What is not mentioned yet is the influence of the the beam angle on zoomies, the good old XR-E has a 90deg beam angle which makes the sk68 (together with its quite optimal optical lay-out, which can not be said of most other zoomies) so effective. The most popular leds today are Cree's XP-E, XP-G and XM-L (or their mark2), and the beam angles (angle at which the light intensity has dropped to 50 % of the max) are resp. 110deg, 115deg, 120deg. (or something close to that, too lazy to check it now). So the xpe has a bit less light loss in a zoomie than a xml. However there are some leds that have a narrower angle, the narrowest I know is the Osram SSL80, which has a beam angle of 80 degrees (it has a special shaped dome). These leds perform much better in a zoomie. I have a SSL80 sk68 mod that is doing very nicely, the output zoomed out is very close to the output of a reflector light with the same led, and zoomed in gives 72% of the output of zoomed out, no other zoomie comes close to that. The SSL80 is not as efficient as the latest Cree's but that is more than compensated for when used in a zoomie.
Aspherics work best when as much as possible of the raw light coming out of the emitter passes through the lens instead of hitting the bezel. The narrower the beam angle the better. That said, a narrow beam angle on a low-output old LED still might not be able to compete with a highly driven modern LED with a wider angle.
Tint is completely unrelated to the aspheric lens. It’s solely due to the emitter the manufacturer chose to put into the light. If you don’t like the tint you can swap the LED in an aspheric just like you can with a conventional light. I’ve done it many times. The tint of an XML2 neutral or ZPG2 neutral looks the same regardless of whether it’s installed in an aspheric or reflector.
take a zoomie w/ plastic lens that has a purplish beam, put in a glass lens, and see it turn the (still terrible but not purple) tint of the emitter whiter
not all plastic lenses have that terrible effect, but many do
Hm. I suppose some of the cheap plastic lenses might slightly alter the beam. But not by a huge amount.
I’ve generally replaced the emitters in my zoomies with neutral tint XML2 and XPG2 emitters and the tints look exactly the same as when those emitters are installed in high-quality reflector lights. No hint of green or purple anywhere. And the zoomies I do this with continue to use their original cheap plastic lenses.
Zoomies have their own advantages and the most significant one is offering relatively better throw than the reflectored lights. The problems with the zoomies we have are probably due to the budget lights manufacturers refuse to make good quality zoomies for some reasons while high quality reflectored lights are very common.
I do notice the blueish or purplish tint in all of my zoomies, from SK68 clone to Romisen RC-C8 and they were ugly and this is another reason I don’t play around with zoomies anymore. Perhaps a neutral/warm/dedomed LED would looks better.
+1. I’ve owned a lot of zoomies and the tint (especially ’round the edges) has always bothered me.
The quality of glass definitely has an effect on tint, and that’s why the properties of optical glass (used in camera lenses) is so critical - and expensive. I figure cheap plastic lenses are even (much) worse in this respect.
The last zoomie I bought was just a month ago and it has this purple-ish tint that irritates me no end. But I can’t complain, since it is a cheapo one that I ordered to use as a loaner
I'm a bit confused here: It is obvious that a reflector would benefit from de-doming, as more light will be bent by the reflector. But would a zoomie also benefit from de-doming? Or would more light just hit the sides of the host and not be directed through the lens?
Then another question: would de-doming the LED in a LED Lenser light see any increase / decrease?
Dedoming increases the throw and decreases the lumens in ALL led lights. This includes both reflector and aspheric lights. It should also increase the throw in an LED Lenser… but at the cost of worse flood.
Note that dedoming also changes the tint, usually making it a bit warmer.
BanglaBob,
Yeah those bluish tint are irritating. Nevermind I am not going to purchase anymore zoomies until someone has came out a really nice quality one or one with BIG lens.
Lothar,
You may read DrJones very detail explanation here .
It’s a common misunderstanding that the beam angle of a dedomed LED would become wider and more photon hitting onto the reflector resulting more throw, in fact it is not at all because this doesn’t explain why dedoming works with aspherical lens as well. It’s some kind of internal reflection caused by the dedoming that makes the luminance (aka surface brightness) of the die much higher. It has similar effect with the Wavien Collar.
I had my Dereelight XSearcher (aspherical) de-domed last year. What used to be decent thrower is now almost in the monster-class :bigsmile: :bigsmile:
It also got quite a lot warmer, which is great
I might be wrong here but dedoming a LED in a zoom setup is going to wast a lot of light. To my understanding the dome serves as a lens that bends the light and allows it to escape from the led die forward.
If only the directional part is being captured then the rest that hits he bazel is lost. In make perfect sens to dodome in a relfector. More of the light is bend by the reflector in to a beam with less flood.
Apparently there’s more going on here than that. It has been well confirmed that dedoming can give a very significant increase in throw even with aspheric lights. There was a thread last year either on BLF or CPF where the owner of OMG Lumens posted confirming it (his company makes the DEFT flashlights).
Obviously this wouldn’t be the case, if dedoming only increased the intensity of the light going to the sides and not the light forward into the lens.
I think the dome does two things:
(1) By changing the interface on the top of the die, more lumens are emitted instead of being refracted back into the die crystal. The result is overall lumens increase.
(2) It also enlarges the image of the die like a magnifying glass. Because the image is larger, the light is less concentrated… it’s harder to focus and has lower luminance…. so throw decreases.
I am not sure whether dedoming would change the light emitting angle, but I can be certain that dedoming increases throw due to the increased luminance of the die, not because of a less collimated light.
Imagine that you have a aspherical flashlight, say a UF T20. You can try to put a pre-collimation lens in between the aspherical lens and the LED. The result is you will see a larger projected die image BUT without any increment in throw. Yes, the pre-collimated lens will gather and direct more light into the aspherical lens so that they were not wasted inside the bezel, but this will only give you a higher OTF lumens NOT higher candela. It is the luminance which does the job to increase the throw (candela), not lumens to be exact.
Same goes to the LED dome. Again I don’t know if the dome is actually directing more light forward, but anyway the candela won’t be higher with a dome-on LED just because you think it should direct more light forward. The “larger” die image you see is just a perceived die size, I can simply put a 20mm pre-collimation lens in front of it and see an even much “larger” die size but that wouldn’t change the LED luminance and help in improving throw anyway.
Actually, my guess was that magnifying the image of the die with the dome actually decreases luminance, and thus reduces throw, because the lumens aren’t coming from such a concentrated area. I could be wrong though… I’m not a physicist.
Yes I understand what you mean and that is why I bring up the pre-collimation lens as an example. Of course the LED dome is not exactly a pre-collimation lens but the bigger die size you perceived with a domed LED can be related with the pre-collimation lens as well. I am neither expert nor physicist too and I found these out through reading in the forum and some simple experiments done by myself before.
Again you should check out DrJone’s thread in explaining the dedome and light emission behaviour.
This post has an excellent technical explanation about zoom vs reflector. Too bad the images are no longer available. Would any of you happen to still have the images?
