Throw: Head diameter vs. Reflector depth?

But which dimension is a greater influence in beam throw? Diameter of the lens or depth of the reflector (lens to emitter).

What about the die size? Is that relevant to diameter or depth of the head? (For producing high throw)

What about the shape of the reflector? (How it's curved)

What matters is diameter. Depth only plays a small role. Basically it just reduces spill and increase the corona. Diameter is what matters.

Surface brightness of the emitter is also what matters. It's not about a small vs big emitter. In reality it's the small emitter that has the highest surface brightness but it doesn't have to be that way. A large emitter with the highest surface brightness would throw just the same as a small emitter with the same surface brightness.

With a lens (rather than a reflector) it's about the focal length.

the diameter determines the beam width.
bigger diameter => more throw (using the same light source).

The depth determines how much of the light is caught and forced into the beam. good TIR (total internal reflection) optics always catch almost all of the light, so they basically behave like deep reflectors.
deeper reflector (or TIR) => more throw, but no tighter beam.

leds focus better in deep reflectors, (the once that available that is), all shallow large diameter reflectors, that i tried, from 5-20mcp spotlights, ddin't focus leds right,
hotwires like large reflectors, depth also matters, but not as much, otoh the light with the best beam that i have is FM deep reflector ver2, 2" head, with wa1185bulb. even 2,5'' thromaster with the same bulb has beam that is not as uniform and even.

also matters, if reflector is smooth, orange peel or faceted, smooth throws better than others.

You can only increase depth so much before you have to increase the diameter as well. The 2 are related.

One other thing to consider. Reflectors have a hole in the middle for the bulb or LED. A perfect reflector will have a parallel beam with a dark spot in the middle. So reflector makers make less perfect reflectors with a divergent beam to fill in the dark spot. Unfortunately this reduces throw. Aspheric lenses do not have this problem but has its own problem - getting all the light from the LED to the lens.

Wouldn't a basic understanding of parabolas help here?

I think that is the knowledge you need.

obi

To my understanding reflectors and lenses behave very very much the same hence they are both called optics. Consider TIR-reflectors a hybrid between both.
Both have some advantages and disadvantages depending on the lightsource (viewing angle mainly).
Search CPF for ''Formula for calculating throw''.