That means no matter how large the emitting area is, the LED (with a given luminance and reflector) will throw the same distance. Then the only thing that changes is the hotspot size?
But increasing the reflector/lens area “seen when looking into it” gives better candela —> more throw.
Right?
And pushing more power through the LED increases the luminance?
Here is the formula:
Luminus_intensity [cd] = luminance [cd/mm^2] * area_of_reflector_or_optic [mm^2] * losses [%]
Losses being the reflectivity of the reflector (or the transmission rate of the optic) and the transmission rate of the lens.
Generelly small LEDs which tolerate very high power densities reach the absolute highest luminance values. The Luminus CFT-90 is an outlier.
wait, so luminus intensity doesn’t depend on reflector shape?, so what if i have a very deep reflector( like 2cm diameter OTF) and 20cm OTF but narrow, both have same area, they will throw the same, right ?
No, it doesn’t. That’s a very common misconception.
If you have two reflectors with the same outer diameter but one is deeper, the deeper one will have a slightly smaller led opening. This increases the total reflective area slightly. The larger the reflector, the less important this becomes.
At constant diameter? Deeper reflector = larger hotspot……
Same intensity * more lm collected by the reflector = larger spot
Saying same thing in other terms…
All parabolas are the same except for the scale. All parabolic reflectors are (geometrically) the same except for the scale and 2 cut points.
Scale is usually expressed in terms of focal length (FL).
For a given emitter beam angle depends on FL and on nothing else. Larger FL = narrower beam.
For constant diameter, larger FL = smaller depth. So less deep = smaller spot.
You need to differentiate between hotspot and corona (“coma”). Deep reflectors (at the same outside diameter and same size LED) make the actual hotspot with maximum intensity smaller and the corona surrounding it bigger. The corona also has a high intensity, much higher than the spill, but noticeably lower than the hotspot itself. This fills in the dark gap between the hotspot and the spill when shining the light into the distance. This can create a more practical beam.
Armytek uses very deep reflectors. You can compare beamshots of them with those of lights from other manufacturers.
Same goes for, for instance, the Thrunite TN31.
Deep reflector, small hotspot, large corona.
Take out the XM-L2 and replace with a (decomed) XP G2 and you get an even smaller hotspot and an even bigger corona
The large corona makes these intense hotspot throwers more usable because you can still illuminate something next to the hotspot.
Example of a thrower with shallower reflector and thus larger hotspot (but almost no corona): Olight M2X Javelot and Amutorch JM07.
No one can accuse me of having in dept knowledge of the physics behind it all; i draw my knowledge from field experience.
And I like to read a lot about things I like
I also like that shallow reflectors have a wider spill beam, making for slightly better illumination of immediate surroundings. I value that quite a bit as well.
Difference between 100mm and 120mm depth with 120mm width (iirc)
With a shallower reflector, the focal distances are always larger, thus more throw.
Yeah you have a little more / wider spill, but i don’t think that makes too much of a difference for the throw.
Basically that a less deep reflector is better for throw, when the diameter is fixed.
Focal distances are longer with less deep reflector, because it’s a larger parabola than a deep one.
Added depth doesn’t add much light hitting the reflector.
Your drawing is a bit misleading i.m.h.o. because it ignores the radiation pattern of the LED.
All domeless LEDs have generally the same radation pattern. They are basically lambertion emitters.
The depth of a reflector for a given diameter has no noticeable effect on throw. It just changes the proportions of the different parts of the beam. It’s simple math.
You have made these statements multiple times, but your diagrams don’t prove them. They don’t show anything pertaining to luminous intensity (throw) except for the diameter of the reflector.
The focal length of reflectors does not effect throw.
