# Olight M21 (Luminus SST-50) Review: RUNTIMES, BEAMSHOTS and more!



## selfbuilt (Jan 8, 2010)

*Warning: pic heavy, as usual. *

*Manufacturer's specifications, condensed from Battery Junction’s website:*

Luminus SST-50 LED
Powered by: 2 x CR123A / 2 x RCR123A / 2 x 16340 / 1x 18650 / 1 x 17670 batteries 
Dimension: Length: 145.5mm (5.7”), Bezel Diameter: 40.2mm (1.6”), Body Diameter: 24.80mm (0.98”), Weight: 119g(4.2oz), Color: Black 
Tactical momentary-on forward switch, protruding switch for easy momentary or click to lock on
Three digitally controlled constant brightness levels and strobe. 20lm (30hrs)-80lm (8hrs)-500 lm (1.2hrs), Strobe(500lm/2.4h).
Auto memorization of specific function for instant access
Front removable stainless steel striking bezel and rear striking bezel, removed for daily use, installed for close quarter combat
Ergonomic design with solid structure for easy operation, anti-slip body texture that give you a firm tight grip
Full orange peel reflector for wide flawless beam
Strong / quick to release lanyard to prevent loss and easy access
IP68 Water resistant
Anti-shattering ultra clear lens, anti-scratching and anti-slip
Metal ‘cigar hold’ ring optimally positioned offer additional anti-roll properties and is pre-installed but removable for smoother body hold
Stainless steel pocket clip
Operation: For momentary light, gently press (no click) the tailcap push-button switch. For constant light, fully press (click) the tailcap pushbutton switch.
To switch functions, click on the light, loosen the head by 1/8 of a circle and then tighten it down, the light will move to the next function. Repeat the same operation for further functions.
MSRP $120
The M21 is the “sequel” to the highly popular Olight M20, reviewed over a year ago. How does it compare? Read on to find out … 















The M21 comes in a presentation-style plastic carrying case, similar to the M30. The light and all accessories are carefully packaged in cutout foam. Included with the light is a sturdy belt holder, spare O-rings, GITD tailcap button cover, good quality wrist strap, 2xCR123A battery carrier, tactical grip ring replacement cover, and manual.
















From left to right: Duracell CR123A, AW Protected 18650, D-mini VX Ultra with D65 extender, Olight M21, Olight M20, JetBeam Jet-IIIM, ThruNite Catapult (no extender)

*Olight M21*: Weight 119.5g, Length 145.2mm x Width 38.5mm (bezel)
*Olight M20:* Weight: 120.0g, Length 144.0mm x Width: 35.7mm (bezel)

Overall size and weight of the M21 is similar to the older M20, although the head is just a bit wider and longer on the M21. But unless you are comparing the two side-by-side, for all intents and purposes the hand feel is very much the same. This is a high quality light that is comfortable to hold and use.






Like the M20, all components seem sturdy and well built. Everything fits together well, with double o-rings and smooth screws threads at all openings (tailcap threads are anodized, allowing tailcap lockout). Tailcap spring is not exposed, but encased within an assembly with a button top. Note that the tailcap is interchangeable with my older M20 – nice to see they have kept the specs consistent for over a year! :thumbsup:. 

There is a spring mounted on the positive contact board in the head, so recoil should not be a problem. And newer flat-top higher capacity 18650s should work fine. 

The bore width is good, so all batteries should fit. A battery magazine is supplied to help prevent rattle with 2xCR123A. Note that the magazine is optional, but if nothing else, it provides a good storage means for backup cells.

Machining and anodizing of the light are top-notch on my sample. The raised checkered portions help with grip, though not as "grippy" as aggressive knurling. The attached anodized clip and grip ring also help enhance grip, and both are removable. Included in the kit is a smooth replacement cover for the grip ring (i.e. the grip ring screw threads would be exposed otherwise). Overall, I would have to say hand feel remains excellent in all configurations.






The light can't tailstand - but that's not uncommon for "tactical" lights, since tailstanding rings tend to obstruct easy access to the clicky switch. Light comes with a forward tactical clicky with good tactile feel (momentary on, click for lock-on).






The light features a scalloped stainless steel bezel ring, which could serve as a strike bezel. The Luminus SST-50 is clearly visible well centered in the reflector. :thumbsup: The reflector is fairly heavily textured, which should provide a very smooth beam. Given the larger die of the Luminus LED, I do not expect it to throw as well as the original M20 (i.e. harder to focus to a fine point).

And now for the requisite white wall hunting  … all lights are on Max with OP reflectors on AW 18650, about 0.5 meters from a white wall. 

_*Note:* the tint of the M21/M20 comparison pics is thrown off by the very green M20 - my M21 more closely matches the tint shown in the other light comparisons._








































The M20 has what I consider to be a very standard beam profile for a tactical light - moderate spillbeam, reasonably bright spill, strong hotspot with good throw. The M21 certainly carries on this tradition, with a slightly wider spillbeam and less focused hotspot, consistent with its emitter/reflector combination.

Although hard to see above, the M21 has a fairly premium cool white tint. Early M20s tended to have R2s with the greenish WH cool white tint (which is throwing off my camera in the first set of comparisons). My ThruNite Catapult and Lumapower Dmini VX Ultra (both SST-50-equipped) tend to be just slightly on the purplish-side of premium white. For those of you not familiar with tint bins, please see my Colour tint comparison and the summary LED tint charts found here. 

Here are some close-ups at 5m to better show you the hotspots. Both lights on Max on 18650. The height of each image is ~1.25m.














Pardon the spackle marks (this is from an unfinished part of my basement :laughing. But as you can see, the M21's hotspot illuminates an area about twice as wide as the M20 at 5m. The width of the hotspot is about 1m wide for the M21, half-a-meter for the M20, at this distance.

*User Interface*

UI is identical to the M20, and very straight-forward - press the forward clicky for momentary on, click for lock-on. 

Light moves between modes by a simple switch of the head - loose/tighten the bezel to move to the next state. Sequence is: Lo - Med - Hi - Strobe, repeated in an endless loop. Light features mode memory, and retains the last setting used (so you can always have it come on where you want).

There is no sign of pulse width modulation (PWM) on any output mode - I believe that the light is current controlled. 






Strobe is a fairly tactical (and certainly annoying) 9.5 Hz. :green:

*Testing Method:* All my output numbers are relative for my home-made light box setup, a la Quickbeam's flashlightreviews.com method. You can directly compare all my relative output values from different reviews - i.e. an output value of "10" in one graph is the same as "10" in another. All runtimes are done under a cooling fan, except for the extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

Throw values are the square-root of lux measurements taken at 1 meter from the lens, using a light meter.

*Throw/Output Summary Chart:*
















As expected, the Max overall output of the M21 is higher than the original M20. The low-level is also slightly higher, but not significantly so. As predicted from the beam shots, center beam throw is indeed reduced on the M21 - but still quite acceptable for a general purpose/tactical light.

Note that my lightbox seems to be underestimating the relative output of the M21 compared to the other lights (the ceiling bounce results suggest the M21 is actually ~40% brighter than the M20 on max).

*Output/Runtime Comparison:*

*Note:* _Effective January 2010, all CR123A runtimes are now performed solely on Titanium Innovations batteries. You can compare the generally excellent performance of these CR123A cells relative to the Duracell/Surefire cells used in all my earlier reviews here. I have marked all the new runtimes of lights with Titanium Innovations CR123As on the graphs with an "*". _






Taken in isolation, the runtimes on all batteries seem reasonable and consistent with what I would expect. Note that like the M20 (and many other multi-power lights), the M21 bypasses the protection circuit cutoff on 18650 batteries. You should stop any run on 18650 once the light begins to dim noticeably, to insure you don't over-discharge your batteries.































The SST-50-equipped M21 is definitely brighter on Max than any of the single-die Cree lights, but the difference is not as high as you might expect (~25% according to my lightbox, ~40% according to ceiling bounce). The Lumapower Dmini VX Ultra and ThruNite Catapult (not shown) are both SST-50-based lights driven harder on Max – but at the expense of runtime and with greater heat generation. The M21 likely strikes a good balance for long-term stability.

Overall, runtimes seem pretty reasonable for the output levels - the M21 doesn't seem quite as efficient on Med as the original M20.

*Potential Issues*

I can’t really think of anything significant.  The M20 has proven itself a reliable and robust light, and given the balanced approach to managing output with the SST-50 version, I am sure the M21 will prove the same. 

*Preliminary Observations*

I’ll get right to the point – I think Olight has another winner on its hands. :twothumbs

The M21 is really a direct port of the Luminus SST-50 to the M20 design, with a slightly larger head and revised reflector design to accommodate the new emitter. Otherwise, the body parts are interchangeable, and even the relative output levels are not so different (more on that in a moment). 

The M20 has a lot of “legs” in the flashlight world. I first reviewed it 15 months ago, yet it remains one of the better choices in the general purpose/tactical 2xCR123A market. Moreover, Olight has managed to keep the quality of construction and availability of extra options roughly constant over that time – which is something of a feat for this market.

The main advantages of the M21 over the M20 are due to the Luminus SST-50 emitter, and include greater output on Hi, smoother beam pattern, and (in my experience) lesser likelihood of extreme tints (especially green ones). Potential drawbacks to the M21 are the reduced throw (due to the larger emitter die), lower Med/Hi runtimes, and potentially greater heat.

Olight seems to have resolved the latter issue by not driving the M21 as hard as other Luminus SST-50-equipped lights (e.g. ThruNite Catapult, Lumapower Dmini VX Ultra). While you still get a significant output boost compared to the M20’s Cree XR-E R2, in my testing the M21 is no more than ~40% brighter overall (and perhaps less). Those expecting something closer to twice as bright will have to look at other lights.

But this is not a bad thing – personally, I am a little concerned about how heavily driven some of the other SST-50 lights are. Only time will tell, but I suspect Olight has struck a good balance in maximizing the life of the LED (and consequently the light) with a reasonable set of output levels (and thus heat). :thumbsup:

At the end of the day, the choice between the M20 and the M21 comes down to the differences in beam pattern and output. I don't know if there are enough compelling reasons to “upgrade” your M20 to a M21 – that’s your call - but I think new users will be happy with the build of either.


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## jhc37013 (Jan 8, 2010)

Very good review as always thankyou. I have seen and tested the Olight M20 Ti version and was wondering if you know of anything different about the Ti M20 and the M21. Everything points to them being the same inside. Thanks again your stuff is priceless.


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## DM51 (Jan 8, 2010)

Great work as always!

Olight have stuck with a good design and used the new emitter to improve the performance. I like your point that they haven't gone crazy and tried to wring the maximum possible output from it - that is a sensible approach. 2-3 years ago, no-one would have believed 500 lm from a light this size was possible. 

Moving to the Reviews section...


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## HKJ (Jan 8, 2010)

As always a nicely done review, but I have a few comments:

What are you showing on the oscilloscope trace, I would expect a flat line when you have no pwm (Not the strobe)?

The output matches my measurements on the M20 Ti (that was the predecessor to the M21). In this, rather small, light it is probably a good idea to run the SST50 at lower power levels, but in bigger lights I do not see any problems with running it at higher power.


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## sfca (Jan 8, 2010)

Quick question regarding perceived brightness:

If one was standing say 10ft out and within the hotspot _but_ on either side - not direct-center, which flashlight would be perceived as brighter the M20 or M21?


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## ARA (Jan 8, 2010)

:bow::bow::bow: Thanks mate for such a great review. Its always informative to read your reviews. appreciate your efforts. 

cheers


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## selfbuilt (Jan 8, 2010)

Thanks for the support everyone! :grouphug:



DM51 said:


> Olight have stuck with a good design and used the new emitter to improve the performance. I like your point that they haven't gone crazy and tried to wring the maximum possible output from it - that is a sensible approach. 2-3 years ago, no-one would have believed 500 lm from a light this size was possible.





HKJ said:


> In this, rather small, light it is probably a good idea to run the SST50 at lower power levels, but in bigger lights I do not see any problems with running it at higher power.


Yup, I think it is very sensible in this case. And it's true, the much larger ThruNite Catapult should be able to handle the higher power - it was the smaller D-mini VX Ultra I was thinking of in my comments (and other potential lights of this 2xCR123A-size class). 

FYI, my D-mini VX Ultra review should be up by end of day tomorrow ... 



HKJ said:


> What are you showing on the oscilloscope trace, I would expect a flat line when you have no pwm (Not the strobe)?


Ah, that's likely just noise in my setup. 

My oscilloscope is just a freeware piece of software that monitors my sound card's mic-in port ... and my high-tech probe is dollar-store microphone where I've stripped off the head and wired in a red LED instead. :laughing: I've also recently upgraded computers, and am just using the built-in sound features instead of dedicated card (used to run an SB Audigy), hence why things have likely gotten a bit "noisier".

And I enjoy your reviews too - keep 'em coming! 



sfca said:


> Quick question regarding perceived brightness:
> If one was standing say 10ft out and within the hotspot _but_ on either side - not direct-center, which flashlight would be perceived as brighter the M20 or M21?


If you mean around the edge of the hotspot (i.e. the corona), then no question - the M21 is brighter. Its hotspot is much broader, and illuminates an area about twice as wide by 10ft out. 

Just tested it with a lightmeter (since tint differences make it hard to judge by eye), and the difference is clear. Even if I move more toward the end of the respective hotspots, the M21 maintains an output advantage at all areas just outside the immediate centre-beam hotspot (where the M20 is of course brighter). I'll see if I can take some pics once it gets dark ... 

*UPDATE: *Here are some close-ups at 5m to better show you the hotspots. Both lights on Max on 18650. The height of each image is ~1.25m.














Pardon the spackle marks (this is from an unfinished part of my basement :laughing. But as you can see, the M21's hotspot illuminates an area about twice as wide as the M20 at 5m. The width of the hotspot is about 1m wide for the M21, half-a-meter for the M20, at this distance.


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## sfca (Jan 8, 2010)

Thanks!!!! :thumbsup:


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## Geban (Jan 8, 2010)

Thank´s for a great review!
Just got my M21, and I haven´t had the opportunity to try it out really yet.
But what I have tryed indoors, it seems to be a winner.


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## munchs (Jan 8, 2010)

Great review as always :thumbsup: Thanks!


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## Burgess (Jan 8, 2010)

to SelfBuilt --

:goodjob::kewlpics::thanks:
_


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## The Coach (Jan 8, 2010)

Thanks for the review. I'm glad, because I have one on it's way down the turnpike. :devil:


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## Olef (Jan 8, 2010)

Nice one Selfbuilt, excellent review as always. I've been waiting for this one!

One thing puzzles me. I know manufacturers routinely overstate runtimes etc, but Olight state - 

"Functions: Three brightness levels plus strobe, 20lm (30hrs)-80lm (8hrs)-500 lm (1.2hrs), Strobe(500lm/2.4h)"

Comparing Olight's stated medium 80lm for 8 hrs to your runtime graphs there is a huge difference. You got 2h34m on med with AW RCR's and 5h34m with 18650 neither of which comes close to Olight's claims. Furthermore, can Olight really be that cynical to quote maximum brightness figures on one hand with the optimum battery config of 2 x RCR and yet in the same sentence claim runtimes that have to be with 18650, giving much less brightness, and even then nearly double what you have measured?

Have you any idea what is going on here? Have Olight really overstated this light so badly or could the unit you have be flawed in some way? :thinking:

Olef


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## selfbuilt (Jan 8, 2010)

Olef said:


> Comparing Olight's stated medium 80lm for 8 hrs to your runtime graphs there is a huge difference. You got 2h34m on med with AW RCR's and 5h34m with 18650 neither of which comes close to Olight's claims. Furthermore, can Olight really be that cynical to quote maximum brightness figures on one hand with the optimum battery config of 2 x RCR and yet in the same sentence claim runtimes that have to be with 18650, giving much less brightness, and even then nearly double what you have measured?


I'd say it's a pretty sure bet they are using 18650 for their runtime estimates, and likely newer high-capacity 2600-30000mAh ones. I still use the older 2200mAh AWs, to allow backward comparison to my earlier data. With higher capacity 18650s, and taking into account variation in emitters, circuits, etc., those runtime estimates seem quite believable.

Not so sure about the actual lumen estimates ... although I know my lightbox is hardly linear above Med settings, I don't think Hi is really more than 6 times brighter than Med. Just a guess, but I'm thinking that 500 lumen estimate is a bit of an overestimate - something in 350-400 range (tops) is more likely. Similarly, the 80 lumen Med also seems like an underestimate (probably more like something in the 100-120 lumen range). The 20 lumen low sounds about right, but might actually be even a bit lower (which is why I haven't done runtimes - should last a long while). But someone with a calibrated light sphere would have to make those determinations - I'm just guestimating here.


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## applevision (Jan 8, 2010)

Outstanding as always, *Selfbuilt*!


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## Olef (Jan 9, 2010)

selfbuilt said:


> I'm just guestimating here.



And doing a superb job too, thank you. I look forward to every one of your reviews :goodjob:

I was just surprised by the disparity in the runtimes you achieved and those that Olight publish, and I guess a little disappointed in both Olight and the M21. That aside, I like my M21 a lot. It's well engineered, has a no-nonsense UI and chucks out a amazing amount of light for its size - plus its floody nature makes it so very useful for close / mid-range.

It's still going to be my bedside light, but now I might invest in extra AW cells so I can keep it running 

Olef


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## MattK (Jan 11, 2010)

Great job as always!

Olef - most factories use the highest capacity 18650's for runtime tests - 2600-3000mah is common. As selfbuilt points out he uses 2200mah in his tests so I'm not sure why you are disasspointed in Olight. Also, the factories often use unprotected batteries when doing these tests (Japanese 2800+mah 18650;s aren't tey available in protected form). 

Wouldn't you be using some of the highest capacity products to test your products to state the best possible runtime?


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## Geban (Jan 11, 2010)

Yesterday I tryed my new M21 at work for the first time, and it´s quite impressive.

Not the best thrower, but a whole lot of light.


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## Olef (Jan 11, 2010)

MattK said:


> Olef - most factories use the highest capacity 18650's for runtime tests - 2600-3000mah is common. As selfbuilt points out he uses 2200mah in his tests so I'm not sure why you are disasspointed in Olight. Also, the factories often use unprotected batteries when doing these tests (Japanese 2800+mah 18650;s aren't tey available in protected form).
> 
> Wouldn't you be using some of the highest capacity products to test your products to state the best possible runtime?



I certainly would try to show my product in the best light (lol) possible. I just find the stated medium of 8 hrs a bit too overstated based on Selfbuilt's excellent review. 5h20 on 18650 and 2h34 on RCR's are both a long way off 8hrs. That, to me, is a little like paying out for a 150mph sports car and finding under real world conditions it cannot even make the ton!

Especially as AW 18650's cost the equivalent of over $19 a pop in the UK :sigh:

Olef


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## MattK (Jan 12, 2010)

Well the key is that selfbuilt is using rather old 18650's - most everyone is using 2600mah + cells these days. Selfbuilt, as noted above has only stayed with the 2200's to lend his review runtimes consistency so it's not fair to fault the factory for that.


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## selfbuilt (Jan 12, 2010)

MattK said:


> Selfbuilt, as noted above has only stayed with the 2200's to lend his review runtimes consistency so it's not fair to fault the factory for that.


Quite true ... and quite daunting from my end to go back and re-test all those older lights with 2600mAh cells.  I have enough on my hands with all the new lights everyone keeps sending me. 

Also, manufacturer's rarely use time to 50%, most use a relative "useable" light measure. If you pick the time my 18650s were almost dead, then by a simple calculation based on my results, a 2800mAh cell should give you a good 7 hours runtime on Med, and a 3000mAh cell would give you 7.5 hours (assuming everyone is calculating the mAh rating the same way - a big assumption). Taking into account emitter and battery variation, 8 hours is not such a stretch.

But I suggest it might also be possible that Olight has slightly changed the output from initial spec (i.e. 80 lumens seems a little low to me, I'm thinking it's more like 110-120 lumens, based on other lights I've tested). If the output of the final shipping version is indeed a bit higher than what they originally tested, than could also easily explain the rest of the variance.

Note that I'm not "defending" anyone's runtimes estimates - I actually believe manufacturer's estimates should be largely ignored, and the average of what individual users report be taken as the best indicator. In the real world, n=1 is not very reliable.


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## MattK (Jan 12, 2010)

Heh, on the website we often use your data rather than the factories.


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## selfbuilt (Jan 13, 2010)

FYI, Mrs Selfbuilt has given the M21 a :thumbsup: in a little inpromptu field testing this evening (group walk). I gave her the option of the M21 or the D-mini VX Ultra on 18650, and she choose the M21 because she preferred the interface (doesn't like switching modes at the tailcap, prefers a head twist - she's a die-hard Fenix L2T fan )

Of course, she didn't need Hi - Lo and Med were fine. But I liked the thought that she had it there as a backup. Only thing she'd change is removing the strobe mode.


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## berry580 (Jan 14, 2010)

MattK said:


> Wouldn't you be using some of the highest capacity products to test your products to state the best possible runtime?


I think they should state what batteries they used to achieve the runtime. That should minimise conflicts.


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## MattK (Jan 14, 2010)

Perhaps but the only factory i know that ever does that is LumaPower.

Not one other factory that I can think of, in the whole world, tells you what battery they're using.

So, it's probably not a realistic expectation.


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## BUZ (Jan 14, 2010)

WOW, great review and pics!!!


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## wapkil (Jan 16, 2010)

MattK said:


> Perhaps but the only factory i know that ever does that is LumaPower.
> 
> Not one other factory that I can think of, in the whole world, tells you what battery they're using.



It's off topic in this thread but ZebraLight also publishes what battery they use for the runtime data. JetBeam does not but they answered when I asked.


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## SRB (Mar 10, 2010)

Awesome review! I love the beamwidth and spill. Looks like a suitable replacement for my TK11-r2 that ended up living in the wife's truck. Many thanks.


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## MaximusOrilius (Mar 11, 2010)

Just got my m21, the only other flashlight i have is an old LumaM1Hunter. My old LumaM1Hunter throws a little better but the m21 beats it everywhere else. Most of my work is up close and the farthest would be 100ft, so the m21 beats the LumaM1Hunter here for my use. 

At work I use it when i am under desks, walking into dark rooms and working in the ceiling. At home i use it for walks and when i get up in the morning looking for my clothes (dont want to turn on the lights and wake up my wife).


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## HIDblue (Apr 1, 2010)

Great review selfbuilt :thumbsup: Meticulous yet understandable by the not-so-technically inclined, like myself. 

I bought my first high-end flashlight (a JETBeam Jet-III M) primarily based upon your review, but am now getting the itch to buy the Olight M21 also based upon your review. You're killin me man! I swear to god, flashlights are like crack...one little taste and you're hooked (hypothetically speaking). 

Anyways, keep up the great work.


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## Disintergrator66 (Apr 16, 2010)

HIDblue said:


> Great review selfbuilt :thumbsup: Meticulous yet understandable by the not-so-technically inclined, like myself.
> 
> I bought my first high-end flashlight (a JETBeam Jet-III M) primarily based upon your review, but am now getting the itch to buy the Olight M21 also based upon your review. You're killin me man! I swear to god, flashlights are like crack...one little taste and you're hooked (hypothetically speaking).
> 
> Anyways, keep up the great work.


 
+1


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## klorsey (Jul 25, 2010)

So I'm no expert,but every time I've considered an Olight M-20/M-20s,I've been turned off by cpf stories about their their Li-ion 18650 (Hopeless) usage stat's.Do these problems continue with the M-21 torch model or not?


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## selfbuilt (Jul 25, 2010)

klorsey said:


> So I'm no expert,but every time I've considered an Olight M-20/M-20s,I've been turned off by cpf stories about their their Li-ion 18650 (Hopeless) usage stat's.Do these problems continue with the M-21 torch model or not?


Sorry, I have no idea what you mean. My reviews of the M20 and M21 show my experience on 2200mAh 18650, which I believe are about typical. Performance is certainly consistent with other current-controlled light.


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## picrthis (Aug 6, 2010)

Nice review, they list the light as 500 lumens, but does anybody know what the OTF rating really is?

Thanks


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## Golfer2000 (Aug 17, 2010)

can you remove the clip and the lanyard attachment/grip thing to reduce the profile?


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## picrthis (Aug 17, 2010)

Yes they are removeable.


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## selfbuilt (Mar 13, 2011)

> *Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
> Written by *jcalvert* on 12-22-2010 10:28 AM GMT
> 
> Hello Eric,
> ...




*Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
Written by *selfbuilt* on 12-22-2010 12:02 PM GMT



jcalvert said:


> However, I'm in search of a predominantly floody, mid-size (5"-7"), general purpose light such as I believe the M21 may be, within a $120 budget, that also offers enough useful throw (at least 50 yards+) to make it an ideal trail walking light in heavy woodslands. Would you be able to offer any other products to suggest that I could look further into that are predominantly flood-based lights of the type previously described that I may also consider, so that I can make a fully informed choice?


The The M21 is a good walking light in my opinion, due to the broad hotspot and good spill (i.e. I don't like playing "follow the bouncing ball" of a tight hotspot when walking at night). The Lumapower D-mini VX Ultra (SST-50) with 18650-tube is another good option for this type of beam (with optional TurboForce head if you want more throw).

But there are now a number of XP-G R5 lights you might also want to consider, like the Eagletac T20C2-II or Fenix TK12. These are not overly throwy, but do have a tighter hotspot than those above. 

Whatever light you go for, see if you can get a properly fitting diffuser for it. That way, you can have pure flood whenever you want.



> Second, is there a way to translate lux to feet or yards. For example, if you have measured the M21 SST-50 to have a lux measurement of 6,700, how can I translate that to feet or yards so that I know how far the light throws its beam and to also make accurate comparisons with other lights?


Yes, you can do this easily - but you have to decide what is a minimally acceptable lux level first. Yes, you can do this easily - but you have to decide what is a minimally acceptable lux level first.

The ANSI FL-1 standard "beam distance" is based on distance calculated to yield 0.25 lux. This is considered the ground level illumination of a full moon. The calculation is simple: divide lux at 1m by 0.25 (i.e. 6,700/0.25 in this case) and take the square root (to give you 163m in this case).

Personally, I find 0.25 lux to be rather low. More realistic might be to go with something between 1-5 lux as the minimum output need to make out what you are looking. 1 lux is simple - it is just the square root of lux at 1m (i.e. sqr-rt of 6700 = 82m). 5 lux would be the sqr-rt of (6700/5) = 37m. 

Again, it doesn't really matter which one you go with - as long as you are consistent in comparing lights.





> *Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
> Written by *jcalvert* on 12-23-2010 05:03 AM GMT
> 
> 
> ...



*Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
Written by *selfbuilt* on 12-23-2010 08:54 AM GMT



jcalvert said:


> My question finally is this, why do you think ET would not have placed the low mode in with the constant light group so that owners could set the memory to low?


No interface is perfect - I guess they didn't attach as much weight to that option. No interface is perfect - I guess they didn't attach as much weight to that option. :shrug: Personally, I like a light that comes on in moonlight mode (for middle of the night). But I still find the T20C2-II an excellent dog-walking light (in General mode, with option for Turbo when you need it).



> I will likely just use the simple 1 lux measurement initially and when I receive the M21, I'll measure out 82' and with my son's help, see how much detail I can make out on him at that distance to determine if using 1 lux is just right or if I need to adjust my basis lux number up or down based on the amount of detail I can make out with my eyesight.


Let us know how it works out for you! Curious to hear your findings. And happy holidays to you as well. Let us know how it works out for you! Curious to hear your findings. And happy holidays to you as well. :wave:




> *Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
> Written by *jcalvert* on 12-27-2010 07:11 PM GMT
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*Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
Written by *selfbuilt* on 12-27-2010 09:14 PM GMT



jcalvert said:


> The question is, based on your expertise and knowledge of the T20 and the G5, do you think either or both of these XM-L upgrades, if they happen, will provide a broader flood hotspot and also more throw than the M21.


Hard to say without seeing them. But in general terms, the XM-L has a smaller die size than the Hard to say without seeing them. But in general terms, the XM-L has a smaller die size than the SST-50, so it should throw further with a standard-size reflector (although that depends on the specific reflector design). The G5 is designed for throw, so I expect a XM-L version would be relatively throwy. But there are a lot of unknowns, until the lights are actually produced.





> *Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
> Written by *jcalvert* on 12-28-2010 05:11 PM GMT
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*Re: Olight M21 ( Luminus SST-50 ) Review : RUNTIMES , BEAMSHOTS and more !*
Written by *selfbuilt* on 12-29-2010 09:26 AM GMT



jcalvert said:


> Well I guess I have hopefully just one last question that may help me out. Since we have lumens to measure output and lux to measure throw, do we have some designation for flood that I can research and use to make apples-to apples comparisons between lights? Thank you!


The simplest measure is simply the ratio of throw (square-root lux) to output (lumens, or some such). The lower that ratio, the less the light is focused for throw (and hence, The simplest measure is simply the ratio of throw (square-root lux) to output (lumens, or some such). The lower that ratio, the less the light is focused for throw (and hence, more floody).

Of course, that tells you nothing about the overall spillbeam width - for that, you need to check comparative beamshots taken under the same conditions/distance. For most people, "flood" indicates how bright the spillbeam is relative to the center-beam hotspot. But hard to come up with an a simple measure - best is to look at the actual beamshots.


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## selfbuilt (Mar 13, 2011)

The thread discussions for the last few months have been *fully restored* from the search engine cache data (thank you tandem!).

Please carry on!


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## GreasySideDown (May 26, 2011)

I bought two of these flashlights, one for me, one for the wife, based upon this review. I am more than satisfied with both lights. She was a victim of assault a few years ago and now she carries a taser most places and this flashlight all places. I have owned a number of cheapo China lights and this thing is built to a much different standard. Strong, bright, and small. I run both lights on recycled laptop batteries so never have to pay for batteries.


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## DivineStrike (May 27, 2011)

Hey selfbuilt, quick question for ya as you've used a large variety of lights... Do you know, or have you tried using the M30 extension tube on the m20 sized lights and does the light still work?


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## selfbuilt (May 27, 2011)

DivineStrike said:


> Do you know, or have you tried using the M30 extension tube on the m20 sized lights and does the light still work?


Well, the diameter and threading is the same, so you can certainly screw the M30 extension tube on the M20/M21 (at least my samples, which are all from early production runs - things may have changed since then). But I have not tried activating the lights, since I am not sure what battery source would fit such a setup (maybe 2x18500?). The circuits for the M20/M21 are voltage limited, so 3x cells would likely blow the circuits. Frankly, there's little advantage to 2x18500 over 1x18650 (especially with newer high capacity 18650 cells), so there's really no point in doing this.


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