Is it that hard to focus a XML emitter?

As manufacturers upgrading their lights to use xml, I have realized that their old models being a thrower, the upgraded models are becoming floodier because of the xml. I guess there is a saving of not having to redesign the reflector and just shuff a new led in to make an upgrade model. Instead, it seems like they are using the brute force higher lumens to compensate for the reduced throw, which a lot of times result in the newer model having less throw but with higher lumens rating.

Is it that hard to redesign the reflector with the xml so the end result is to keeping or increasing the throw on a throw light? Or are they just being cheap?

that's just the way larger emitters are. the larger source point of emitted light means there is a smaller concentration of light w/ which to begin. most companies i'm aware of are redesigning their reflectors to optimize the focus of whatever emitter they are incorporating into their product line but the larger the light source, the greater the limitation as to the degree of which the light can be focused. larger emitters, larger hotspots...its simple math.

Yeah - unfortunately the parabola which describes how a point-source of light will reflect gets muddied as you stick bigger sources of light in there that resemble a point less and less. The best point source of light I can think of is an axial mounted HID. That can take 1000 lumens and hurl it easily over 1/4 mile to birghtly illuminate what you are looking at. Take a XM-L and try to get that far with the same size relfector and it won't happen. It takes a wider reflector to really concentrate the lights from a bigger LED and a deeper one to reduce the spill. This is why (IMO of course) lights like the TK21 and TK35 do really well with the XM-L and a very functional. They use a wide but relatively shallow reflector so you get a tighter spot and big spill.

It's really taken me down the road of having indoor lights and outdoor lights. I use pocketable more floody light indoors where illuminating a space is more important than throw. Outdoors I take a light with a bit more throw and let it do it's thing.

Well, I am seeing that emiters are getting bigger for flashlight for more lumens. Does that mean we are going to see less and less throw lights even the preceeding models were designed as or perceived as throw lights?

when manufactures come up w/ a new style of emitter (ie the XP or SST series) it is commonplace for them to make a second or third version w/ a larger die. this way they are increasing output but are still using the same basic technology. its a way to develop a new product w/ minimal R&D expense.

aau007 said:

Well, I am seeing that emiters are getting bigger for flashlight for more lumens. Does that mean we are going to see less and less throw lights even the preceeding models were designed as or perceived as throw lights?

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It's why I like the old XP-E/XR-E(better throw).

The bigger the die the smaller its reflector is in proportion.

At this point I'm in the "time will tell" mindset. The Cree XM-L is a fantastic LED for flood applications, but not ideal for long-throw applications. For me the XM-L is a dream come true, since I have no use for a torch that throws like a lazer...I need torches that just bath everything in front of them with a massive amount of smooth usable light. I am sure the people at Cree are pounding away at how the get more and more effenciency in a smaller emitter. The XM-L is by no means a "Do-All" emitter. Where is shines (pun intended) is in area illumination, giving us flood junkies an emitter to go nuts over. Perhaps the next emitter Cree comes out with will be more of a delight to the throw junkies. Just because it is the newest/brightest, does not mean it is the best choice for you. I don't feel that the companies are being "cheap", they are just designing to the emitters strengths instead of trying to "make a round peg work in a square hole".

stallion2 said:

when manufactures come up w/ a new style of emitter (ie the XP or SST series) it is commonplace for them to make a second or third version w/ a larger die. this way they are increasing output but are still using the same basic technology. its a way to develop a new product w/ minimal R&D expense.

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Animalmother said:

It's why I like the old XP-E/XR-E(better throw).

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But I believe lumens per square mm are still higher in the XR-E than either the XM-L or Xp-G.

Although, I must say the XML is better than the SST lights for throw. The SST50 is similar in output (maybe a tad more) but the XML is more efficient and cooler, with a smaller die so it kind of bridges the gap between the XPG/XRE s and the SST lights, IMO.

For focused lights i also prefer xr-e/xp-e. The light don't need to be huge to throw, and it uses way less juice to do the job.
I like the xm-l in a tiny light like the minix. Gives a huge hotspot that is exellent for general stuff.

dosei-45 i think you would like a triple xpg, it will send you to flood hog heaven

The same complaint was often made when companies started converting lights from XR-E to XP-G (And to a lesser extent, XP-E) LEDs. Eventually we started seeing new lights designed for the new emitters that got decent throw... I just wish that more optics are being used to get throw without a huge head to hold a big reflector. A good light with an XR-E might still be a good light with an XP-G dropped in and no other changes, but it won't be the same light.

xpe will focus better and has nicer tint. well thats been my experience.

to focus an xml you need a bigger reflector. a big badass reflector.

aau007 said:

Is it that hard to redesign the reflector with the xml so the end result is to keeping or increasing the throw on a throw light? Or are they just being cheap?

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yowzer said:

I just wish that more optics are being used to get throw without a huge head to hold a big reflector.

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The LED emitters may be reaching the ceiling in their development?
The LED emitters are getting larger in size, to increase efficiency, and produce more light, as the XP-G and XM-L does.
However, their surface area is increasing at a much greater rate than their lumen output.
The XR-E R2 is roughly 1mm x1mm.
The XP-G R5 is roughly 1.2mm x 1.2mm.
The XM-L 2mm x 2mm.
SST-50 2.25mm x 2.25mm.
Thus, their maximum surface brightness is decreasing.
Surface brightness is the main factor in determining the throw.

To compensate, a large diameter reflector can "capture" more light, and focus that light into the hotspot, to produce a brighter and more intense hotspot to increase the throw.
Because the XM-L has a reduced surface brightness, if we increase the diameter of the reflector to capture more light, and focus that light into the hotspot, then we can further increase the intensity of the hotspot to produce more throw.
This is how the Olight M3X XM-L, the Eagletac M3C4 XM-L with 394 meters throw, and the Thrunite Catapult V3 XM-L with 402 meters throw works - as measured by Selfbuilt.
M3X http://www.youtube.com/watch?v=ASH0WXioYe8
M3C4 http://www.youtube.com/watch?v=RpyyIFWMT7c
Catapult V3 http://www.youtube.com/watch?v=y8YwnsBExIM

In the videos above, note how the Catapult V3 has a narrower spill, yet a much brighter "corona".
So if the reflector diameter remains the same, while the reflector depth increases, we say that the depth to diameter ratio increases.
A deeper reflector ratio diminishes the width of the side spill.
However, a deeper reflector ratio also causes something like "diffraction" of light to occur, creating an additional band of light around the hotspot called the "corona".
A deeper reflector ratio will not give more intensity of light in the hotspot, nor more throw.
A deeper reflector ratio increases the corona.

The spill, is light that fall directly on the surface, from the emitter itself.
The brightness of the spill is determined directly by the brightness of the emitter.

One advantage of a larger die size of the XP-G and XM-L is that it does give a larger hotspot.
A larger reflector diameter does not result in a larger hotspot, but a brighter hotspot.

Summary:
Thus the die size determines the hot spot size.
The die surface brightness determines the brightness of the hot spot, hence the throw.
The reflector diameter collects the light and focuses it into the hot spot, to further increase the brightness of the hot spot, and hence the throw.
The reflector depth to diameter ratio actually makes the side spill narrower, but increases the "corona" - an auxiliary band of light surrounding the hot spot.
The lateral spill of light, comes from light that is falling directly from the emitter itself, thus the spill brightness depends on the emitter brightness.

If we calculate the surface brightness of many flash lights, we find that the surface brightness is actually very close.
For example:
Olight SR90 SST-90 @ 2200 lumens divided by 9 mm sq = 244.44
Jb RRT-3 SST-50 @ 1200 lumens divided by 5 mm sq = 240
Eagletac M3C4 XM-L @ 1000 lumens divided by 4 sq mm = 250.

With such similar surface brightness, how do we explain the SR90's 634 meters of throw, versus the M3C4's 394 meters of throw, according to Selfbuilt's data?
What really determines the throw in these lights is actually the bezel and hence reflector diameter.
For example, the SR90's bezel diameter is some 100 mm, versus the M3C4 XM-L's 61 mm.

Thus to answer aau007's question, it is actually very easy to redesign the reflector for the XM-L emitter, but you will end up with a larger diameter reflector to compensate for the fall in surface brightness of the XM-L emitter!!!

For yowzer, with present technology, an XM-L emitter with reduced surface brightness, given the same size diameter reflector, it won't be possible to maintain the throw, let alone increase that throw.

If an engineer could increase the brightness of the emitters, while maintaining the overall dimensions of the die, then he will be a rich man...

For more information on throw, you can search cpf, esp members like Saabluster, Dr Jones, Ra, walterk & gcbryan - they understand this complex topic very very well.
I've never been able to get past the first few sentences of their complex science articles...

I think an important question to ask is if it is a goal of the LED industry to provide an LED with greater surface brightness than is currently available, or just a LED which is more efficient overall? I would be willing to bet that Cree and Luminus have not designed the XR, XP, XM and SST LEDs with only a flashlight in mind. There is much more money to be made in home illumination, car running/headlights, etc.

Maybe I am wrong, but it seems to me flashlights are just a side use of these LEDs.

Presently, the 2mm x 2mm XM-L emitter can be driven to 3 amps to produce 1000 lumens.
If they could increase the efficiency by 20%, then the 2mm x 2mm XM-L @ 3 amps will output 1200 lumens - a simultaneous increase of both 20% in surface brightness, and 20% in efficiency.
However, if they need to drive the 2mm x 2mm XM-L to 5 amps to produce the 1200 lumens, then they have increased surface brightness, but they have actually decreased the efficiency.

Yes, I think LED design is more focused on serving domestic, commercial & industrial use, rather than maximising throw for our flashlights - thus the current batch of emitters are not very suited to increasing the throw.


The Surefires may prefer tunnel throw to suit rifle scope illumination, and the limited lateral spill minimises alerting the enemy.

Personally, I think both throw and flood are important.
I think we must have both designs, and not just one or the other.
The flood and throw designs must sell along side one another just like soft luxury sedans, and firm sports car suspension options.
Imagine a world where all cars were soft, and firm suspension was no longer available?

ITPython said:

However, up until now the market has been pretty much saturated with nothing but tunnel-throwers, so it's nice to see lights finally starting to utilize good flood.

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+1

Actually, I think that having both flood and throw ends up with a light that isn't that great in either regard. I generally need flood and sometimes need/want more extreme throw. That's best done with two lights IMO.

Yes, we must have two separate flashlight designs in two separate flashlights models like the SR90 & SR92, or the Eagletac M3C4 XM-L and M3C4 Triple XM-L etc, like a Mercedes E350 Elegance [for luxury], and an Avantegarde [for sports] etc...

aau007 said:

Well, I am seeing that emiters are getting bigger for flashlight for more lumens.

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There have always been bigger emitters around since I joined CPF in 2004.
At that time the luxeon V emitters were the big ones (actually comprising 4 luxeon I dies).
As time progressed they were followed Seoul-SSC-P7s, Cree-MCEs, Luminus SST-50 and SST-90 and now Cree XM-Ls.

In fact the Cree XM-L is smaller than the earlier SST-50 whilst being more efficient at the lower current range that most flashlights are driven at. (ie anything up to 3 Amps)

At the same time there are many smaller emitters around to choose from:-
Cree XRE's/XPGs/XPCs/XPEs, lumileds rebels/luxeons, Nichias, Seoul SSC-P4 etc.

We actually have far more choice now than we used to.

aau007 said:

Does that mean we are going to see less and less throw lights even the preceeding models were designed as or perceived as throw lights?

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There are options available for whatever type of light we want:-

a) Large emitters in large lights when we want powerhouse, search and rescue type light.
b) Small emitters in large lights when we want dedicated throw (without much spill).
c) Small emitters in small lights when we want edcs that can throw a little.
d) Large emitters in small lights when we want edc flooders.