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

Originally posted: January 8, 2010
Last revised: March 13, 2011

Warning: pic heavy, as usual.

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

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. 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 ). 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.

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.

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).

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.

To follow the online discussions for this review, please see the full review thread at CPF.




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