Brightness, is the total light. To get an idea of total light point the light at the ceiling and measure lux on the floor next to the light. It will be less with your mod.
The reason it throws further is because more light gets focused into on spot.
Here a diagram is.
Notice how before there are 9 beams before and 7 after. Yet the after one would clearly light up things further away, despite there being less light.
Yea, as people mentioned the brightness is about the same besides losing some through your device. If you did a ceiling bounce test, the room would stay about the same brightness whether you had your device on it or not because the lumens from the emitter remains the same. While the hotspot becomes brighter, your spill becomes dimmer.
This thread is very confusing and filled with misunderstandings. Take your time and read the truth here:
Brightness -Wikipedia
and here:
Luminance -Wikipedia
Is this the same concept as why an XP-G can outthrow an XM-L with superior lumens?
It is what happens, but is not why. The reason the XP-G can throw further is the smaller die size, so it is closer to a point source of light. So what matters for that is lumens per mm2. Which is where the XP-E2 wins, but then you have to take into account the beam angle which is narrower on the XR-E which could be beneficial with aspheric lenses, but is detrimental with reflectors.
XPGs can throw further because the surface area of the XPG die is 1x1mm while that of the XM-L is 2x2mm ie, four times as large. Reflectors in a different way from aspherical lenses project an image of the die forward so the smaller the die, the smaller the size of the hot spot.
Geeeezus people…for goodness sake can we just agree the light does appear brighter?
let’s not throw lumens or candela or scientific formula into how to calculate the brightness into this mod.
it is what it is… the lux meter show it’s brighter and that’s good enough for me even if it still the same lumen.
what i’m trying to achieve here …is to use a cheap and decent light and turn it into something of more expensive thrower
the mod does create a brighter hotspot, the same hotspot of more expensive light that cost 10X more expensive.
of course as we know it… to get throw, you will sacrifice spill, you can’t have the throw of TN31 with the spill of TR-J18.
so let’s us all just agree that the mod gives a better illumination than before.
if there’s no pictures to back it up… then all is just words 
Is that it? I thought that the problem was since optics are designed for a true point source anything not in that point is not going to go perfectly "Straight" and will diverge from the beam. Then the higher lumens per mm2 of the XP-G will make it throw further.
For example the XP-G2 die produces 86.73 lumens per mm2 while the XM-L die produces 45.5 lumens per mm2.
lol… good one
No...
You don't understand. If it can't be dissected, corrected, manipulated, stipulated, debated, rejected or accepted, it can't be discussed in a flashlight forum.
Yes, you redirected the light and it appears brighter, because it is more focused. No, it really isn't brighter scientifically, because optics cannot increase light output. They are all just going through their usual long BLF process, let them enjoy, they can't help it.
As for me, I think it's a pretty cool attempt at focusing the light from your flashlights into a more usable beam. Not everyone knows the scientific correctness and the reality is "It's just a flashlight for ***** sakes and it's just a hobby, not building a rocket here, LOL. Have fun with it.
It sure looks brighter on my ipad.
cheers 
Guys, the argument here is over terminology. It technically is not brighter as brighter is total light output. It is throwier which is the amount of light in one point which is what the lux meter measures.
woo hoo i got one to agree with me … cheers
it actually IS brighter, in the part that matters to the OP. He took useless spill that was being wasted, and focused that light into the main focal beam, making it brighter than it was before. Thats not science, its just common sense.
In an attempt to educate/give some insight on terminology, I think some people got a little “CPFish”. No harm no foul, just the flexing of flashlight knowledge muscle. But really, theres no need to troll the OP and flame the guys country and education system. 
Now, if he was from Kentucky…
I think you guys took all the excitement out of DayLighters cool invention and marginalized the whole spirit his experiment over the word “looks”.
Since the US hasnt brought anyone to the moon since 1972, does that mean that US citizens have become less educated?
Cool contraption daylighter,those lenses look to be from a projection tv.I have pulled some monster lenses from them myself.It's always fun to experiment with stuff like this and many great ideas are born that way.