headlight beam optics, generating "specially shaped beams":]
>>> I don't think that's true at all. Take a look at some of the beam shots
>>> at this site: https://bikelightdatabase.com/beamshots
>>> 
>>> Or go to
>>> https://road.cc/content/feature/roadcc-front-bike-lights-beam-test-310999
>>> and look at the beam shapes of the Ravemen and the Knog.
>> 
>> Both of which have shaped beams, Raveman and Knog both claim road specific
>> beams and reviews tend in Road.cc and others mention this, Raveman make lot
>> out of their High and low beams, though they are far from the first to do
>> that sort of thing!
>> 
>> I get why they do this, but a camera isn’t an eye and it’s rather false if
>> not misleading to use beam shots.
> 
> I think you and I have different definitions of beam shapes, and 
> different standards. (Andrew will be thinking "Of course!")
> 
> But the beams shown for the Raveman and Knog are rotationally symmetric. 
> That can be called "specially shaped" only in comparison to totally 
> random shapes, or to a light source with no focus at all.
> 

Don’t trust road.cc beam engine it’s like others trying to simplify and the
eye perception is very different to a camera.

Try lights one knows and have used and compare if one wishes to test it.
Note also they are not testing at different power levels which in number of
lights will change the beam shape, ie on high it will have a higher beam
shape vs low, the Strada I have very much has this, and they have clearly
only tested on high.

Raveman in particular make a thing about having a T shaped beam which is
anti glare they claim.

And this is backed up by reviews of their lights including Road.cc

Will it be as cut off and low as a StVZO light? Or even the Exposure Strada
which I have old version? No i suspect not but does appear to have some
attempts to angle and shape the beam.

> Here's a good article on beam design that highlights the shortcoming of 
> a round beam for road use. 
> https://www.renehersecycles.com/myth-14-more-lumens-make-a-better-light/
> Essentially, the illumination of the road surface can't be uniform. It's 
> closest to uniform if you're wasting half the light above the road 
> surface. Otherwise it generates hot spots that are detrimental to your 
> night vision. A properly designed beam will do a much better job of 
> giving uniform illumination and will better show road contours, 
> obstacles, potholes, rocks etc. The information is much the same as the 
> Peter White article below, but with graphics that may make the ideas 
> more clear.
> 
>>> In the past few years, there's been more attention to optics, but I
>>> think there are still plenty of small manufacturers who use rotationally
>>> symmetrical optics. Peter White has an explanation of why those are far
>>> from optimum, at https://www.peterwhitecycles.com/plight.php
> 
> 
> 

Roger Merriman