Hi , if I put Silver tape (air conditioning tape) inside the tube that carries the lens
can I reduce the loss of light when I zoom the torch all the way ?
Thanks
one would think…
anything white or silver that can be added would help…
metal tape - want to be sure it doesn;t short something out though…
what this will probably do is increase light in the spill zone, not the ‘hot zone’
it may also make ugly patterns but who cares
wle
I think that will cause artifacts around the projection of the die. A lot of people back out the surrounding area around the LED to reduce artifacts.
A precollimator lens is a good way to collect more light into the beam. With proper lens selection and placement, the beam size (in spot mode) is 2-3 times the area and within 10% of the original beam lux. The light collection efficiency in aspheric lens lights (in spot mode) is typically very bad, around 25%. A precollimator lens can increase the light collection by 2-3 times.
Here are a couple lights I’ve made with precollimator lenses:
This is the precollimator lens I used for my C8 fresnel lens conversion:
http://www.kaidomain.com/p/S020945.18mm-Optical-Glass-LED-Lamp-Lens-1pc
Depending on the size of your light, you might need a smaller diameter lens.
That will increase the light collection but it will be scattered light which will turn into rings or spill after passing through the lens, not increase the brightness of the spot.
Same brightness but a bigger spot typically.
It’s a little unclear what your comments are referring to. I think Enderman’s comment about the light not contributing to the spot is referring to the OP just putting reflective tape around the LED. And Jerommel’s comment accurately describes when a precollimator lens is used.
Honestly I’ve never thought the light loss was much of an issue. When compared to a reflector light they are in a way more efficient. Comparing two reflector lights with the same LED, same drive level and same throw (the zoomie would be smaller in this case) how much light ends up at your target? How much is active at that given throw number. Say the zoomie is only 80% efficient, all of that light is in a beam that reaches your target. In the comparable reflector light a much smaller percentage ends up in the hotspot, remember most of the LEDs output comes out the middle so most of that never hits the reflector and is spill. Yes the reflector light puts out more lumens but most of those are used on spill and not the hotspot. This of course is in a long range use. At close range, when zoomed out, the zoomie looses less light (but still more than the reflector) and by spreading it out in a more even beam pattern again utilizes those lumens more efficiently. The reflector light’s lumens that are used for the hotspot are now used to produce a small area that is either too bright and is distracting while the spill is at a high enough intensity or when the hotspot is a good level of intensity the spill is too dim. Not that there aren’t tradeoffs like the time needed to switch but it seems people get hung up on the efficiency loss in zoomies.
To answer the question and not rant on, I agree with the above comments, the best way to get more output is just with more LED power. Pre-collimators and recycler rings work but are not exactly easy to implement.
OP is talking about a typical cheap zoomie with a lens, not a TIR.
It is far less than 80%…
Source: Automatic beam profile tool | Candle Power Flashlight Forum
Perhaps 80% was a bit optimistic to make a point, I guess my experience is more based on lights with dedomed emitters and higher quality optics. To put some numbers in I compared an XP-L’s spatial distribution curve against the “acceptance” angle of a C8 reflector and a Z1 lens. Being 28.9 and 37.2 respectively. The C8 gets all the area under the curve after 28.9 degrees and the Z1 gets all the area before 37.2 degrees. Of course I’m just counting squares here so not exactly precision science but they are 7.5 and 10 respectively. So the Z1 lens is able to put more lumens (which are cd*sr after all, the chart being cd percentage and angle) into it’s beam than the C8 into it’s hotspot. This thread may be getting a bit more complicated than the OP intended….
I imagine it would be the opposite effect of paint/blackening everything inside the bezel. So blackening all the surfaces reduces beam artifacts and rings, conversely making them shiny would do the opposite. So yes in theory it should produce/reflect more light out of the front.
The best option is to use a light with a bigger AR coated glass lens
We can talk science all day long …Simple answer is you blacken anything and everything because even the reflection off the blob of solder attaching a lead onto the star will show up in your beam .
if you’re looking to reduce losses look at other options ,different emitter ,different driver ,spring bypass,de-doming etc …these lights are what they are and different options will give or take something .
This is an incorrect conclusion. The emission pattern on the XPL datasheet tells you the intensity at different angles, but it doesn’t tell you the total amount of light at different angles. To get the total amount of light you have to integrate around the axis perpendicular to the LED surface. The resulting pattern looks like the picture in this post:
A bit more explanation here:
The thread I posted above in post #4 also has some discussion of the light collection efficiency of a lens light and how a precollimator lens can improve it.
It turns out the C8 reflector collects ~75% of the light into the beam. Aspheric lens lights tend to have much worse efficiency ~25%. This is supported by measurements that djozz did.
Yeah, I always guesstimated “about a third or less” when zoomed vs as a mule. I was pretty close. 
Adding silver tape inside the sliding bezel won’t help.
- Any light reflected from the tape will be scattered. It won’t be focused in the hotspot so won’t add to throw. Instead it may be visible as a slight corona or rings outside the hotspot.
- Adding tape to the inside of the bezel is difficult since that portion of the bezel usually slides directly across an o-ring on the side of the pill. Tolerances are tight at that point. Add tape and the bezel will probably no longer slide. File down the bezel slightly to make room for the tape and the o-ring won’t stay in position, or will rub off the tape as it moves back and forth.
- If you really want to try a silver interior bezel, don’t bother with tape. Instead, remove the entire bezel and immerse it in Greased Lightning to remove the anodizing. Then polish up the bare aluminum.
- I once tried inserting reflective tape on the inside of the bezel. This was tape that had miniature reflectors in it like a bicycle reflector and was designed to reflect incoming light back to its source. My thought was that maybe it would reflect enough light back to the emitter to increase the emitter’s intensity in the same way a Wavien collar works. However, in my testing the tape did not increase lux so I discarded the ideal.
- Best way to reduce lumen loss inside the bezel is probably to use a light with a wider lens, or install an LED Lenser style optic.
- In a cheapie aspheric you can reduce lumen loss in flood mode. I have tried both of the following options and both work well:
(a) Many lights do not allow the lens to retract far enough. Ideally, the back of the lens should be within 1 mm of the top of the emitter. The closer the lens gets to the emitter, the wider the flood and fewer lumens wasted. I typically do this with a handfile removing parts of the bezel, body or pill to allow the bezel to retract further. This sometimes has the added advantage of making the light more compact.
(b) Alternatively, you can add a small reflector around the LED and below the aspheric lens. Small plastic reflectors from maglights or UKE incan light modules work well. Adding a small reflector like this produces a very wide hotspot in the middle of the flood. This dramatically brightens the flood beam making it far more useful. Throw is unaffected though you will get an ugly ring around the hotspot. This is only a problem in white wall hunting.
Mmm, now that the topic's hot, any of you tried sticking a plano-convex lens over the reflector? That'd guarantee maximum light throughput through the aspheric… 
Beam pattern?
Cheers ^:)
Edited: seems Firelight2 was already preparing my answer even before my post submission. 
Hideous. Aspheric lens from a SK98 fits in place of the front lens of a MiniMag. Tried it. Absolutely hideous beam.
Putting an aspheric lens in front of the reflector doesn’t increase throw. Instead you get a projection of the emitter surrounded by a donut-shaped projection of the surface of the reflector. This can create a hideous beam as every scratch, nick and spec of dust on the reflector becomes part of the beam image. Also since the light from the reflector isn’t in the spot, it does not affect throw. Getting rid of this “donut” is actually why some modders paint the reflector black when modding maglights into aspherics.
That said, putting a small reflector around the emitter on a zoomable can be helpful as it dramatically brightens the floodbeam. Also, since the floodbeam isn’t focused any imperfections aren’t visible.
When I tried it, it was only for a few seconds. The beam was so visually offensive I pretty much immediately undid it, never ever ever to try it again.
It was that bad.