Large head or small head: What's the difference?

smooth2o

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It seems that even small lights have a great throw and a nice small beam pattern. So, what's the difference between the large or small head? For example, I am looking at the Nitecore P12 vs the P25 and see that the difference in throw is 232 vs 283, not that much of a difference for having such a large head on the P25.

I would assume that there is also a difference in cooling, but according to the reviews, the P12 can be on for 20 minutes before step-down.
 

Chicken Drumstick

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Reflector size does directly affect throw. Put and XM-L2 in a small tube light and you'll get a large hotspot that isn't tightly focused. Put the same emitter in a larger reflector and you get a smaller more tightly focused hotspot and a more defined difference between spill and hot spot.
 

Timothybil

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Reflector size does directly affect throw. Put and XM-L2 in a small tube light and you'll get a large hotspot that isn't tightly focused. Put the same emitter in a larger reflector and you get a smaller more tightly focused hotspot and a more defined difference between spill and hot spot.
Reflector size doesn't really affect the 'length' of throw. What it does affect is how much of the total output goes into the hotspot and how large and how bright the spill area is. There is some affect on length, because a large reflector will collimate the beam more, in effect giving one more point sources instead of a single one for the inverse square law to affect.
 

mpett1

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I have a Fenix E21 and E20 and both are great throwers and have a tiny small head so I dont get it. My Thrunite TN12 no where near as tight and am thinking of selling it.
 

smooth2o

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So, if a larger reflector collimates the beam more, then the hot spot of the light with the larger head should be smaller at a given distance. Additionally, more of the light output (lumens) will find their way to the hot spot of the light with the larger head. So the hot spot of the light with the larger head is brighter at a given distance. In that you usually shine the hot spot on an object, the light will have a longer throw (more light to light up the object).

So, for two lights of equal output (lumens),
The smaller head will have a larger hotspot, less lumens in the hotspot and a larger spill area. Less throw.
The larger head will have a smaller hotspot, more lumens in the hotspot and a smaller spill area. More throw.

So, for example, if I was looking for buoys, which light do you think would be better? Buoys are hard to find. On the one hand, you can find one a long distance away with a tighter beam but that's harder to do. On the other hand, you can find them better with a larger beam, but they are closer.
 

scs

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I have a Fenix E21 and E20 and both are great throwers and have a tiny small head so I dont get it. My Thrunite TN12 no where near as tight and am thinking of selling it.

The depth of the reflector also affects it. Exactly how the diameter and depth of a reflector (also its shape) interact to determine hotspot beam angle, hotspot size, hotspot intensity, I hope someone can clarify it.
 

scs

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My wild guess is a deeper reflector directs more light rays into the hotspot and a wider reflector minimizes the hotspot beam angle.
In other words, a deeper reflector makes the hotspot brighter and a wider reflector "contains" the hotspot more, making it diffuse less with distance.
I see a potential paradox. Keeping the depth of the reflector the same, I think increasing its diameter would take away light rays from the hotspot.
So perhaps it's an optimization problem: for a given reflector depth or reflector diameter, there is a corresponding reflector diameter and depth respectively to yield maximum throw.
 

thedoc007

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It seems that even small lights have a great throw and a nice small beam pattern. So, what's the difference between the large or small head? For example, I am looking at the Nitecore P12 vs the P25 and see that the difference in throw is 232 vs 283, not that much of a difference for having such a large head on the P25.

Remember that throw (range, distance, whatever you want to call it) has an inverse square relationship. I.e., if you move twice as far away, you get only 1/4th of the lux on target. 232 vs. 283 is definitely a very noticeable increase in intensity, and that is due almost entirely to the larger head on the P25.

I would assume that there is also a difference in cooling, but according to the reviews, the P12 can be on for 20 minutes before step-down.

That is not correct. The P12 steps down after only three minutes. The P25 runs a full twenty minutes on turbo (over six times longer). I have two Nitecore P25s (one Vinh modified) and they are definitely MUCH better at absorbing and dissipating the heat on higher modes, as you would expect.

My wild guess is a deeper reflector directs more light rays into the hotspot and a wider reflector minimizes the hotspot beam angle.
In other words, a deeper reflector makes the hotspot brighter and a wider reflector "contains" the hotspot more, making it diffuse less with distance.

A deeper reflector means tighter spill beam...the Armytek Predator, for example, has a relatively narrow, but deep head. It has a much smaller spill angle than almost every other light I own. The hotspot is dominated by reflector width...you can get pretty good throw out of even a very shallow reflector, if it is wide. See the TM06vn, for an example. To get the best throw, you need both. The more light that you can get focused, the better it will be for long range use.

We all have to remember that reflector size/shape is only one aspect of throw, though. Raw output matters (scales 1:1, so 50% more output means 50% more beam intensity, all else equal). The size and surface brightness of your chosen LED has a tremendous impact as well. A light that throws quite well with XP-G2 might have hardly any throw at all with MT-G2 (assuming it would fit).
 
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Chicken Drumstick

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I have a Fenix E21 and E20 and both are great throwers and have a tiny small head so I dont get it. My Thrunite TN12 no where near as tight and am thinking of selling it.
I think they are XP-E, which is a much smaller LED. Hence the relationship between LED size relative to reflector size. The XM-L2 in the TN12 is a large LED in a small reflector.
 
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