Originally Posted by
RapidRobert
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.
Amazingly, I fully agree with you on why a simple baffle won't work. Your second statement also demonstrates why cut-offs like the e-code cut-off would be impractical for bicycle lamps. The amount of money required for development of the reflectors and lenses would drive the price per unit impossibly high with little return on the investment, mostly because not many people would buy a $2000 light.