6" Long Reflector on E21

[EasyB]

You are correct it’s not just the outer diameter that matters, it’s the frontal area. To find this you subtract the area of the small inner circle from the area of the large circle. But because of the way area grows with diameter the inner circle area is always relatively small. So making the reflector shallow, within reason, doesn’t have a huge effect on the frontal area.

@Joshk

And here’s the base of my argument… A a larger reflector that has the same “degrees of light captured”. The larger one captures the same total light, but makes a larger, less intense hotspot with it.

This is not correct. Most flashlights use reflectors with similar collection angles. So would you expect, for example, that the BLF GT reflector would make a larger less intense spot than a C8 reflector, with the same LED? This is obviously not the case.

Please put your current understanding of this subject aside for a moment and read this:

Flashlight Optics - Dome, Dedoming and Throw

I wanted to write a longish text about flashlight optics for quite a while now, starting with all the optics and photometry basics, up to the details of what throw depends on and why, including how dedoming increases throw, all with a coherent line of argumentation and some experiments to try. I even started writing that document, but it seems I just don't find the time to finish it in reasonable time. I now decided to take a shortcut and just do a very short version of it, especially focusin…