Lenses

[robert.t]

Let me start this thread with some words about LED Lenser. I realise the community is somewhat divided on this topic, but I recently got myself a K2, a K3 and P6.2 to try them out after I was somewhat impressed by someone else's K3 they showed me. Before that, I'd only seen them in the "try me" blister packs and been generally unimpressed with them.

The following is a bit of a digression from my main point, so I'm going to indent it so you can skip over if necessary - read on if you're interested in my impression of these 3 LED Lenser lights.

The P6.2 is not bad, possibly quite useful. I decided of the "full size" Lenser range it was the most practical, being 2xAA, it's not too big and produces enough light to be useful. The optics seem terrible if you actually look at them, with what looks like glue and cracks everywhere, but it works. The result is surprisingly good, despite some nasty chromatic aberration around the edges of the beam, but I've seen much worse from cheap LED lights and it's 100 times better than a Maglite. I've yet to actually try it properly outdoors, but I'm led to believe the throw should be quite impressive in that mode.

The K3 is perhaps the most useful and will be finding its way into my grab-and-go toolkit, basically for inspecting the insides of electronics and suchlike. In flood mode, the nice even beam profile is perfect for this, and because it's so small it's ideal for close up work. The main downside of this light is the batteries: 3 coin cells with a total runtime of about 30 minutes. Ouch.

The K2 is the most worthless piece of garbage it's been my misfortune to come across. The twisty head doesn't work properly, there's a wire sticking out of the tail. There is nothing to redeem this light. The only reason I still have it is that I bought it for so little that sending it back wouldn't have been worth the postage cost.

In the case of the K3 and P6 which are not nearly as awful as the K2, the build quality is certainly nothing to write home about. It's probably somewhere between a really cheap Chinese light with burrs everywhere and a somewhat better Chinese light. I'd perhaps call it competent. The threads seem pretty clean, parts seem to sit flush, etc. It's nowhere near the excellent quality you'd get with Sunwayman, Xeno, etc. The matte coating (I think it's a coating rather than some special anodisement, but I don't really know) is novel and probably aids the grip, but that's cancelled out by the poor knurling and I don't much like the feel of it. The tail clicky is functional, but feels cheap and "bouncy".​

So, if you read the above you'll see I actually kinda like the K3, but what I'd really like is something better made, with a single AAA or AA battery and an aspheric lens fixed in the flood position. That's right, flood, not throw. People seem to go out of their way to get custom aspheric throwers, but I don't see anyone talking about aspheric floodlights. Why not? The completely even beam profile is extremely useful and works very well in a small light. I'd really like one without the nasty chromatic aberration of the LED Lensers, preferably made out of glass, crystal or a very tough scratch-resistant plastic, AR coated, with no zoom and proper impact & water resistance. Does such a thing exist?

If such a thing does not exist, and this might be the wrong forum but I'll ask anyway: can one buy an aspheric lens off the shelf, and what is involved in modding a light to use one? Would it even be possible to do this if like me, you want fixed flood not throw?

 

[AnAppleSnail]

For that lovely even flood, you may want a "Mule" light, with no optic or reflector on the LED. This would give a wide (120 degrees or so) spread of light. This wide beam spreads your lumens out a lot - A 300 lumen pocket rocket would give below 300 lux at 1m distance.

Is that the wide width you want? If not, you may need an aspheric and some JB Weld to lock it down. Once a light-maker is faced with making the perfect width of flood, most throw up their hands and give enough range of motion to give wide flood and extreme focused throw, giving a more flexible light for about the same money (And eliminating expensive and shelf-filling guesswork).

 

[ven]

Caddylover has modded his d40avn and has a link for aspheric lenses to buy

I have a few lensers,hardest bit is making sure its genuine!
Once thats established the ones i have/use have been good.Latest and last for a while is the t7.2,great light and runs on 4xAAA cells,obv not regulated like the M series but will last many hours of usable light......

I have found on the cheaper/smaller lights the mark/scuff easy,but then again so have other key chain lights....

Agree though,not the best ano.........

 

[Fireclaw18]

The bad news:
* It's not that easy to mod a fixed-focus light into a zoom light. In order to make an aspheric zoom light work, the bezel needs to slide back and forth. The full extension needs to be precise. When the bezel is extended it needs to stop with the LED die right on the focal point. Even half a mm off and the image of the die will be blurry and you'll get less throw. In flood mode, the back of the lens should get as close as possible to the top of the emitter. The closer it gets, the wider the flood.

* LED Lensers use a uniquely engineered optic. It's a combination of TIR and aspheric lens, with a pocket for the LED to sit in. The LED is mounted on a pillar instead of a traditional star and stays in this pocket in both flood and spot mode. The result is regardless of bezel position, all the light goes into the optic so you get roughly the same lumen output in both modes.

* With a typical aspheric lens, the back of the lens is flat and the emitter sits on a traditional star. In flood mode, this might catch all the light so you get high ouput. But in spot mode, much of the light emitted sideways from the emitter will hit the sides of the metal bezel instead of going through the lens. This can result in a loss of 50-70% of total lumens (but still increases throw). To reduce this problem, use a wider lens with short focal length.

* In order to get maximum throw, zoom lights should use an emitter with maximum possible luminance (think of this as lumens per square mm of LED die). The emitters with the highest luminance tend to be ones with small dies. They're less efficient and produce less lumens than larger emitters. An XRE may outthrow an XML, but the XML will have a much brighter flood mode.

The good news:
* There are literally dozens of budget zoom flashlights available. Many are in the $5-$10 range. Some better made ones might be in the $15 to $20 range. Browse through the selection of styles, read some reviews and then pick one. DealExtreme has an enormous selection. The most popluar one is probably the AA sized Sipik 68.

* It is possible to buy aspheric lenses by themselves. I recently bought a bag of 10 from CN Quality Goods for just a few $.

* Most stock budget zoom lights leave a lot to be desired. If they have an XPE or XRE emitter, throw might be good. Possibly better than an LED Lenser, but flood is usually a lot worse. The flood also often isn't very wide.

* It's possible to mod a budget zoom light for a dramatic increase in performance. A well done mod can increase the width of the floodbeam to over twice stock... MUCH wider than the flood on an LED Lenser. And if heavily driven it can easily outthrow an LED Lenser as well.

* Suggested mods: Replace stock emitter with dedomed emitter (dedomed XPG2 works well. For brighter flood, try a dedomed XML2). Dedoming the emitter reduces overall lumens by approximately 20%, but increases the throw by 70-100%. It also makes the color temp approximately 1500 degrees warmer, so start with a cool white LED for best results. Replace the driver with a stronger one. 3 amp drivers work well for li-ion powered lights. After installing the new LED, you may need to fine-tune the focus. This can be done by adding thin aluminum strips around the top of the pill, and with a hand file. If you're not comfortable dedoming your own emitters, Mountain Electronics sells dedomed ones.

Example: My current EDC light that I've been working on is a modified budget zoom light (Aleto N8 purchased on Ebay). In its modded form its much brighter than any similar sized LED Lenser, even with the less efficient lens system. It has the following features:
1. Small size and cylindrical shape good for pocket carry: 97mm long x 24 mm wide.
2. Replaced tailcap switch with electronic sideswitch.
3. Replaced driver with 105c with FET mod... approximately 6 amps to the emitter on a fresh INR cell.
4. Runs on 1x 18650 cell. This light is smaller than an LED Lenser than runs on one AA cell, but holds a much larger and more powerful battery.
5. Emitter is a dedomed XML2 on direct copper. Total output in flood mode is probably 1000 lumens, though I don't have a lightmeter so can't tell for sure.
6. I modded the focus so the lens retracts to within 2 mm of the top of the LED. This results in a flood mode that's nearly 90 degrees wide.... much wider than an LED Lenser or any stock budget light's flood mode. Wider than the spillbeam on any of my reflector lights.
7. With the dedomed emitter the light still has excellent throw for its size. Despite losing over 50% of the lumens into the side of the bezel in flood it still easily out-throws any of my other unmodded lights including my LED Lenser P5.
8. Nicer UI - with the mods I was able to add my driver of choice: DrJones lumodrv. Gives me shortcuts to min, max, 25%, plus 2-way ramping with 34 steps. Also has hidden momentary mode, low voltage stepdown and cutoff, battery voltage checker, and strobe.

 

[Fireclaw18]

For that lovely even flood, you may want a "Mule" light, with no optic or reflector on the LED. This would give a wide (120 degrees or so) spread of light. This wide beam spreads your lumens out a lot - A 300 lumen pocket rocket would give below 300 lux at 1m distance.

Is that the wide width you want? If not, you may need an aspheric and some JB Weld to lock it down. Once a light-maker is faced with making the perfect width of flood, most throw up their hands and give enough range of motion to give wide flood and extreme focused throw, giving a more flexible light for about the same money (And eliminating expensive and shelf-filling guesswork).

I found that with good modding an aspheric zoomie can get a beam around 90 degrees wide. That's wider than a typical reflector light's spill. Not far off from a pure mule.... and unlike the mule, the zoomie can still focus to a point for throw. The trick is to adjust the focus so that the back of the lens retracts almost within touching distance of the top of the LED. For best results use a dedomed LED... without the dome in the way there's room to allow the bezel to retract even further.

 

[robert.t]

For that lovely even flood, you may want a "Mule" light, with no optic or reflector on the LED. This would give a wide (120 degrees or so) spread of light. This wide beam spreads your lumens out a lot - A 300 lumen pocket rocket would give below 300 lux at 1m distance.

It's not quite the same effect. I have a DGQ Spy, which is a mule and the beam profile is very different. As you say it puts out a fairly even spread of light. However there are two issues:

1. There is still a hotspot. Less noticeable, but definitely not the nice even flat disc of light you get from a Lenser in flood mode.
2. The angle is too wide, so this is potentially bad if you don't want to get blinded by the spill or reflections, i.e., for close inspection inside a metal case or similar.
3. Related to these, the light isn't concentrated within the defined disc, so you are essentially wasting lumens on unwanted diffuse lighting all around rather than putting the light exactly where you want it.

The term "flood" is a bit odd in a way because actually the desired effect is that of a spotlight. A very well defined spotlight, with an even cone of light, not a hemisphere emanating from a point source (which is what a mule is). I would have called it a spot except for the fact that it's termed flood mode. It's confusing either way because the terminology is somewhat misleading.

 

[robert.t]

It's not that easy to mod a fixed-focus light into a zoom light.

To reiterate a couple of my original points:

• I don't care about zoom. No need to mod anything to have zoom, it's all about fixed focus. I'd rather have something that won't move about and is properly waterproof.
• There's been much discussion of throw before. I'm mostly interested in flood, or what might be more accurately referred to as spotlighting, except that I mean what in LED Lenser is flood.

With a typical aspheric lens, the back of the lens is flat and the emitter sits on a traditional star. In flood mode, this might catch all the light so you get high ouput. But in spot mode, much of the light emitted sideways from the emitter will hit the sides of the metal bezel instead of going through the lens.

That sounds like it wouldn't be a problem if I wanted to make a fixed focus [flood] spotlight, and could probably get away with a fairly small head, no? It sounds like the large heads associated with aspheric throwers are because of the problem you describe, which doesn't apply when focusing for an even flood/spot (see my last post for points about why flood/spot are confusing terms here).

...the AA sized Sipik 68.

I found out about those a few weeks ago and mine is currently in the post from China, should get here in a week or so, fingers crossed. Looks like fun for such a cheap light. Once it arrives I'll take it out one night and compare it to the P6.2.

LED Lensers use a uniquely engineered optic. It's a combination of TIR and aspheric lens, with a pocket for the LED to sit in. The LED is mounted on a pillar instead of a traditional star and stays in this pocket in both flood and spot mode. The result is regardless of bezel position, all the light goes into the optic so you get roughly the same lumen output in both modes.

It is possible to buy aspheric lenses by themselves. I recently bought a bag of 10 from CN Quality Goods for just a few $.

Very interesting and useful information, thanks.

 

[Yamabushi]

A very well defined spotlight, with an even cone of light ...

For that effect, try a diffuser on a flashlight that is otherwise a thrower.

 

[robert.t]

For that effect, try a diffuser on a flashlight that is otherwise a thrower.

I have a diffuser for my Nitecore P12 and the effect is pretty much identical to a mule. Great for lighting up a room, but completely different to the defined spot that I'm looking for.

 

[TEEJ]

Vinh's version of a zoomie aspheric gives super even lighting in the flood position.

He has various LED choices for it, and I have, amoung others, an MTG2 zoomie of his that's really useful. The XML2 version kicks *** too for more range.