So the bigger and deeper the reflector the longer the throw? Mf04/MF05?
The smaller the LED the longer the throw? Osram?
What would happen if you combined the two: large deep reflector and Osram LED, and more important why has this never been done. At least not that I have ever seen.
[ADDED] I AM NOT ASKING WHICH LIGHT HAS THE BEST THROW. I AM NOT ASKING WHAT IS YOUR FAVORITE LIGHT.
Emitter size is not the only factor in determining throw.
Some emitters throw much better than others.
The two best throwy emitters are probably the SFT40 and the SBT90.2
One is better for smaller flashlights, and the other is better for larger flashlights.
It has???
Fireflies T9R
Astrolux EA02 / Mateminco MTY1
The larger the reflector and the smaller the LED, the harder it is to center. Plus, there is very little practical difference in intensity between Osram, SFT40, and SBT90.2; this means it is reasonable to select an emitter with higher output as the large reflector correlates with more heatsinking capability and battery capacity.
And yes, the intensity of a light is proportional to (output)(reflector frontal area)/(emitter area) by a fixed constant, with the constant being the intensity of a Lambertian emitter outputting 1 lumen.
The smaller the LED relative to the frontal surface area of the reflector, the more precise the reflector has to be to be able to focus the light in 1 direction.
For example, a dedomed Cree XP-C in a medium to large but cheap and imperfect reflector is impossible to focus in 1 homogenous hotspot.
This gets worse with a larger reflector
Maybe you’ve read about Enderman’s Siniosbeam.
He had a big parabolic dish made for a recoil thrower.
Electroformed reflector, very accurate, very expensive.
It was difficult to focus the thing, even with a XM-L size die.
So your idea is great, but it will be very very expensive to build.
The earliest batches of BLF GT with XHP 35 HI had a bit of inconsistency in the quality of the reflectors.
Some of them were not good enough and had to be replaced.
Professional search lights with short arc HID bulbs all have very expensive reflectors too.
But anything is possible with enough funds.
Interesting, will read about it.
A universal result of using a very deep reflector (short focal length) is that the spill angle is reduced. The spill is blocked by the reflector geometry.
If there is only one optic in the system, and the intention is to create a general purpose light, this probably is not desirable because spill is useful. But if the light consists of an array of optics, more along the lines of the big “lumen war” lights, then using deep reflectors will push the spill down range a little instead of it going directly onto the ground and into the air in front of the operator.
The deepest available reflectors manage to push the spill down range some 15-18 feet / 5-6 meters. It’s not a huge distance, but it’s probably preferable to the spill hitting the ground directly in front of the operator, when the output of the array is very high.
This is what I have observed so far without knowing much optics math - hope I’m in the ball park:
Same LED size, larger and deeper reflector (GT-FC40 in Convoy M21B-F-E): larger reflector has smaller hotspot (more “focused” with clearer border and smaller size) and less spill (smaller area and dimmer).
Same reflector size, with different LED sizes (Convoy M21B with B35AM vs GT-FC40): I am not sure about this one but the smaller B35AM LED has smaller hotspot. Not discussing output, just strictly the size of the hotspot. Also my Mateminco PD90S with the gigantic 11x10mm SFH55 LED has a very large hotspot despite of the deep reflector.
Combining small LED with deep reflector: great throw yes, but I believe this will result in small hotspot, limited spill. Perfect if this is a beam profile you’re looking for, but IMHO it’s unbalanced for general use. My favorite light? I prefer large hotspot and bright, large spill. GT-FC40 in M21F/E or SBT90.2 in Wurkkos TS30S. SBT90.2 doesn’t have a large hotspot but make up with 4000 lm output and 1 km throw.
Yup, this. The hotspot becomes too narrow for anything other than very specific uses, whatever they may be.
A bigger and/or deeper the reflector just means that it collects more light being cast off by the emitter.
Hotspot is what comes off the sides, hits the reflector, and gets bounced forward, ideally all as parallel rays.
Spill is what comes straight out and misses the reflector entirely.
Throw is purely the result of surface intensity. Dr Jones did the “proof” in an old thread.
That’s pretty much it.
I like the HS-802 because of the nice deep reflector which catches more light, but also pushes the spill farther forward so it’s not lighting up my toes as I’m shining up ahead.
The bigger and deeper the reflector, though, the more critical positioning the emitter to maximise the throw. Not just centering it in the hole for the X- and Y-axes, but also sanding/shimming to raise/lower the chip in the Z-axis as well.
An LED sitting flush on the mcpcb vs “floating” somewhat on excess solder, can affect the focus.
All that twitchiness makes for a light that’d have horrible QC if being mass-produced.
@ Lightbringer said—-
A bigger and/or deeper the reflector just means that it collects more light being cast off by the emitter.
Hotspot is what comes off the sides, hits the reflector, and gets bounced forward, ideally all as parallel rays.
Spill is what comes straight out and misses the reflector entirely.
Throw is purely the result of surface intensity. Dr Jones did the “proof” in an old thread.
That’s pretty much it.
—————————————
That Dr. Jones thread sounds like a good read , do you happen to have a link?
Thanks
.
Not offhand, but it’s still gotta be here.
@Lightbringer
Have not found that particular Dr. Jones thread yet ,but this one certainly relates relates to the OP’s question.
Ok few minutes later I found this , is this the Dr.Jones thread you are referring to?
Minor correction: a bigger reflector does not imply more light is collected: in fact, a large and shallow reflector collects less light than a small but deep reflector. What a bigger reflector does well is converting rays from a point source to near-parallel rays, the larger the reflector the closer to being parallel the rays are.
A really nice way to think about intensity is to imagine standing at the receiving end of the beam. What you see is a reflector filled with the image of the LED. Fixing the output constant, either an increase in reflector size or a decrease in emitter size results in the reflector making more "copies" of the LED, resulting in your receiving more light.
As Hoop said, the opening and depth of the reflector determine the angle of the spill. Secondly, the spill luminance is reduced as the emitter gets smaller.
Manufacturers have chosen this setup in the past. It’s very common in ‘tactical’ lights like Armyteks Dobermann (XHP35).
Yep sorry for that, that is the one I meant to plug in the there second time “a few minutes later”
Very interesting and informative thanks!
I do recall one member here modded their BLF GT with an Osram CULNM1 and I wasn’t very impressed with the range.
Here’s another mod with the BLF GT for 3,700m
The key to throw is focal distance from LED to optic.
A large optic has a larger distance to the LED.
So with a very deep reflector with a relatively small diameter, the distance between the LED and the reflector is still relatively small.
Yes, with a very deep reflector the distance from the LED to the widest part is relatively large, but extra depth only adds a little bit to how much light is reflected.
This is not worthwhile beyond 1:1 proportions of depth and width.
In fact, most LED flashlight reflectors are approximately 4 wide and 3 deep (like 40mm wide and 30mm deep or 60mm wide and 45mm deep) and even less deep reflectors can be found in throwers.
Extreme reflector depth mostly makes the head taller and more expensive and heavier.
One benefit can be that the spill is as narrow as the corona, eliminating much of the rainbow effect.
And in all more light is cast into a similar direction.
But if you want a tight piercing hotspot you need width rather than depth, and the spill will be more useful because it will be wider.
A 250mm diameter reflector and a 25mm diameter reflector may have the exact same focal length. These two reflectors will have the same parabolic geometry, except in regard to where the parabola terminates, i.e. where it is cut off. The focal length of a parabola is the distance between the vertex and the focus point.
A reflector with a short focal length may have the same linear distance from the emitter surface (focal point) to the clear aperture as a larger diameter reflector with a longer focal length. Example
