Klarus ST10 (1xAA, XP-G R5) Review: RUNTIMES, BEAMSHOTS PICS, and more!

Originally posted: December 10, 2010

Warning: pic heavy, as usual. :whistle:


Kalrus is a new maker on the scene, and the ST10 is their first 1xAA model. Note the specs show support for standard batteries (NiMH/Alkaline/L91 lithium) only – 14500 is not supported.

Packaging is fairly standard, but the light comes with a good number of extras. Inside the cardboard box with plastic insert is the light, manual, spare o-rings, extra boot cap, wrist strap, pocket clip, and belt holster (with closing flap).

From left to right: Duracell AA, Klarus ST10, Fenix LD10-R4, ITP SA1, Zebralight SC51, Nitecore D10SP

ST-10: Weight: 53.0 g (no battery), Length 107.6mm x Width 22.5mm (bezel) 25.2mm (near switch)

Build quality is excellent. Note the square-cut threads at both ends of the battery tube. Screw threads are anodized at the tailcap for lock-out. :thumbsup:

The switches both have a good feel. The tailcap switch is a typical forward clicky, and the side switch feels like an electronic switch (but with better than typical feedback).

My sample tailstands, but barely (i.e. it is quite wobbly). I suspect some adjustment of the clicky might help. I note that my Klarus NT20 sample (currently in testing) tailstands with virtually no wobble.

Light feels reasonably solid, if a bit top-heavy. Knurling is not very aggressive, but there are a lot of body ridge details to help with grip.

Anodizing is excellent on my sample, no chips in the flat black finish (HA = type III). Lettering is sharp and clear, nice and bright against the black background.

Clip seems to be fairly sturdy and good quality. It holds onto the light well, and can be positioned for bezel-up or bezel-down carry. But with all clips of this sort, these is always a risk the light might catch on something and be pulled off. The included holster seems good quality, and comes with a closing flap.

The ST10 features the Cree XP-G R5, with a medium textured orange peel (MOP) deep reflector.

Which brings us to the requisite white wall hunting ;). All lights are on Hi on Sanyo Eneloop, about ~0.75 meter from a white wall (with the camera ~1.25 meters back from the wall). Automatic white balance on the camera, to minimize tint differences.

From now on, all my beamshots will be taken in this standard configuration, to facilitate comparisons.

As you can see, the ST10 has a nice and reasonably smooth beam for this class. Scroll down to my Summary Tables for more specifics on output.

User Interface

The UI is fairly unique on these Klarus lights.

Turn the light on by pressing the tailcap clicky (press for momentary on, click for locked on).

With the head fully tightened, you get the regular modes. Press and release the side switch to change output levels. The output mode will change in the following sequence Lo > Med > Hi, in repeating order. The light will memorize the last mode used, and return to it upon re-activation.

With the head loosened (turn 1/8 turn counter-clockwise), you get the “Hidden” modes. Using the side switch, the output sequence is Super Lo > SOS > Beacon, in repeating order. Note there is no memory feature for the Hidden modes – the light will always come on in Super Lo (aka moonlight) upon activation with the head loosened.

Strobe is accessed from either mode state by pressing and holding the side switch for longer than half a second. As long as you hold the switch down, you will get a constant strobe mode. Release the switch, and a variable frequency strobe continues until you turn off the light or change modes (use the side switch to change to modes). Scroll down for the frequencies.

An interesting variant on the classic Fenix/4Sevens interface.

PWM and Strobe

The ST10 is current-controlled on its regular output modes (Lo, Med, Hi). It is just the “Super Lo” (aka moonlight) mode that uses PWM:

PWM on Super Lo is 120 Hz.

This is thus similar to the Zebralights, where current-control is used for regular modes (for max efficiency), and PWM is used for “moonlight” (for extended runtime at much lower output). :thumbsup:

If you press and hold the side switch, the light strobes at a constant frequency of 18.4 Hz. Once you release the switch, however, the light continues to strobe at an oscillating pair of frequencies:

The light spends ~1.8 secs at 18.4Hz, followed by the same length of time at 7.2Hz, in a reoccurring cycle. Not sure of the point of this, but it is certainly annoying! :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 any extended run Lo/Min modes (i.e. >12 hours) which are done without cooling.

I have recently devised a method for converting my lightbox relative output values (ROV) to estimated Lumens. See my How to convert Selfbuilt's Lighbox values to Lumens thread for more info.

Throw/Output Summary Chart:

Effective November 2010, I have revised my summary tables to match with the current ANSI FL-1 standard for flashlight testing. Please see http://www.sliderule.ca/FL1.htm for a description of the terms used in these tables.

The max output of the ST10 is very similar to the Fenix LD10-R4 (with a slight bump in output, likely due to the R5 emitter). Super Lo is much lower, thanks to the PWM (roughly equivalent to Lo2 of the Zebralight SC51).

I’ll have more to say on output levels after the runtimes … :whistle:

Output/Runtime Comparison:

Output/runtime performance is outstanding. :ooo:

Basically, the ST10 performs at least as well as the Fenix LD10 would do with a R5 instead of an R4. More than that, the output levels of the ST10's Lo/Med/Hi map exactly to the LD10 in the following way:

ST10 Hi = Fenix LD10-R4 Turbo
ST10 Med = Fenix LD10-R4 Hi
ST10 Lo = Fenix LD10-R4 Lo

Basically, you are missing the LD10’s Med mode, but you get the equivalent of the 4Sevens Quark Moonlight mode instead.

I can thus only conclude that the ST10 is using a hybrid of the Fenix LD10 circuit (sans Med mode) combined with PWM for Super Lo/Moonlight.

Potential Issues

My ST10 sample is a bit wobbly, but my NT20 sample tailstands with no problem. Adjusting the switch/boot cover may help in cases where tailstanding is not perfect on these Klarus lights.

Need to switch grip to change modes after turning on (i.e. rear tailcap for on-off, side switch for modes).

Strobe can be accidentally accessed if you hold down side switch too long while trying to change modes (i.e. greater than 0.5 secs).

Preliminary Observations

I seem to be seeing a rash of new makers lately - with surprisingly mature builds and circuit designs. The Klarus ST10 is another good example of this phenomenon – a solid light, with excellent performance and a somewhat novel interface. :)

The physical build of the light suggests a quality manufacture. There are a lot of nice design touches, and the light feels reasonably well balanced (maybe a little top heavy, accentuated somewhat by the narrower battery tube). Switch design seems good at both ends, with a good feel to both the rear on/off forward clicky switch and side level-changing electronic switch.

Mode changing is a little unusual, but should quickly become familiar to those used to the regular Fenix/Olight/4Sevens series (i.e. the head tight/loose for different mode sets). The main difference is the use of the side switch to select the levels within each set instead of the tailcap (i.e. like the ITP SA/SC series, or Lumapower MVP).

I found the UI quickly became intuitive (e.g. upon activation, head loose gives Super Lo, head tight for a memorized and selectable Lo/Med/Hi). I like the fact that you can ignore the various blinking modes if you don’t want to see them. One quibble here – 0.5 secs isn’t very long, and you may strobe yourself while changing output levels if you don’t release the side-switch fast enough. Also, what’s up with the oscillating two-freq strobe mode? :thinking: I wish makers would dispense with uber-annoying strobe modes, and simply give us a nice, simple slow (~1-2 Hz) signaling strobe. :sigh:

Output/runtime efficiency is one area where this light really performs. In fact, the specific output/runtime characteristics on Lo/Med/Hi are identical to the current-controlled Fenix LD10-R4's Lo/Hi/Turbo. :ooo: Coupled with the PWM-based Super Lo/Moonlight, you really get a good combination here.

But another quibble – I can understand dispensing with the Fenix-like Med on the other models in the Klarus line, but on the ST10 (like the LD10) this means you will see little difference between its two highest output levels. I don't know what the 2xAA Klarus is like (maybe it uses the same head as the ST10, like the Fenix LD20/LD10?), but I would have liked to seen levels spaced differently on the 1xAA version. :shrug:

All-in-all, this is an impressive first offering from a new manufacturer. I’m particularly glad to see the efficiency of a current-controlled Fenix-like circuit integrated with a Moonlight/Super Lo mode (although the latter is PWM-based in this case). Along with a number of innovative design features, I imagine Klarus will be attracting a fair amount of attention here.


ST10 provided by goinggear.com for review.

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

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