Reflector size question

[me3]

A bit of a debate on another forum.

I can't figure out why (in general) larger reflectors are better.

Essentially you can get a good beam from a huge cheap light. You can get a good beam from an expensive medium sized light. I have never seen a good beam from a small light.

To my thinking a parabola is independent of size. So, why do bigger reflectors perform better?

Thanx
Paul

 

[Th232]

If I'm reading your question correctly, then I'd say that the reason is because the light emitter isn't a point source, hence the size of the reflector does matter. The larger the reflector, the more the emitter can be approximated as a point source, and thus the better focussed it'll be compared to a smaller reflector.

That said, I've found excellent beams from McGizmo's reflectors, regardless of size (or the difference in quality is so small that I can't see it).

Oh, and :welcome:

 

[-Virgil-]

The primary reason is simple and intuitive: the larger the reflector, the more light can be collected from any given light source. In practice it's more complex than this; for any given reflector mouth size, focal length has a significant bearing on the amount of usable light flux collected; also, focus issues as TH232 describes come into play as a secondary factor.

 

[me3]

Somethign there doesn't make sense.

Take 3 lightforce lights - same design, same construction.
140mm, 170mm, 240mm

whilst the 140 has a 75 w bulb, the others both have the larger 100w bulb.

The output of the 240 is quoted at nearly twice that of the 170.

if the reflector is 99.99% (at a guess) and covers the same ARC of the bulb - they should be the same.

Something is missing here (apart from my brains)

Thanx
Paul

 

[-Virgil-]

Lightfarce tells a lot of lies, what's one more?