Originally Posted by
mechBgon
I took a shot at a cutoff modification to see how effective it was. The light I used was a Lumapower MRV SK with the OP reflector. I used aluminum foil between the reflector and lens, like this:
The beam looked like this:
I stopped the bike on a dark 2-lane highway and walked out ahead of the bike so I could see how effective the cutoff was. It was not impressive. I went back to the bike, flipped the light over so the cutoff was now an
anti-cutoff, and walked out to observe it again. There was no perceptible difference to me as a pedestrian. So much for that plan. I see people advocating cutoff-equipped lights quite often, but I don't think many have done any first-hand research.
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The baffle you put in front of the reflector in your headlight didn't work because the light it blocked was mostly comming off the reflector and heading toward the hot spot formed by the reflector. I guarantee you made the hot spot dimmer by almost half. The light that's called "spill" comes directly from the source, and "spills" over the edge of the reflector. Also, there's diffraction off the edge of your baffle that only shows up in the far field.
To effectively make a cutoff beam, you'd want to make the reflector itself flat on the top, while keeping its shape for focusing the hot spot beam in the center of the pattern. You could also use a multisegmented lens in front of the reflector, properly shaped sub-reflectors on the main reflector profile, or maybe a lens up real close in front of the source.