The L21B attains the output/throw parameters claimed by Wurkkos, so comparing against L21B is like comparing against Wurkkos’s own claim, which I’m sure you would agree is an important comparison for anyone buying the light.
For sustainability/efficiency, if there’s a better option that costs less, I don’t see a reason to not bring it up. I say that being 40% more efficient is a pretty major improvement. If you can name a light in the L21B’s power/price class that out-performs it in all departments from throw to efficiency, by all means do so–people looking for a rec would find that helpful.
I guess L21B is a good choice for those who absolutely needs that higher efficiency at 30% and much higher output at turbo. While I love Convoy lights and have quite a few of them myself, I never even considered L21B. Too bulky for my taste, no side button for such a big light is a deal breaker for me. And I wanted thrower with minimum spill, which is not the case with L21B. I find Wurkkos TD01C to be an excellent thrower for what it cost.
IMO 40% efficiency deficit is significant. It essentially turns a 5000mAh 21700 battery into 3000mAh 18650 battery. With a 40% more efficient driver you could make the light a lot smaller / lighter while keeping the same output. Convoy’s UI is not the best but their driver efficiency is top notch, from many real world tests. I’d be pissed if my buck driver performs worse than linear driver.
Must be valued argument for some, but I don’t buy flashlights for lab tests and only absolute the most efficient ones. I have many that are more efficient than others as well as less efficient ones. Yet I absolutely enjoy using them all.
Depends on your needs. If I took my OG D4s backpacking I’d likely be disappointed by their relatively inefficient driver (and attendant additional cells to compensate). But instead I use them around the house for shorter-duration tasks: projects, walking the dog around the block, etc - and they still last weeks.
This may be an oversimplification, but it seems to me that the TIR optics can do everything that the reflector can do and then some. What’s the advantage of a reflector?
The only disadvantage is light loss of the TIR which is not the case for reflector. But I absolutely love TIRs and buy flashlights with TIR if such option is available
Perhaps weight and cost in larger lights? I like the ease of changing the optic in my convoy M21H to the beamshape I desire, I can’t see how a TIR would work for something the size of a BLF GT though…
Can they, though? TIRs have gaussian beam profiles of varying FWHMs, with more or less additional scattering added on the surface (beaded/frosted/smooth).
Reflectors have a hotspot that has a hard cutoff, then a spill of more or less constant brightness, and another hard cutoff.
It really depends on application and preference.
If you want to see far, while also seeing where you’re going, reflectors are king. Bright hotspot to aim at points of interest, and a lower constant brightness spill to illuminate your surroundings.
If you want to light something up with a pleasant beam (work light, indoors flashlight, hiking light where you are not interested in looking far), TIR beam profiles are usually more pleasant as there is no hard cut-offs and no super bright spot to blind you.
Reflector weight and losses also scales better with larger lights. TIRs get heavier by volume, reflectors only by surface (and a bit more because they need to be thicker). TIRs also have more losses the larger they get, while reflectors don’t.
Ok, but say I’m not even interested in the technicalities of light collimation in flashlights (I am) - practically, what beam would be most useful and satisfactory? Sky is the limit. Kind of @Lightbringer’s hole vs. drill dilemma.
I would argue that whether for a flodder or a thrower or some special-purpose light (bicycle, headlamp) the TIR lenses stand a better chance to align with the needs as they can produce a sharp far-reaching spot and be as floody as needed (to a point that I can even see my feet :-). And the spill can be tamed so that it doesn’t overwhelm the spot and still be useful.
Is it true though that reflectors+flat lens are more efficient than well-designed TIR? I thought that, all considered, they were comparable?
My pet peeve with reflectors is not so much the spill overwhelming the spot as @Lightbringer pointed out (try shining a thrower with a reflector through a window for instance), but the sharp cutoff between the edge of spill and the darkness (and this edge can be quite a bit in front of me, not far from the middle of my field of vision).
Don’t quite know how to explain it but I find it distracting when trying to recognize shapes in front of me illuminated by the spot. When I move the light in search of something or to get a better picture of what’s in front of me, this spill edge produces false shapes that interfere with the shapes I’m trying to recognize.
This is a case of “speak for yourself” I’m afraid. What’s wrong with “useful spill”? Whether a spill is useful depends on each person’s use case. When I use flashlight as a walk/safety light, both near and far illumination is useful, near for your steps, and far for safety. A light like IF22a with pencil beam and very little spill is an example of a “not useful spill.”
A faint spill “completely washes out immediate foreground… to the point what you are shining on looks like it’s in the dark”? A faint spill washing out hotspot? Needs elaboration as it seems to me it is the opposite that’s true: pupils constricting in response to bright hotspot and reduces visualization of faint spill.
That’s probably because this is something we don’t experience IMHO. There ARE certain situations where a spot with limited spill is useful (eg hunting ), but even then it is not a case of a faint spill “overwhelming” spot to the point that “what you are shining on still looks like it’s in the dark.”
If you had complete control of the beam shape and distribution, how would you design it (and would you design it to resemble what reflectors normally produce)?
Depends on the size. The larger a TIR the more losses it has. A reflector stays the same. This (next to weight) is the reason why pretty much all large throwers have reflectors.
If all you’re doing is shining the hotspot fairly close to you, ie, for walking, where the spill lights up what’s immediately in front of you, and the hotspot lights up the path maybe 20’-50’ ahead, then that’s fine.
But if you’re using the light to look at something in a forest, tunnel, dark tree-lined path, etc., forget it. You’ll be lighting up the trees right in front of you or the sides of the tunnel, and what’s way down yonder will be in the dark.
Ever see things like flash pictures taken at a wedding venue, etc., where the people are well-lit, but the background is dark if not completely black? That’s the effect I’m referring to. Reviews of throwers have plenty of beamshots of exactly that. “Something moving between those trees? Let’s have a look!” So you light it up, see brightly lit trees all around, but what’s in that hole stays in the dark.
I just grabbed a random pic of a tunnel (so much for goggling “flashlight illuminate tree lined path”…) that shows this.
So you can have a machete-wielding psycho killer rushing at you from the other end of the tunnel (maybe that teeny spot in the middle?) but all you can see is the walls of the tunnel, thanks to the “useful spill”.
Try that with a LEP or something, and you’ll see the machete-wielding psycho killer just fine.
Hell, I could probably see what’s down that hole better with my Cat Mini and its whopping 500 lemons than that big honkin’ light used in the tunnel pic.
Exactly - I’m glad now you understand how a spill is useful in a walk light. That’s why I had that gentle reminder: “speak for yourself.”
Just a “random” picture of a guy in a SMALL TUNNEL to emphasize brightness, with some “random” flashlight that might just be the brightest flooder one could find. Thanks for the good laugh that’s actually pretty funny. I hope you’re not serious.
If I may show beamshot of my TS30S thrower and not some weird tunnel shot, showing spill barely visible, not washing out foreground “to the point that what you’re shining on still looks like it’s in the dark (!?).” Spill washing out hotspot is unlikely because a hotspot is just that, the brightest point. Unless when I am taking evening walk in a sewage tunnel. Kidding aside, could we move on from this please.
What’s wrong with “useful spill”? Whether a spill is useful depends on 
