# What does dedoming mean?



## look171 (Aug 7, 2013)

If its performance is so great, why doesn't flashlight or LED mfg do it?


----------



## bshanahan14rulz (Aug 7, 2013)

http://www.philipslumileds.com/products/luxeon-C
http://www.luminus.com/products/SBT-90.html

not quite the same, but
http://www.cree.com/led-components-and-modules/products/xlamp/discrete-directional/xlamp-xqb

Your thread title is misleading. It would seem that you DO know what dedoming means ;-)
Generally, it is avoided in order to allow more light to escape the package, instead of being reflected off the dome/air interface. A dome is a way for more light to hit that interface surface at a close to perpendicular angle to cut back on internal reflection. Kind of like how you can see an image reflected on a piece of clear glass at shallow angles. You see that image because the light is hitting at an angle that is so shallow that it no longer wants to go through the glass, but instead wants to reflect off of it.

http://en.wikipedia.org/wiki/Snell's_law#Total_internal_reflection_and_critical_angle < here's more information for you


----------



## RoGuE_StreaK (Aug 7, 2013)

From my limited research recently, it seems fair to say that overall performance _decreases_, but for some applications, specifically behind thrower lenses, it works better because it gives a smaller apparent die; the die brightness drops a bit due to the reasons listed above, but as it's now occupying a smaller (apparent) space the brightness per mm2 (or some term like that) actually increases.
In short, for aspheric throwers de-doming supposedly yields higher output, but for most other applications the performance is actually lower.

I've been trying to decide whether to buy a cheapie zoom-to-throw XM-L torch, as I'd read that XM-Ls are by no means the best behind a lens; trying to figure out if de-doming would give an $8 monster thrower or whether even ye-olde XR-E would outgun it.


----------



## Norm (Aug 7, 2013)

look171 said:


> If its performance is so great, *why doesn't flashlight or LED mfg do it?*



The question in the op is bolded, I think the OP understands the whys and wherefores.


----------



## RoGuE_StreaK (Aug 7, 2013)

Weird, it doesn't show up bolded here. And woulda thought the whys and wherefores answer the why nots?


----------



## Grmnracing (Aug 7, 2013)

RoGuE_StreaK said:


> Weird, it doesn't show up bolded here. And woulda thought the whys and wherefores answer the why nots?



No bold when using the Tapatalk app for me.

Reminds me of the good old days when I would get in trouble for large pictures by using the Tapatalk app.


----------



## Norm (Aug 7, 2013)

As Bolded in my quote.

Norm


----------



## light-wolff (Aug 7, 2013)

look171 said:


> ...why doesn't flashlight or LED mfg do it?


Because it essentially destroys the LED. Bare chip+phosphor coating exposed to the elements, oxygen, humidity.
The protective dome is there for a reason. No serious mfg would ever even think about removing it.
It's like selling peeled apples.


----------



## TEEJ (Aug 7, 2013)

light-wolff said:


> Because it essentially destroys the LED. Bare chip+phosphor coating exposed to the elements, oxygen, humidity.
> The protective dome is there for a reason. No serious mfg would ever even think about removing it.
> It's like selling peeled apples.



LOL

So the ones selling LEDs with no dome to improve throw are overstating the expected life times?

I'd bet you that the dome is there to spread the beam out so it hits the reflector the way it describes in the wiki references above...not to protect it.

No dedomed lights have degraded over time that I have at least.

The humidity can still get in from the led side of the board, and so can airflow with oxygen, etc.

When it heats up, the air inside expands, and vents. When it cools, it sucks air back in...its not hermetically sealed with a vacuum, etc.




In a nut shell, the lights for consumers assume that the consumer will want a certain OTF lumen # as a primary shopping criteria if they are using specs and not how "tactical it looks, etc".....and a round regularly shaped beam w/o artifacts is desirable for most of them....and when sold in REELS of LEDs, the domes do help to prevent direct contact with the LED itself during shipping/production/assembly, etc.

So, when we want to make the beam project straight out more and concentrate the hot spot, more than we want it to have more spill/corona, etc...we can remove the dome and the lumens may drop a bit, but, the ones that are left do march straight out much better.

A floody beam, overall, is more useful, so, Joe Consumer may not want to make that trade off. Joe Thrower might want to though, and that's who dedomes. 

Or you can just buy LEDs made w/o domes to do the same thing, such as the SBT's already linked to as examples...so you don't have to pop off a dome.


----------



## melty (Aug 7, 2013)

RoGuE_StreaK said:


> Weird, it doesn't show up bolded here. And woulda thought the whys and wherefores answer the why nots?



Emphasis was added by Norm. There is no bold in the OP.

To answer the original question:

Why don't LED manufacturers sell LEDs without a dome? Flashlights are a teeny-tiny-itty-bitty piece of the LED market. Throwy flashlights are a teeny-tiny-itty-bitty piece of the flashlight market. The market for LEDs with no dome is so incredibly small that no manufacturer would ever consider selling them that way... for all practical purposes the market doesn't exist to them.

Why don't more flashlight manufacturers use de-domed LEDs? Most likely because it's too expensive (and temperamental) for the relatively small gain in throw. Since LEDs aren't manufactured without a dome, it means they _have_ to be removed by the flashlight manufacturer. I'm guessing that if any of these Chinese manufacturers were willing to de-dome, it would be incredibly expensive. Hobbyists and super-specialized flashlight makers are the only ones left.

This is all conjecture, but that's how I understand it.


----------



## SemiMan (Aug 7, 2013)

As pointed out, MFRs do sell them. They are used in situations where high levels of optical control are needed. I.e. theatrical spots, specialized architectural, etc. No dome does not mean it is not sealed, it just does not have a full dome.

Semiman


----------



## light-wolff (Aug 7, 2013)

TEEJ said:


> I'd bet you that the dome is there to spread the beam out so it hits the reflector the way it describes in the wiki references above...not to protect it.
> No dedomed lights have degraded over time that I have at least.
> The humidity can still get in from the led side of the board, and so can airflow with oxygen, etc.
> When it heats up, the air inside expands, and vents. When it cools, it sucks air back in...its not hermetically sealed with a vacuum, etc.


I was thinking of dedomed XM-Ls (this is very popular in the German flashlight crowd).
XM-L (and all other CRE LEDs) domes are basically glued to the emitter. They ARE sealed. People use solvents to remove the dome. Pulling off the soften and partially dissolved dome stresses the phosphor coating and the wire bonds, somtimes ripping them off. I wouldn't trust a LED that was subjected to this kind of treatment. Plus you never know what the solvent does to the phosphor.

Luminus is different: the domes aren't attached to the chip, but to a frame, and the chips are not selaed (maybe this is one of the reasons for their rather poor lm/W?). Removing the dome on these doesn't do anything to the chip, agreed.


----------



## Harold_B (Aug 7, 2013)

Without a dome and de-domed would be two different things to me but then the differences have already been pointed out. Here's a couple of my favorites that were not mentioned:

http://www.philipslumileds.com/products/luxeon-z
http://www.philipslumileds.com/products/luxeon-z-es


----------



## argleargle (Aug 7, 2013)

It wasn't so long ago that I didn't know what the heck a de-domed emiiter meant!

This is, IMHO a fantastic thread! A clear dome over a LED emitter changes its beam characteristics. As has been stated in the thread, it most definitely plays a role in protection of the product while shipped in the logistical requirements of the manufacturers. That bare thin phosphor layer can't take much abuse when bounced around in shipping or what not. If completely protected already in a sealed flashlight head, it might not be so big a deal. As far as I have read and understand, the only de dedoming reason would be honorable and noble flashlight hackers who are trying to create the next generation of ultimate tight-throwing flashlights with whatever is on hand or available by part number.

Then again, maybe I don't know what I'm talking about. Were you really going to try soaking your emmitters in gasoline or acetone? This action by it self? I am sort of an old-timer. I recall an internet hoax about coating your computer modem in wax to make it go faster. For your newcomers, this is the thing that let you get on the internet once-upon-a-time.... with your phone land line. Anyway, I see a real purpose for de-doming. It's for the high end flashlight hackers and flashaholics seeking the ultimate long range throw with whatever parts they can get. We don't give a flip about what can be done 5 years from now. We want it now. Joe Flashlight doesn't need or want it because it introduces too many variables for a non-enthusiast to want.

Put it this way, would you strip the heatsink off of your computer processor because someone told you it would simply make it go faster? In the 386 PC processor days, that would be 100% fine, but it wouldn't have an effect. PC cpus didn't even have a heatsink back then, except for the newfound world of "overclockers." It was arcane magic back in those days, there wasn't a guide on Tomshardware, Anandtech, or HARDOcp to tell you how to do it. Oh wait, I didn't check to see if those sites even still exist! Anyway, those sites came later in the PPP-internet connection days. It was far from the text-only SLIP-unix days. Telnet and lynx? It is far from that simple, friends. It's far from that simple. It's related, however! Electrical engineering doesn't change much, it's just the components that get better! Emacs versus VI? Domed versus de-domed? Is it the same holy war without an understanding of the underlying architecture?

You're mostly exposing the reactive phosphor layer to open air and any contaminants that can get to it. If you had a hermetically sealed and nitrogen purged flashlight head, it should probably be okay... theoretically. Ever heard about nitrogen-purged rifle scopes? It's sort of the same problem and same solution. You *DID* know that phosphorous is used in MATCHES, right? Did you really want this to get super-hot in an oxygen environment? Are you seeing dark spots on the phospor layer of your emitter die? Is the light itself turning blue? People like me remeber the revolution that happened when white 5mm leds became possible. It was a brilliant hacker who CHEATED to make it happen. Everyone wanted a white led and all attempts failed. He made it work by "cheating" and using a blue emitter to blast a custom phosphor layer... it's something we take for granted these days.

I'm sorry. My lawn is full of holes. I try to tell people to get off of it, but I can never seem to do so in time. My poor lawn is half dead.

My lawn.

PS: CPF, I'd quit ya, if I only knew how, younger sister!


----------



## RoGuE_StreaK (Aug 7, 2013)

I'll have what he's having! :buddies:

How about concave, um... _un_domes? To make the die look smaller again? :thinking:


----------



## SemiMan (Aug 7, 2013)

If he was younger I would call him Anders.

Sent from my Nexus 4 using Tapatalk 4


----------



## Bullzeyebill (Aug 7, 2013)

Alright guys, be nice.

Bill


----------



## argleargle (Aug 8, 2013)

RoGuE_StreaK said:


> I'll have what he's having! :buddies:
> 
> How about concave, um... _un_domes? To make the die look smaller again? :thinking:



Now THAT sounds interesting! I remember back when people said *you couldn't have a negative refraction* on normal materials.

http://en.wikipedia.org/wiki/Negative_index_metamaterials

A bunch of old men said it couldn't be done. Just to spite them, some youngsters went and did it. I think that they said it just to make some young interns work past their pay grade. The best part is they pulled it off!

TL;DR summary? Those darned kids made a flat lens that shouldn't exist. Good on them!!!

Wake me up if there's a flashlight that uses negative metamaterials and LASER COOLING. While we're at it, why don't we crack how some tech companies managed direct laser excitement of a phosphor laser? It's like a white LED minus the blue LED component, simply using laser light to excite the phosphor layer!

Oh wait... http://www.candlepowerforums.com/vb/showthread.php?352543-Remote-Phosphor-Formulation

When did THIS happen? This is good! I want more stuff like this!

Here's an intro to laser cooling. http://hyperphysics.phy-astr.gsu.edu/hbase/optmod/lascool.html
Basically, you shine a certain kind of laser on a certain substance and it LOWERS IN TEMPERATURE! All it does, really, is move the heat from one part of the design to another. My understanding is that is defeats Peltier coolers at this time.

Did you want the brightest light yet, or what? ... or did you just wonder what this "de doming" thing meant?

I tell you, I'm getting older by the second. I just noticed that my hands looks like gloves typing in the darkness from the light from this newfangled LED-backlit thin screen monitor. My first monitor was green monochrome CGA... later I got one with a switch on the back that let me have 16 color graphics. They called it... EGA. I remember when VGA came out.* It would blow a fuse* in my EGA monitor if I accidentally tried to run a VGA protected-mode application.

I'm going to go put some lotion on now... or something. I really can't be this old yet. Once upon a time on some linux forums, people said I was an elf! I didn't know at the time that they were insulting me and comparing me to the HAARP project and the conspiracy theories out there. So what if the Earth resonates at a natural frequency that was named after that Schumann guy. http://en.wikipedia.org/wiki/Schumann_resonances

Really, though... my lawn is in shambles. I hired some people to cut it with their high-tech zero-turn radius mowers. One got STUCK and the other had to pull him out with a chain. It was horrible. I have ruts all in the east side of my lawn from that... dead grass everywhere!


----------



## psychbeat (Aug 8, 2013)

This thread rulz!

Both of my dedomed XML2 lights throw quite well & I've used one in the field extensively without any issues. 

The tint can get a little green if u start with a cool white i think but my dedomed 4000K looks VERY similar to a 3200K hiCRI. 

Ok back to lawnmowers & lotion!


----------



## LEDealer (Aug 8, 2013)

Cree XQD is UN-domed, not DE-domed. In fact, all of these products are UN-domed.

It doesn't make sense for a manufacturer to make an LED with a dome and then TEAR IT OFF! That's just silly! 

Undomed products generally have superior color over angle as compared to the domed versions of the same part.

In the Philips LumiLEDs domain for example, LUXEON Z ES has better color over angle than the LUXEON T, which is just a LUXEON Z ES with a dome...


----------



## Harold_B (Aug 9, 2013)

"In the Philips LumiLEDs domain for example, LUXEON Z ES has better color over angle than the LUXEON T, which is just a LUXEON Z ES with a dome..."

LEDealer, Interesting. Link to data? Are you certain the Z ES and the T are using the same phosphor deposition process or is the Z ES more similar to the Rebel ES?


----------



## bshanahan14rulz (Aug 9, 2013)

I wouldn't be surprised if the "undesirable" wavelengths are getting "filtered" out by internal reflections on the flat faced packages. My guess is that since at a very acute angle to the surface of the die, light emitted at this angle has a greater chance of being down-converted because it has to travel through a thicker path of phosphor, hence yellower light rather than the tint of light going more forward from the LED.


----------



## LEDealer (Aug 9, 2013)

Harold_B said:


> "In the Philips LumiLEDs domain for example, LUXEON Z ES has better color over angle than the LUXEON T, which is just a LUXEON Z ES with a dome..."
> 
> LEDealer, Interesting. Link to data? Are you certain the Z ES and the T are using the same phosphor deposition process or is the Z ES more similar to the Rebel ES?



I am pretty sure. Just look at the footprints! They don't match the Rebel parts.

To me, Z ES looks like the building block for many of the products in the Philips line of LED products.

The S,M,T all look like they use a Z ES. I'm actually surprised that they haven't just released all of the possible versions of their products.

If you see them next to each other, you can tell they use the same basic parts combined in different ways to make the others.


----------



## Harold_B (Aug 9, 2013)

Not to side track the thread too much but in the spirit of discussing non-domed product....

My understanding from the Philips reps is that it is not the foot print but the die geometry that will tell you if the product is from the same basic design family. I do think that most of the Luxeons share the same die depending on size but Philips does have a couple phosphor deposition technologies that perform differently. That was why I was wondering if you had a link or data so that I might be able to see which is which. Of the single die LEDs I'm pretty certain the Z and the Rebel, and the Z ES and Rebel ES share emitters. I have S, M, Z's and lots of Rebels on hand, and Z ES and T's on the way. Not all are white though so I can't be certain about the color over the viewing axis. I know Philips publishes the data plot for several of their LEDs but it is in a separate spec sheet.


----------



## ianfield (Aug 11, 2013)

bshanahan14rulz said:


> http://www.philipslumileds.com/products/luxeon-C
> http://www.luminus.com/products/SBT-90.html
> 
> not quite the same, but
> ...


 Its about beam angle - a wide angle LED has an almost flat lens.


----------



## SemiMan (Aug 11, 2013)

Harold_B said:


> Not to side track the thread too much but in the spirit of discussing non-domed product....
> 
> My understanding from the Philips reps is that it is not the foot print but the die geometry that will tell you if the product is from the same basic design family. I do think that most of the Luxeons share the same die depending on size but Philips does have a couple phosphor deposition technologies that perform differently. That was why I was wondering if you had a link or data so that I might be able to see which is which. Of the single die LEDs I'm pretty certain the Z and the Rebel, and the Z ES and Rebel ES share emitters. I have S, M, Z's and lots of Rebels on hand, and Z ES and T's on the way. Not all are white though so I can't be certain about the color over the viewing axis. I know Philips publishes the data plot for several of their LEDs but it is in a separate spec sheet.



The Rebel ES is a larger die version of the Rebel is it not, similar to the Cree XPG/XTE relationship. I am looking at a Rebel and ES and the die looks bigger.

Semiman


----------



## LEDealer (Aug 11, 2013)

SemiMan said:


> The Rebel ES is a larger die version of the Rebel is it not, similar to the Cree XPG/XTE relationship. I am looking at a Rebel and ES and the die looks bigger.
> 
> Semiman



Here's the breakdown I got (had to go check my notes to make absolutely sure):

Z die = Rebel die

Z ES die = Rebel ES die = LUXEON R die = LUXEON A die = LUXEON M die (there are 4)

Rebel package and dome = rebel ES package and dome = LUXEON A package and dome = LUXEON R package and dome

T = Z ES with a dome and a frame

M = 4 Z ES on a frame under one dome

In other words, if you took apart a LUXEON T or a LUXEON M, you would have one or four Z ES devices.

BTW, the XTE die is bigger now than it used to be. That's why they are brighter now than before...


----------



## Harold_B (Aug 11, 2013)

Yup, we're on the same page regarding the Luxeon packages. The question I still have is color over the viewing axis and a link to the spec sheet or data. I'll keep searching myself but I'd hoped you had a handy reference. My curiosity is driven by an application so I need to support a selection with data. 

As far as the different phosphor application methods that Philips uses, a good example would be the Rebel ES and the R. Same die, same package. The R CRI is a minimum of 70 where the ES is a minimum of 80 and when I look at the packages they don't look the same even when selecting the same CCT. I'm much less concerned about this than the color over the viewing axis performance for an un-domed vs a domed LED.


----------



## bshanahan14rulz (Aug 12, 2013)

Optics can be used to mix colors from three separate dice into one optic. I've not seen one of these, but if they claim to have made one, that same principle should be able to mix the different white light coming from different angles, right?


----------



## outersquare (Aug 12, 2013)

Is there any sacrifice in durability/longevity after dedome? The lens seems to offer protection for the die wires and phosphor. 
I once used a replacement LED bulb for my car on the license plate light and it quickly died, I noticed it was because the LED type had exposed phosphor.


----------



## LEDealer (Aug 12, 2013)

outersquare said:


> Is there any sacrifice in durability/longevity after dedome? The lens seems to offer protection for the die wires and phosphor.
> I once used a replacement LED bulb for my car on the license plate light and it quickly died, I noticed it was because the LED type had exposed phosphor.



Those were probably very cheap midpower devices in a non-DOT retrofit headlamp.

Also, please see the above posts about "de-doming". The parts are UN-domed, meaning that they never have a dome to begin with. Hence, there is no issue with reliability after "de-doming" because that never occurs.

In addition, the Philips LumiLEDs parts don't have die wires. They are TFFC.


----------



## LEDealer (Aug 12, 2013)

Harold_B said:


> Yup, we're on the same page regarding the Luxeon packages. The question I still have is color over the viewing axis and a link to the spec sheet or data. I'll keep searching myself but I'd hoped you had a handy reference. My curiosity is driven by an application so I need to support a selection with data.
> 
> As far as the different phosphor application methods that Philips uses, a good example would be the Rebel ES and the R. Same die, same package. The R CRI is a minimum of 70 where the ES is a minimum of 80 and when I look at the packages they don't look the same even when selecting the same CCT. I'm much less concerned about this than the color over the viewing axis performance for an un-domed vs a domed LED.



While I can't quantify it, an un-domed part should have more total internal reflection resulting in better color over angle than a comparable domed product . This is because the refractive index of air is less than that of the silicone dome.


----------



## look171 (Aug 13, 2013)

Thanks so much but a lot of this technical stuff is way over my head. My extensive flashlight knowledge is to buy a Maglight with three batteries if I need a bright light. That's it. I read many post about de-domed LEDs or as one of you put it concave, so I ask a dumb question. Anders???? At least let me in on the inside joke.

So, basically a de-domed LED can result in a more focus beam in a thrower flashlight compared to a general wider beam? Is this why they de-dome them?


----------



## RoGuE_StreaK (Aug 13, 2013)

Yeah I thought your initial question was your actual question, not the reinterpreted question... 
Anders = a regular here who's posts are often outlandish/bizarre

In a nutshell, yeah, if you a dealing with lensed throwers (as opposed to reflectored throwers, which are different beasts). Removing the dome essentially makes the die look smaller to the lens than it does with the dome intact, resulting in the same(ish) brightness in a smaller area, which works better with the lenses for increased "throw".


----------



## SemiMan (Aug 13, 2013)

That applies to a reflector as well not just a TIR lens.

Sent from my Nexus 4 using Tapatalk 4


----------



## ILIKEFLASHLIGHTS (Aug 19, 2013)

There is no substantial proof that a domed emitter will last any longer than a de-domed one. And throw is about doubled on most emitters when the dome is removed. The dome is basically there to protect the emitter and keep it from getting wet or moisture in it.


----------



## SemiMan (Aug 19, 2013)

Ah no not really. A silicon coating is there for protection of the die, bond wires if they exist and phosphor, but its a dome shape for optical reasons. Non domed emitters exist but they still have a coating.

Semiman

Sent from my Nexus 4 using Tapatalk 4


----------



## LEDealer (Aug 19, 2013)

ILIKEFLASHLIGHTS said:


> The dome is basically there to protect the emitter and keep it from getting wet or moisture in it.




This little thing called "encapsulation gain" would beg to differ with your assertion. The dome does play a role in reliability, but its primary purpose is to increase flux, i.e. optical considerations.


----------



## ILIKEFLASHLIGHTS (Aug 20, 2013)

Well a de-domed emitter will last a long, long time if driven just like a domed one. The gain in throw is dang near double and well worth doing if throw is what you are wanting.


----------



## argleargle (Aug 20, 2013)

OT comments removed. --Bill


----------



## argleargle (Aug 20, 2013)

OT comments removed. This thread is about "dedoming".---Bill

thanks.


----------



## degarb (Aug 22, 2013)

I am being lazy here. But it occurred to me that de-doming my xt-e might be the medicine this led needs-- to fix the color and lux it up. The weird yellow surrounded by purple color is starting to get to me.


I haven't looked to see the best method or if it can be done with a white xt-e. I think I read acetone and q-tip-but at the time of reading, not too interested in doing it myself.


----------



## SemiMan (Aug 23, 2013)

Xte was never meant to be a flashlight led. The phosphor coating process is low cost not perfectly consistent. Not great behind an optic unless you have lots to smooth things out. 

Sent from my Nexus 4 using Tapatalk 4


----------



## degarb (Aug 23, 2013)

SemiMan said:


> Xte was never meant to be a flashlight led. The phosphor coating process is low cost not perfectly consistent. Not great behind an optic unless you have lots to smooth things out.
> 
> Sent from my Nexus 4 using Tapatalk 4



Correct, so, I am wondering what dedoming the xte would do, to solve the above mentioned color issue. And maybe a link to video of someone doing it the easy way, already mounted on board. 

Throw, I don't see to be bad: (4500 typical hotspot with 5300 peak candela in places at .370 amps R5, with a pill sized dropin)

I know that cree says xt-e white is for flood. I read they are about a buck each, so theoretically could solve problems where the xml cannot. And if I remove the reflector, the color is just white. I bought the drop in cause it was cheap, efficient as an xpg. So for $8, I could sate my curiousity and fix a broken 3AA. I was surprised at how good the drop in was, after all the bashing. It is not as pretty as my xp-g's. The color is not 2013 quality, though not as bad as a shongzeng or other chinese led I have picked up at home depot or big lots.


----------



## psychbeat (Aug 23, 2013)

^^^^Just pop that sucker off 
I think Vinh had a thread on dedoming tips or u could pm him for advice. 

The tint will probably shift a bit warmer & more yellow when dedomed. 
It will most likely be more uniform too in the reflector. 

Post yer results too!


----------



## degarb (Aug 25, 2013)

psychbeat said:


> ^^^^Just pop that sucker off
> I think Vinh had a thread on dedoming tips or u could pm him for advice.
> 
> The tint will probably shift a bit warmer & more yellow when dedomed.
> ...



Got around to gooling this on the xte. One person thought it would become royal blue; the other person who claimed to have tried, said it made color separation worse. Both do seem logical thinking back to reading-when the xte first came out- that the phosphors were on dome.

Does make me wonder, why not just put the phosphors on the lens?


----------



## bshanahan14rulz (Aug 26, 2013)

That's a good question, degarb. 

Slightly off-topic, your avatar reminds me of the Philips "alien head" bulbs: http://i.minus.com/ibbnl5spexELL3.jpg ;-)

Lots of phosphors' performance seem to degrade in the presence of heat. Moving them away from the LED, even if just by a little bit, probably has a positive impact on increasing overall efficacy at higher drive currents.XT-E is one way without making a radical change to how you want to use the LED.


----------



## SemiMan (Aug 26, 2013)

It makes the phosphor last longer but you are adding another optical interface which impacts efficiency.

Sent from my Nexus 4 using Tapatalk 4


----------



## Slewflash (Aug 27, 2013)

ILIKEFLASHLIGHTS said:


> There is no substantial proof that a domed emitter will last any longer than a de-domed one. And throw is about doubled on most emitters when the dome is removed. The dome is basically there to protect the emitter and keep it from getting wet or moisture in it.



You're correct about there being no proof that a stock emitter will outlast a dedomed emitter. As long as the inside of the reflector is clean it_ should_ last the same amount of time if driven at the same level. When an emitter is dedomed, the phosphor and bond wires are exposed and they will scratch off/break VERY easily. If there's nothing rattling around in the reflector then this won't be a problem.

Dedoming decreases apparent die size which increases surface brightness. It will suffer a small loss in lumens and a very noticeable tint shift towards the warmer side (but not necessarily increasing CRI).
Depending on the reflector dedoming can increase throw by 2x or more if done cleanly, and usually will at least make it throw 50% further.

IIRC, the dome is there not to protect the emitter (although it does prevent breakage of bond wires and scratching of the phosphor), but to shape the beam pattern. Beam pattern is so important in lighting.

As for why people dedome lights, it's just to increase throw. There's no other reason. It makes the hotspot smaller and more intense. Other than doubling your throw in most cases dedoming has no other beneficial effects. It will suffer a tint shift (some may like this, but it doesn't necessarily increase CRI) and will decrease the total lumens (5%-10% from measurements).

That being said, why would you care about longevity of an LED light? LEDs (XML2) have an _unlimited life time_ "In testing, Cree has found XLamp XM-L2 LEDs to have unlimited floor life in conditions ≤30 ºC/85% relative humidity (RH). Moisture testing included a 168-hour soak at 85 ºC/85% RH followed by 3 reflow cycles, with visual and electrical inspections at each stage" (Taken from XML2 datasheet).
If on the incredibly rare chance a dedomed LED died, it would be a 10 minute job replacing it with another LED. I myself have two dedomed lights, one has been dedomed about a year ago, the other about 2 months ago. Both work perfectly fine.


----------



## jorn (Aug 27, 2013)

Tested my demomed xp-e in a sipik68. Pumped the head full of water. The led die was directly exposed to water for a half hour, when on. Was using the zoom to pump water with while dunked. Not a single flicker. (The driver and battery compatment is fully water sealed. Led die is exposed)


----------



## psychbeat (Aug 27, 2013)

jorn said:


> Tested my demomed xp-e in a sipik68. Pumped the head full of water. The led die was directly exposed to water for a half hour, when on. Was using the zoom to pump water with while dunked. Not a single flicker. (The driver and battery compatment is fully water sealed. Led die is exposed)



Good to know - thanks!!


----------



## LEDealer (Aug 27, 2013)

Slewflash said:


> It will suffer a small loss in lumens and a very noticeable tint shift towards the warmer side (but not necessarily increasing CRI).



10-15% depending on the product. If you are using a more recent XTE (R2), it will be closer to 10% because the dome is not optimized for the new (bigger) die size.

I definitely agree that the color shift will definitely be noticeable.


----------



## RoGuE_StreaK (Aug 27, 2013)

jorn said:


> Tested my demomed xp-e in a sipik68


Slightly OT, but all(?) info on dedoming states the effect on only throw; what's the effect on the _flood_ mode of a zoomie like the sipik68? Less flood and dimmer, or unnoticeable difference?


----------



## jorn (Aug 28, 2013)

I cant see the ~10% lumen loss with my eyes. Flood mode spreads the lumens, so makes it even harder to tell any difference. Focused for throw, the extra lux or cd is easy to spot.


----------



## degarb (Aug 28, 2013)

I may try dedoming with t6 dropin that I just got. I from my previous youtube search, the man dedoming was using a 2.5 amp power source and a specialized temp gauge for a way of softening the dome before removing.

He was using a standard razor to cut. But, I suspect a craft store Exacto (brand named is better) knife would be better, perhaps obviating the need (for specialized equipment) to heat up the led first. ??


----------



## degarb (Sep 3, 2013)

I just dedomed my first xm-l t6. The result was a purple center, no warming, and about half the throw, with reduced output. But the hotspot is smaller.


----------



## SemiMan (Sep 3, 2013)

Sounds like you lost some phosphor. Can you see the phosphor on the removed dome?


----------



## TEEJ (Sep 3, 2013)

Yeah, that's what it sounds like. If you get JUST the dome, its not purple...its warmer. If you accidentally get rid of some phosphor, it gets colder/purple, etc.

Your eye doesn't preceive the purple light wavelengths as well, so even if the output is the same in power, you'll see less with it. The phosphor is there to change the emitted light to more advantageous wavelengths.


----------



## degarb (Sep 7, 2013)

TEEJ said:


> Yeah, that's what it sounds like. If you get JUST the dome, its not purple...its warmer. If you accidentally get rid of some phosphor, it gets colder/purple, etc.
> 
> Your eye doesn't preceive the purple light wavelengths as well, so even if the output is the same in power, you'll see less with it. The phosphor is there to change the emitted light to more advantageous wavelengths.




I just went out and bought best exacto knife. I turned led sideways, used headlamp to see, and lopped off 1/4 (tip) of dome. It sliced through like butter. However, I could immediately see the shift cooler and reduced output. I sliced more of the dome off and it got worse, or subjectively, the same. So, I just tossed the dropin into bag of outdated lights. No headlamp building project for me this month. The replacements is on slow boat from China.

I am thinking the best led and driver (throw/output/runtime balance) really would be an xpg2 with the kaidomain driver http://www.kaidomain.com/product/details.S020075 I think my dedoming days are over!


----------



## jorn (Sep 8, 2013)

Try to just rip the dome off with your finger nail. (If there still is something to grab). 
Remove all of the dome, cutting only the tip off just wont cut it  I first tried to cut some domes. But ended up just ripping the whole thing off, and dunked them in lighter fluid. Most ended up nice. 
I got a neutral xp-g2 on copper pcb driven at 3,04A in a smooth reflector. Really throwy drop in, but beaten by a dedomed xp-e in a smaller sipik68.


----------



## RoGuE_StreaK (Sep 8, 2013)

Just did my first de-dome (XM-L), with 100% success; scored the dome a few times with a blade, then soaked in petrol (91 RON "standard unleaded") for 21hrs. Was waiting to see if the dome just floated off, but it didn't. The slightest of touches with a plastic toothpick and it popped right off, no goo left except a tiny bit under the bond wires. Little bath in some isopropyl (very hard to find in Aus due to drug-lab restrictions etc., used Isocol from the chemist) and she's all good. Surprisingly when I picked up the dome it completely disintegrated into dust.
Seems warmer, and definitely a smaller, more intense die image when behind a lens; seems about 3/4 off it's previous size.


----------



## Jakeyb (Oct 1, 2013)

I just de-domed the XML in my defiant 3c from Home Depot. Mine is the ultimate thrower version with the deep reflector. The results were warmer light and a very tight hotspot. Much tighter than before. I'm very pleased with this.


----------



## SimulatedZero (Oct 30, 2014)

Being that tomorrow is halloween, I feel it appropriate to dig this thread back up from the grave. 

Let's say, given the same reflector, I were to replace a domed XP-G2 with a dedomed XP-L. How much throw would I loose from the larger surface area and would the increase in lumen output be enough to compensate?


----------

