silence usually in china doesnt mean a bad thing, it just shows that until they have something to say they keep quiet, so i guess they are working on their own pace on this light and will reveal info when its time for it.
On one hand your right, but if your saying the spill light gets reduced because it’s put into the hot spot, that’s not right.
Removing the dome reduces lumen output everywhere (spill and hot spot). The amount of loss varies from emitter to emmiter, but let’s say 25% for example. Since the spill light is basically light shining directly forward from the led and not hitting the reflector, you will get a 25% loss in spill light lumens/brightness. I didn’t consider this a real loss earlier because all lumen output goes down by 25%, not just the spill. (Since it does change, I’ll go back and correct what I said earlier)
The dome creates a magnification effect, without it the actual smaller die tightens up the focus on the reflector creating a smaller hot spot. The hot spot has 25% less lumens, but due to being more focused, it’s lux/intensity/luminance overcomes this lumen loss making it appear brighter instead of dimmer. It’s the old “trade lumens for lux” scenario and is why the domes are added in the first place, to boost the lumens.
The extra intensity/luminance of the dedomed hot spot combined with the lumen loss in the spill gives a double whammy effect making it more noticable.
There is a whole technical description of how the dome creates a magnification effect, but I just rely on the simple concept below.
I’m sure there are some technical gurus on BLF that can go into way more detail on the dome effects.
If I misunderstood what you said, sorry about that.
I hear what you’re saying and appreciate the intended science but it just isn’t so. Can’t be. Taking the dome off does decrease overall output, but at the same time it nearly doubles lux. Hence, more down the middle. Given that there’s actually less lumens, the only way to get twice the lux is to take it out of the spill. I’ve seen that spill diminish way too many times… of course there’s more to it than the emitter itself, having the proper reflector is the other part of the equation. A light like the Solarforce Skyline I or the Jacob A60 nets a pencil beam with almost no spill, in much the same way an aspheric can tighten almost all the output into a hot spot. The devil’s in the details…
Check this picture.
The spill light is the orange/brown lines. It makes up very roughly 50 of the leds output (dependant on reflector size, etc…). Removing the dome can’t take spill light and move it into the main beam (the main beam created by the reflector).
Having a smaller point source (smaller die) can create a more parallel beam and can take some of the light from the coma or corona around the hot spot and put it into the main beam. This also adds to the increased intensity.
I really don’t know why certain lights can have almost no spill. Maybe the Lumen output from the LED is really low and the spill light is spread out really wide making it very difficult to see?
I never bothered to measure the intensity of the spill light when I switch from an HD to an HI (or slice a dome off). It never occurred to me to keep track of that.
Preaching to the choir brother, been at this for years and have done all the research. Closing in on 600 lights I think…
(being realistic I’ve forgotten virtually everything I studied, still building em though)
Alls I’m saying is that there’s theories and then there’s what happens when you build the light. Like I said, you measure 1000 lumens and 120 Kcd on a light, remove the dome and now it’s 800 lumens and 230 Kcd, how did you lose lumens but gain lux if it isn’t more focused? If it’s more focused more light is going into the hot spot and since we know there is less light, it has to be coming out of the spill, correct? Meaning what was once lost to spill is now focused into hot spot. Real world, no theory.
It’s actually in one of your pictures up there Jason, the dome magnifies the die surface so it appears much larger to the reflector, so less lux. The de-domed emitter shows a smaller apparent die surface to the reflector, hence a tighter hot spot. The reflector is focusing more of the light into the central beam. 
No, the lux is taken out of the hotspot, it has become smaller, it did not come from the spill. Because the hotspot has become brighter and the spill has not, the impression can be that the spill became dimmer.
You make it sound like there is science and there is the real world that does not care about science. This is incorrect and an attitude that is not helpful in any situation. Science does describe the real world (and often extremely correct and effective) , and can be very helpful also in our hobby.
DB, you forgot to also mention that the hotspot generally shrinks roughly in proportion to the lux increase. So if you gain 50% lux, the hotspot is usually around 50% smaller.
If you compress the light in the hotspot that much, it figures that the intensity would also increase.
In the end it doesn’t matter, if you take the dome off, you gain throw and loose lumens, this much we know for sure. How it gets there is not worth starting an argument over 
Hahahaha, I’m only saying I don’t understand the exact science, but I do know what works.
There is a given amount of light coming off the emitter. If the lux is caused to intensify, the spill has sacrificed it’s light into the hot spot. It’s not an apparent thing, it’s a real thing. 100 units are given, 80 to the hot spot and 20 to the spill. Change the die surface by de-doming (this is an apparent thing in relation to the reflector) and the 100 units is now 90 to the hot spot and 10 to the spill. See?
I have had far too many concussions to try and keep up with the science. My hands know how to make the light better, I just turn em loose…
Not arguing, discussing. 
That is alright :-), but being a former scientist it is very frustrating if people do not accept the one thing that will help them further in the world, so I’m a bit on a mission.
Huh?
Never knew.
Edit: sorry. Was rude asking this.
Another thing you guys seem to be forgetting is the angle that the light hits the reflector. The dome acts like a lens. One of the things it does is move more of the lumens to the center. That means more spill, since the central cone of light doesn’t hit the reflector at all. Taking off the dome allows more of the light to spread out more, hitting the reflector and then going down field in the hot spot.
Also, the index of refraction makes some of the light output from the die ‘look’ to the reflector like it’s coming from an angle different from the flat plane of the die. I suggest that’s also contributing to a larger hot spot and/or corona. When the dome is removed, the light comes out of the die and heads straight to the reflector at pretty much the angle the reflector was designed for.
These two effects might be small. But they are there and should be part of the equation, in addition to the conversations about apparent die size, lumens loss from de-doming, etc.
Jos, please look around… the vast majority will simply never get it. I used to sing-song to my children when they were young… You can lead a horse to water but you cannot make him drink, you can send a kid to college but you cannot make him think.
Perfection is a great idea, attaining it is impossible.
Science is the observation of our natural world. Dale isn’t denying science, he is practicing science. Mathematical calculations aren’t science, although the two are related, and science uses a lot of math. The “problem” with relying too heavily on math is that math requires absolute truth. Every ingredient has to be taken into account and measured accurately, etc. or the predicted result will be different from reality, as Dale has attested to.
I have drank an excessive amount of coffee in too short an amount of time, which causes me to get flippant and facetious. My bad. Sorry.
One thing I can’t wrap my head around is why a larger emitter results in lower cd.
I’m thinking about emitters in terms of lumens per sq/mm. For example, take the BLF GT and GT70. Let’s assume each emitter has identical output per sq/mm. The 70 covers the same footprint as the 35, plus more. It seems the 70 should have identical throw by covering the 35 footprint, plus more flood and total output based on the additional size. I don’t understand why the additional size interferes with throw.
The larger die is harder to focus and will never focus as well as a smaller die is part of it.
The other part is that large die LED’s generally have lower lumens per mm.
Thanks, TA.
Throw is determined by the intensity of the LED, not the overall lumens it produces. Think of intensity as lumens produced per square mm of die.
More intense LEDs will produce brighter hotspots that throw further.
Bigger LEDs usually (but not always) have lower intensity than smaller LEDS. However, bigger LEDs also usually produce more total lumens due to their larger surface area. In practice this means they have a less throwy hotspot… but the hotspot they do have is much wider.