what %-age of light passes thru an aspheric?

does a small amount of light get 'wasted' with internal reflections?

or do the same amount of lumens exit the front of the light with an aspheric as a glass lens?

or,

is good reflector design more effective then an aspheric?

optics?

in a nutshell?

Heres my understanding... Any emitted light that does not directly reach the lens is trapped inside the bezel and lost. The better lenses are bigger diameter to capture more light. Lenses with a tighter focus allows the designer to place the lens closer to the emitter, and capture even more of the emitted light.

saablaster... how did I do?

In general, aspherics are one of the most inefficient optical system for a light. Both TIR and reflectors far surpass aspherics in optical efficiency.

If I recall correct my Tiablo with the aspheric lens lost around 30% of total light compared to the reflector. That's according to ceiling bounce test. A narrower beam gets an advantage in this kind of test so the difference is at least as big or larger than my result will show.

Regards, Patric

kramer5150 said:

Heres my understanding... Any emitted light that does not directly reach the lens is trapped inside the bezel and lost. The better lenses are bigger diameter to capture more light. Lenses with a tighter focus allows the designer to place the lens closer to the emitter, and capture even more of the emitted light.

saablaster... how did I do?

Click to expand...

You started out great. I would not simplify it so much as to say that bigger=better as far a diameter. There is more to it than that. It is the balance between the focal length and diameter that makes for a good lens in any given light. Yes the larger the lens generally the more throw it will have but you also have to consider practical things like the ability to easily carry it around.
Yes a lens with a short(relative to diameter) focal length will allow you to capture more of the emitted light but chromatic aberration and reduced collimization occur as you get the focal length shorter and shorter. Some of this(chromatic aberration) can be helped by using a low dispersion glass but that is an expensive option. If you want tight collimation you have to increase the focal length. It's all a big balancing act and some do it better than others.

For single Aspheric Lens lights I have seen at least 20% and up to 40% loss in real OTF lumens as tested by MRGman. The Deft has 2 lens system, so it is better at sending more light OTF.

Nail_B Cree XR-E R2___,__1D Mag__1-IMR18650__Aspheric,_____168.6______3 sec_______,

Nail_B Cree XR-E R2___,__1D Mag__1-IMR18650__Reflector_____235.0______3 sec_______,


Then the Surefire M6 with 5 R2 emitters with reflector vs. Aspherics

Zep-5R2-SF M6 Host____,__3X_AW17670________5 Aspheric R2's_474.8______3 sec_______,

Zep-5R2-SF M6 Host____,__3X_AW17670________5 Cree R2's____863.6______3 sec_______,


The aspherics tested with the LEDZep M6 drop-in were the black holder aspherics. I later put the crome aspherics and we saw 600ish OTF lumens vs. 478ish with the black aspheric holders.

And that's why I later bought the silver aspherics from him and removed the black ones that were in my light!

Now sitting on 3 black anno'ed aspherics though.

Sgt. LED said:

And that's why I later bought the silver aspherics from him and removed the black ones that were in my light!

Now sitting on 3 black anno'ed aspherics though.

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The black aspherics do clear up the spill and make it more of a tunnel vision, but yeah you get hit with a hefty 100 plus lumen fine:thumbsdow

bigC

interesting imfo all,

i guess i can stop sanding this block of glass now

kramer5150 said:

Heres my understanding... Any emitted light that does not directly reach the lens is trapped inside the bezel and lost.

Click to expand...

I'm pretty sure this is not true. If the light hits the reflector before hitting the aspheric, it is still transmitted through the lens, but it ends up being spill and does not get collimated into the main beam and enhancing the throw/lux of the hotspot.

I want to know about those tests that MRGMan did. I'm guessing it was aspheric only versus reflector only. Why not test an aspheric WITH a reflector? I have two aspheric lights with the reflectors in place and I did not notice a large drop in output - only a reduction in spill for an increase in throw. My aspheric MC-E still has tons of spill because of light hitting the reflector before it gets to the back of the lens.

Inliner said:

I'm pretty sure this is not true. If the light hits the reflector before hitting the aspheric, it is still transmitted through the lens, but it ends up being spill and does not get collimated into the main beam and enhancing the throw/lux of the hotspot.

I want to know about those tests that MRGMan did. I'm guessing it was aspheric only versus reflector only. Why not test an aspheric WITH a reflector? I have two aspheric lights with the reflectors in place and I did not notice a large drop in output - only a reduction in spill for an increase in throw. My aspheric MC-E still has tons of spill because of light hitting the reflector before it gets to the back of the lens.

Click to expand...

Correctomundo, give that man a star. Most of the flashlights that have an after market aspheric dropped in have the reflector removed because they don't both fit. If you put the aspheric in front of the reflector its too far away from the LED die and doesn't focus.

the problem is not that the aspheric loses light (its a transparent solid typically loses 4% per surface unless it has AR coatings of whatever light actually reaches it), the problem is the light that doesn't get directed to the aspheric because there is no reflector to collect it and send it all forward from an LED whose output is not going straight out the front.

Most of the light that is lost is because its not directed to and collected by the aspheric system in the first place. The DEFT gets major points on this one because its a 2 lense system. The first smaller lens very close to the die collects a lot of the light to send to the large aspheric lense rather than losing it but still some gets lost.

In the systems I looked at and measured that simply had an aspheric replacing the reflector all of the light that would have bounced off the reflector into spill got lost so typically there was a 40% loss of light.

This was not light that got lost from the aspheric but never got to the aspheric to go through it in the first place. That is why the best lens systems for a LED flashlight is not an aspheric in the first place but a Total Internal Reflection optic that mounts directly over the die and collects all the light from all angles off the surface and sends it through the optic out the front and only the normal air gap to lens surface reflection % is lost.

Inova and Surefire both have or had TIR optics that worked well in collecting and transmitting lights, neither were designed with an ultra tight beam pattern such as the DEFT, but they could and would be far more efficient.

Those lights that use a reflector of some sort to collect light and send it to the aspheric have brighter spill and not so great of a loss of light but it can't all be collimated into the tight beam as you said.

The only other issues with aspherics are the chromatic aberrations as was already stated. And as was already said to do this right requires big bucks for high quality low dispersion glass and A/R coating on top of that wouldn't hurt but simply add more $$.

I am surprised that no one has ripped the TIR lens out of an old Inova T5 and put it in front of a Cree CR-E R2 to see what that looks like.

Inliner said:

I'm pretty sure this is not true. If the light hits the reflector before hitting the aspheric, it is still transmitted through the lens, but it ends up being spill and does not get collimated into the main beam and enhancing the throw/lux of the hotspot.

I want to know about those tests that MRGMan did. I'm guessing it was aspheric only versus reflector only. Why not test an aspheric WITH a reflector? I have two aspheric lights with the reflectors in place and I did not notice a large drop in output - only a reduction in spill for an increase in throw. My aspheric MC-E still has tons of spill because of light hitting the reflector before it gets to the back of the lens.

Click to expand...

What he said was true. He was assuming(I assume) that it was set up properly without the reflector. Yes you can leave the reflector in but it looks nasty.

MrGman said:

Inova and Surefire both have or had TIR optics that worked well in collecting and transmitting lights, neither were designed with an ultra tight beam pattern such as the DEFT, but they could and would be far more efficient.

Click to expand...

It is true that the TIR optics could be made to throw as far as the DEFT's lens but when is the last time you saw a TIR that size? There are practical limits to TIRs when it comes to size and weight.

saabluster said:

Yes you can leave the reflector in but it looks nasty.

Click to expand...

On a whitewall, yes. But out in the field, I still find the spill quite useful. And if you add a diffuser cap you are just throwing away free lumens by not using the reflector.

Isn't that a rift in the time space continuum, a quantum singularity that if you pass through you wind up either on the other end of the galaxy or in the past by 100 years?

Nope... there's a 110V ac plug in the lower left

from what i've read, the most efficient reflector is Recoil LED

Inliner said:

I still find the spill quite useful.

Click to expand...

For me to poop on.

Inliner said:

And if you add a diffuser cap you are just throwing away free lumens by not using the reflector.

Click to expand...

:thinking: Umm...what?

good question.

I was trying to say that if you also want to use your aspheric as an up close task light with a diffuser, you are going to have significantly less light without the reflector.

But obviously flood light repulses you...