Reflector depth compensate for small diameter?

[brightnorm]

To what extent is this possible? For example, would a 1/2" deeper L4 reflector have a significantly tighter focus?

Brightnorm

 

[Size15's]

I think the light source would have to get smaller if the depth was increased. Lets face it, the 5W Luxeon is large light source compared to a bulb filament.

Al

 

[McGizmo]

The deeper a parabolic reflector is, the more off axis light is redirected into the center beam and the tighter the spill beam angle becomes. To tighten the reflected beam, a larger scale parabolic surface is required.

- Don

 

[Doug S]

[ QUOTE ]
McGizmo said:
The deeper a parabolic reflector is, the more off axis light is redirected into the center beam and the tighter the spill beam angle becomes. To tighten the reflected beam, a larger scale parabolic surface is required.

- Don

[/ QUOTE ]

What Don said is exactly right. Usually I avoid "me too" posts when the original poster is a known, respected, and creditable source. What I want to call attention to is the remarkable efficiency of Don's post. There is a lot of information conveyed without a single wasted word. The original question was completely answered and the principles applicable to the general case are also conveyed. This is a high standard of posting efficiency that is only rarely met. I wish that my own writing was as succinct.

 

[brightnorm]

[ QUOTE ]
McGizmo said:
The deeper a parabolic reflector is, the more off axis light is redirected into the center beam and the tighter the spill beam angle becomes. To tighten the reflected beam, a larger scale parabolic surface is required.

- Don

[/ QUOTE ]

Don,

Please bear with my denseness but I need to clarify this for my own understanding which is that a deeper reflector redirects more off axis light to the center and spill beam angle tightens. Doesn't that equate to a visibly tightened beam? Unless that in and of it self doesn't produce a visibly tightened beam unless a larger diameter reflector is used?

My confusion is genuine, even though it's crystal clear to you and Doug who is also an engineer. The confusion is with the first sentence which seems to be a yes answer to my question. The second sentence confuses me because it seems to contradict my obviouly incorrect interpretation of the first sentence.

Please bear with me on this Don. BTW, I had always thought the same as Al about source size. Is that accurate?

Thanks,
Brightnorm

 

[asdalton]

[ QUOTE ]
brightnorm said:
Please bear with my denseness but I need to clarify this for my own understanding which is that a deeper reflector redirects more off axis light to the center and spill beam angle tightens. Doesn't that equate to a visibly tightened beam?

[/ QUOTE ]

A deeper reflector will intercept more light and project it forward, but that's not the same thing as having a tight beam. If you want the rays of the beam to be approximately parallel (giving a narrow hotspot), then the light source needs to be much smaller than the radius of curvature of the reflector. You can achieve both efficient light capture and a tight beam by using a deep and gently curved reflector--which by its nature must also be large.

 

[Doug S]

Norm, let me take a shot at this. I think there is a semantics problem with "beam". The deeper reflector makes the center hot spot brighter but not smaller. It does this by redirecting some of the light that would have been "side spill" with the shallower reflector. So yes, you are right that the beam consisting of the total beam including side spill is tighter with the deeper reflector.

 

[brightnorm]

Thanks guys, that is helpful.

BN