Holy smokes. I had to read that several times before I understood what you said. And I'm kinda embarrassed to know so little about something I use everyday... Ie flashlights, TV's, laptops,
Having said that, are all xpg leds the same with different domes? (I.e tint/bins)?
If domes determine the color, is that why there is an aura around the hot spot of my light?
If so much energy is lost to heat, why don't we move the tint/dome further away from the emitter? Or use lens filters instead?
And if what you said about led spectrum is true, are modifiers removing the dome exposing a UV hazard?
The domes don't dictate the differences, they distribute what IS emitted....and aspects of that distribution impact some of those factors. (IE: You are focusing on domes instead of phosphors, confusing the issues)
The primary differences in tints, etc, are from the phosphors used.
So, for example, you would not have all xpg be the same with different domes, you'd have them all have the
same domes, and different phosphors.
The energy lost to heat is mostly from the electronics themselves, so you'd be moving the wrong part. (Again, the dome is not the important part) IE: You protect the LED by drawing heat away from the electronics, using heat sinks, fins, or whatever helps remove head from that part of the flashlight. The dome has ZERO to do with the heat management or effects of heat. Remember, the LIGHT from the LED is NOT the hot part, the electronics BEHIND the LED is the hot part.
Primary heat issue concept to get: For an incandescent light bulb, almost ALL it makes is heat, with a small amount of light...so, MOST of the energy put into an incan bulb is emitted as infrared radiation, with a small percentage being visible light. That means its mostly heat not light, and, the beam itself IS the hot part. For an LED, its MOSTLY making LIGHT not heat, so
the BEAM is not what's hot, its the electronics behind the LED.
The phosphors are what are shifting the UV to visible light, not the dome (Again, focus on the phosphors, the dome is not important, and, not protecting from UV, as the UV was converted to visible light by, yes, the phosphors...and, so, no, there's no real UV hazard from de-doming)
IE: The color, tint, CRI, are from the phosphors.
Energizing the phosphors uses energy...so, for any juice that flows INTO the LED, LESS LIGHT comes out, because MORE of that juice was used to make more phosphors emit the light at the desired wavelengths. The more you change the CRI, by using more phosphors, the less efficient the LED is at EMITTING light.
So, to get a higher CRI, you lose efficiency, lumens and cd, for any given drive level. (Its more efficient to produce some wavelengths, and less efficient to produce others....)
The "aura" around the hot spot is called the corona, and, its not because of the LED, its because of the way a reflector focuses a beam.
If you've ever played pool, or had to ricochet something, you've possibly noticed that things tend to bounce in complimentary angles...IE: They bounce off at the same angle they impacted at.....straight down gives straight back up (Dribbling a basketball), if you bank a pool shot off a bumper, if you impact the bumper at 15º, the ball bounces off it 15º to the other side, etc....And, when an LED, or bulb, etc, emits light, inside of a reflector bowl, the light is not ALL from the exact same POINT in space, its emitted across the entire surface of the LED.
SOME of the light will be emitted from a point on the LED that ricochets exactly dead center of the beam, and, as you move farther from that perfect spot on the LED, SOME of the light emitted will be LESS perfectly focused, and, NOT be centered in the middle of the beam. The light that's missing the perfect focus, but still gathered by the reflector and sent down range, has the best focused light in the middle, with a donut of less focused light around it. There will also be some light that missed the bowl entirely, and was not focused at all, it just spilled out of the bowl w/o hitting the reflector at all. THAT light is called the spill.
So a normal beam is composed of a hot spot in the middle, surrounded by a corona, with some spill outside of the focused beam.
This is NOT an artifact of the LED per se, in that all LED, bulbs, etc, form this pattern due to the REFLECTOR. (The SMALLER the LED, the easier it is to have MOST of the light it emits come from a point in space closer to perfect focus, and, that's a primary reason a smaller LED can throw farther for the same lumen output....the light is easier to focus. This concept is also referred to as apparent surface brightness, as the reflector "Sees" more light coming from a smaller surface, so, for the same lumens, its going to have higher lux.
Part of a dome's function is to distribute the light emitted by the LED, so it hits the reflector in a way that they thought would appeal to users.
The primary reason that modders REMOVE the dome, is because they want a tighter beam, to throw farther, and NOT the broader beam that the light's maker thought the general public would want. Losing the dome tends to reduce the flashlights' published lumens, which the marketing departments are loathe to do...as the general public has no clue what lux is. Removing the dome increases the apparent surface brightness of the LED, which increases the light emitted closer to perfect focus for the hot spot, but, which reduces the peripheral light that counts towards total lumen output.
The "Hole in the middle of the beam" pattern you see with a poorly focused beam, is typically the shadow of the emitter, as that requires a HOLE in the bowl (The emitter sticks out into the reflector through that hole...). A well focused beam refocuses light to fill in that hole, centering the hot spot in the center of the beam.
I hope this is a starting point for you to get a handle on the concept, and, let go of the dome-based misconceptions.