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



## selfbuilt (Dec 3, 2010)

*Warning: pic heavy, as usual. *







*Specifications:*

LED: Cree XP-G R5 
Lighting mode: 140 lumens (1.5hrs) - 60 lumens (4.8hrs) - 12 lumens (25hrs) - 2 lumens (83hrs)
Flashing modes: SOS - (60 Lumen, 13.4hrs) - Beacon (60 Lumens, 70hrs) - Variable frequency strobe (140 Lumens, 3hrs)
Runtimes based on SANYO 2500mAh Ni-MH battery.
Working Voltage: 0.9V-1.8V
Battery: 1pc 1.5V AA (Alkaline, Ni-MH, Lithium)
Tactical tail switch for power on and off with momentary activation
Side switch for adjusting brightness output
Rotate the flashlight head to access hidden modes (Super Low, SOS, Beacon)
Strobe access: Press and hold the side switch for 0.5 seconds in any mode
Lens: Toughened ultra-clear glass
Material: Aircraft grade aluminum
Dimensions: 107mm (Length) x 25.3mm (Head) x 20mm (Body)
Net weight: 53g (Excluding battery)
Waterproof to IPX-8 Standard
Intelligent memory function (memorizes the last used lighting mode)
High-efficiency digitally regulated output - maintains constant brightness
Reverse polarity protection
One hand operation
Included accessories: holster, lanyard, body clip, two spare o-rings, and a rubber switch boot
Estimated MSRP ~$58
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 … 

*Output/Runtime Comparison:*




























Output/runtime performance is outstanding. oo:

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. oo: 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.


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## selfbuilt (Mar 10, 2011)

> Written by *tandem* on 12-03-2010 06:28 PM GMT
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> Written by *GoingGear.com* on 12-03-2010 07:17 PM GMT
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> Written by *selfbuilt* on 12-03-2010 08:21 PM GMT
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> Written by *tandem* on 12-03-2010 10:01 PM GMT
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> Written by *Burgess* on 12-03-2010 11:02 PM GMT
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> Very interesting flashlight.
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> Written by *GoingGear.com* on 12-03-2010 11:29 PM GMT
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> Written by *Russ Prechtl* on 12-04-2010 11:15 AM GMT
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> +1 on a great review! Thanks. Another great one for the collection. :thumbsup:
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> BTW - I also hate the fast strobes. :thumbsdow





> Written by *Acid87* on 12-04-2010 11:44 AM GMT
> 
> As always a really well done review in depth and to the point. I was really intrigued by the new Klarus lights but was too scared to make the plunge. Thanks think I know what im getting for xmas! :thumbsup:





> Written by *RBWNY* on 12-04-2010 07:13 PM GMT
> 
> Hi! Loooooooong-time browser, first-time poster!! I'll skip the formal introductions for now, by simply announcing that due to the excellent review of the ST10... I just ordered an ST20 :naughty:
> 
> I'll post my findings, and perhaps compare it to my EagleTac P20A2 MKII, which seems similar in brightness and build quality. I have a feeling though, that I'm gonna like the Klarus better!! (I hope)


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## selfbuilt (Mar 10, 2011)

_Written by *selfbuilt* on 12-05-2010 10:02 AM GMT_

Glad you are all enjoying the review. :grouphug:



GoingGear.com said:


> I know I live in the south and we like our guns and other crippling weapons here, but I get the strobe question from people all over the country and even the world. Trust me, a lot of people want a fast strobe. There seems to be a lot of appeal in a light that doubles as a self defense tool.


Interesting. And no doubt, my perspective is shaped by the fact that I'm a Canadian (not too many firearms up here). Interesting. And no doubt, my perspective is shaped by the fact that I'm a Canadian (not too many firearms up here).  But I would like to see fast beacon (i.e. 1-3 Hz), overall the more common slow beacon (i.e. 0.1 Hz) or fast strobe (>10 Hz).

Whenever I show my lights around to the un-initiated, the fast strobe is always what initially "impresses" them the most (followed by a continuously-variable interface). But when asked what model they would prefer for their own use, they invariably want something with a small number of constant output modes, and maybe a blinking/beacon mode. I suppose perhaps the difference is that these folks wouldn't be surfing the web looking for dedicated flashlight dealers. So I can see there would some demand for "tactical" strobes from the high-end flashlight crowd.



> The one that I have never, ever had anyone specifically request is SOS.


That I can believe! That I can believe!



> Regarding AA lights for tactical uses, that is another top request from LEOs around here. A lot of the departments in the area give their officers free AAs instead of CR123s, so they look for AA lights. One of the local fire departments is outfitted with Fenix LD20s.


Hmm, another interesting cultural difference. I'm always checking out the gear on any LEO/EMTs I see, and notice they tend to carry Pelicans/Streamlights/Mags, often the models with dedicated chargers (likely NiCd, ugh). Stingers seem especially prevalent on EMTs for some reason. A number carry what I'm guessing are their own personal 2xCR123A-based light. I wouldn't be surprised if a number are also carrying personal AA-based lights as a backup (e.g. on their belts). But again, the few I've actually spoken to about it have told me they don't use strobe modes at all (this later group is a small sample size, I admit). Hmm, another interesting cultural difference. I'm always checking out the gear on any LEO/EMTs I see, and notice they tend to carry Pelicans/Streamlights/Mags, often the models with dedicated chargers (likely NiCd, ugh). Stingers seem especially prevalent on EMTs for some reason. A number carry what I'm guessing are their own personal 2xCR123A-based light. I wouldn't be surprised if a number are also carrying personal AA-based lights as a backup (e.g. on their belts). But again, the few I've actually spoken to about it have told me they don't use strobe modes at all (this later group is a small sample size, I admit).


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## selfbuilt (Mar 10, 2011)

> Written by *LetThereBeLite* on 12-05-2010 10:07 AM GMT
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> Great review Selfbuilt!
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> Written by *LetThereBeLite* on 12-05-2010 10:21 AM GMT
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> *GoingGear*, sorry for not mentioning your outfit in my review. As I mentioned two other retailers, I should have mentioned you too.  My bad. LOL





> Written by *selfbuilt* on 12-05-2010 01:56 PM GMT
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> Written by *tandem* on 12-05-2010 02:21 PM GMT
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> Nice video LetThereBeLite! Forward clickies with momentary activation are a hot button for me (pun intended); I wish more lights had these. I'm not convinced I like the idea of two-buttons on flashlight, especially one this small. My concern is regarding durability - two moving parts to go wrong, not just one; two points of water or material ingress, two boots which can fail. Perhaps the click-load being distributed between two switches will help in this regard. But from a usability perspective, I'd prefer to control the light with one hand.
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## selfbuilt (Mar 10, 2011)

_Written by *selfbuilt* on 12-06-2010 06:23 PM GMT_



tandem said:


> selfbuilt - are there any build aspects of this light that make you want to think it was produced in the same factory (or by the same designer) as the Zebralight flashlights? The head detail on the side of the front clicky is somewhat familiar looking, as is the front clicky visual appearance itself.


Hmmm, hard to say. Although the electronic switch feel is (superficially) similar, the overall design doesn't really remind me of Zebralight. But it's virtually impossible to know from the outside - the relationship between Chinese manufacturers is complex, and there is a lot of contracting out work. Hmmm, hard to say. Although the electronic switch feel is (superficially) similar, the overall design doesn't really remind me of Zebralight. But it's virtually impossible to know from the outside - the relationship between Chinese manufacturers is complex, and there is a lot of contracting out work. :shrug:

I'm more confident in thinking the circuit designer is related to Fenix somehow, given the runtime traces. As for the rest, your guess is as good as mine!


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## selfbuilt (Mar 10, 2011)

> Written by *bodhran* on 12-07-2010 09:39 AM GMT
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> Great Review Selfbuilt. My wife was looking over my shoulder while I was reading this and decided that this was the light for her. Surprised me, because she has never showed much of an interest in my flashlights. That's one Christmas present out of the way. *lol* I just hope she shares as I kind of like this one too.





> Written by *selfbuilt* on 12-07-2010 05:15 PM GMT
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> Written by *RBWNY* on 12-08-2010 08:03 PM GMT
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> Has anyone noticed?
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> Written by *Light1* on 12-09-2010 01:44 AM GMT
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> Very Nice Reivew.  Iam New here so im glad to be apart of a nice Forum.





> Written by *LetThereBeLite* on 12-09-2010 03:46 AM GMT
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> Written by *RBWNY* on 12-09-2010 01:06 PM GMT
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## selfbuilt (Mar 10, 2011)

_Written by *selfbuilt* on 12-09-2010 03:30 PM GMT_

FYI, the Klarus NT20 I currently have in testing also has a very noticeable difference between Lo and Super Lo.

For the ST10 tested in this review, I would estimate the Lo to be ~10-11 lumens, and the Super Lo to be ~1 lumen.

The physical dimensions of my sample were also measured with a digital caliper and digital scale, and are very consistent with reported specs.

The manual with both my ST10 and NT20 are correct in terms of the mode sequence. They are both listed as "High-Low-Mid" (which is another way of saying "Low-Med-High", since the light continues in repeating loop).


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## selfbuilt (Mar 10, 2011)

> Written by *LetThereBeLite* on 12-09-2010 05:08 PM GMT
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> Written by *RBWNY* on Unknown
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> Since I was not able to begin a new thread, I'll just add to this by reporting on the arrival of the Klarus ST20 I ordered.
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## selfbuilt (Mar 10, 2011)

The main review post has been updated with the final review text.

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

Please carry on!


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## coachclass (Apr 10, 2011)

Selfbuilt,
I'm surprised the Klarus only ran for 2 hours at medium mode. The Zebra so much more efficient (at half the lumens, but over 3 times the run time)

In high mode with the eneloop, the zebra seems to out perform for runtime at about the same lumens as the Klarus. Although the caption saids 1hr26 for Klarus and 1hr37 for Zebra, the zebra graph just looks farther ahead.

What do you think of the relative efficiency between the Klarus and the Zebralight? Out of the batch, I would pick these two as the front runners for efficiency (runtime vs lumens). But the Zebralight still seems more efficient than the Klarus.


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## selfbuilt (Apr 10, 2011)

coachclass said:


> I'm surprised the Klarus only ran for 2 hours at medium mode. The Zebra so much more efficient (at half the lumens, but over 3 times the run time)


Ah, but that's not half the lumens on Med - it's a third. My relative lighbotx output scale is not linear for lumens. If you do the power reationship conversion factor described in the method section of my review, you will see the difference is actually more like ~105 lumens (for ST10) compared to ~35 lumens (for ZL). You really can't make meaningful overall light efficiency estimates with a 3-fold output difference, as emitters run much more efficiently as lower output. 



> In high mode with the eneloop, the zebra seems to out perform for runtime at about the same lumens as the Klarus. Although the caption saids 1hr26 for Klarus and 1hr37 for Zebra, the zebra graph just looks farther ahead.


Thanks, I'll fix the caption the next time I have my data files open. But again, I wouldn't consider the lumen level to be so equivalent. The ST10 is somewhat in-between the ZL Hi1 and Hi2, and runs very well for the class. It is just that the ZL is exceptionally good for this class at its high output levels - likely because ZL specifically adjusted the circuit to optimize for NIMH. 

It's hard to know how they would compare at the lower levels (which I don't test because of time involved, and greater variability due to small changes in emiter Vf). But my experience tells me the Klarus/Fenix circuits would likely have the advantage over the PWM-based ZL (even with its NiMH optimizations) at low-level outputs.



> What do you think of the relative efficiency between the Klarus and the Zebralight? Out of the batch, I would pick these two as the front runners for efficiency (runtime vs lumens). But the Zebralight still seems more efficient than the Klarus.


Both are exceptionally good performers in this class. Honestly, I wouldn't base a purchasing decision on minor differences in efficiency - I would go with build and UI preference in this case.


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## Mikellen (Apr 10, 2011)

Hi selfbuilt, you mentined that the Klarus has an electronic switch. Will that mean that the Klarus has "parasitic drain" on the battery?
If so do you know how much? For example, Zebralight acknowledges their lights with electronic switches have "parasitic drain" and provides the number of years it would take to drain the battery.

Thanks.

Also in your low mode Duracell alkaline runtime graph in this thread and the Xeno E03 thread, the Klarus is stated as 2 hrs. 49 minutes. Should that read 20 hrs. 49 minutes?


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## selfbuilt (Apr 10, 2011)

Mikellen said:


> Hi selfbuilt, you mentined that the Klarus has an electronic switch. Will that mean that the Klarus has "parasitic drain" on the battery?
> If so do you know how much? For example, Zebralight acknowledges their lights with electronic switches have "parasitic drain" and provides the number of years it would take to drain the battery.


No, there is no standby drain on the Klarus lights, because they use a tailcap clicky switch. Standby drains are only needed in electronic devices that need to be receiving power at all times to respond to an electronic command. The Klarus mode switch only works when there is power to to the device, controlled by the clicky.



> Also in your low mode Duracell alkaline runtime graph in this thread and the Xeno E03 thread, the Klarus is stated as 2 hrs. 49 minutes. Should that read 20 hrs. 49 minutes?


Thanks, that is a typo - I'll correct it next time I have the data files open.


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## pascual (Apr 17, 2011)

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: 



Selfbuilt - so how would you like to have seen the modes/lumens spaced? The two highest output, 60 and 140, you are saying there is little difference between these two outputs?


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## selfbuilt (Apr 19, 2011)

pascual said:


> Selfbuilt - so how would you like to have seen the modes/lumens spaced? The two highest output, 60 and 140, you are saying there is little difference between these two outputs?


Personally, I prefer the Fenix spacing (i.e. I like the Med mode), but I also like the extra moonlight on ther ST10. :shrug:

In this case, I find the ST10 Med mode is actually closer to ~100 estimated lumens (with ~160 for Hi, ~8 for Lo, and ~1 for Moonlight). That is a pretty big difference between Med and Lo.


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## pascual (Apr 20, 2011)

I see - just to clarify, (as you can see, I am new to all this based on my number of posts etc.), eventhough Klarus manufacturer says the Med mode should be 60, it is actually about 100 lm, making the jump from 100 med to 160 hi, not that big of a difference. HOWEVER, should the flashlight really produce what it says it should produce, 2 moonlight, 12 lo, 60 med, and 140 hi, you would like it. Is that correct?

Also, i have read all your acticles about definitions of relative light output,beam distance, etc. and I think get understand or get the gist of it - however, I am still confused about *Peak Throw ([email protected]). For the ST10, it says the Peak Throw ([email protected]) is about 1800. based on your definition, I am still confused on what it means or how to interpret/use that information. Like is 1800 the lux/candela or can I convert it to lumens etc.?? sorry for the newbie question.*


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## nikoncoolpics (Apr 20, 2011)

This is an amazingly detailed review. absolutley first class. I look forward to more like it.


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## selfbuilt (Apr 21, 2011)

pascual said:


> For the ST10, it says the Peak Throw ([email protected]) is about 1800. based on your definition, I am still confused on what it means or how to interpret/use that information. Like is 1800 the lux/candela or can I convert it to lumens etc.?? sorry for the newbie question.[/SIZE][/FONT][/B]


The 1800 is indeed lux at 1m, which is the same as candela at 1m. Lux cannot be converted to lumens, as they are completely different (and independent). Lux is a measure of peak output at one point (the centre beam) and lumen is a measure of total overall output (captured in an integrating sphere). Lux is thus heavily dependent on the optics and focusing of the light, lumens should be independent of that.

In terms of throw, lux at 1m cannot be directly compared to other lights, since lux is a non-linear scale for distance (i.e. varies by an inverse-square law, for a point source of light). That is to say, a light that is moved to half the distance to the lightmeter will give you a lux reading that is four times higher. The only way to compare throw between lights is to normalize the data by taking a square root of the lux at a given distance. This is what ANSI FL-1 standard does as "beam distance", which is the distance (in meters) to when 0.25 lux would be measured. It allows you to directly compare the throw of different lights.

EDIT: Text edited to remove the output reference - I am referring just to the non-linearity of lux for distance.


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## pascual (Apr 21, 2011)

Selfbuilt

Thank you for taking the time to answer this newbie question - what you said really helps make sense of the other articles I read that you wrote about this topic. You da man!!







selfbuilt said:


> The 1800 is indeed lux at 1m, which is the same as candela at 1m. Lux cannot be converted to lumens, as they are completely different (and independent). Lux is a measure of peak output at one point (the centre beam) and lumen is a measure of total overall output (captured in an integrating sphere). Lux is thus heavily dependent on the optics and focusing of the light, lumens should be independent of that.
> 
> In terms of throw, lux at 1m cannot be directly compared to other lights, since lux is a non-linear scale (i.e. varies by an inverse-square law). That is to say, a light that has an output mode that is twice as bright will give you a lux at 1m score that is four times higher. The only way to compare throw is to normalize the data by taking a square root of the lux at 1m. This is what ANSI FL-1 standard does as "beam distance", which is the distance (in meters) to when 0.25 lux would be measured. It allows you to directly compare the throw of different lights.


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## HKJ (Apr 21, 2011)

selfbuilt said:


> In terms of throw, lux at 1m cannot be directly compared to other lights, since lux is a non-linear scale (i.e. varies by an inverse-square law). That is to say, a light that has an output mode that is twice as bright will give you a lux at 1m score that is four times higher.



You have it backwards here, lux is the linear quantity, throw is the non-linear quantity. Double current in a led and you get (roughly) double power consumption, double lux, double lumen and 1.4 times the throw.
I.e. everything follows a linear relationship, except throw (The led conversion of current to brightness is not completely linear).


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## selfbuilt (Apr 22, 2011)

HKJ said:


> You have it backwards here, lux is the linear quantity, throw is the non-linear quantity. Double current in a led and you get (roughly) double power consumption, double lux, double lumen and 1.4 times the throw.
> I.e. everything follows a linear relationship, except throw (The led conversion of current to brightness is not completely linear).


Yes, you are right - I was thinking only of the non-linearity of lux for distance comparisons (i.e. "throw"), but instead wrote for an output comparison in that sentence. I will revise that - I meant to say for half the distance (not twice the output), lux will score will be four times higher.


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## jamjam (Sep 4, 2011)

Hi Selfbuilt, do you think the ST10 will be able to "LEGO" with the rest of this series (ST20, NT10) like the Fenix LD and Quark Family? I couln't find any info regarding this anywhere online. May be not the NT20 since the voltage range will be diffirent than the rest. Any hint?


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## selfbuilt (Sep 4, 2011)

jamjam said:


> Hi Selfbuilt, do you think the ST10 will be able to "LEGO" with the rest of this series (ST20, NT10) like the Fenix LD and Quark Family? I couln't find any info regarding this anywhere online. May be not the NT20 since the voltage range will be diffirent than the rest. Any hint?


Don't know about the other members of the family, but the ST10 and NT20 won't lego (i.e. the battery tube diameter is different, so heads and tails are not interchangeable).


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## jamjam (Sep 4, 2011)

selfbuilt said:


> Don't know about the other members of the family, but the ST10 and NT20 won't lego (i.e. the battery tube diameter is different, so heads and tails are not interchangeable).


 
Thanks for the quick reply. I can't get hold of any 4Seven light here in Beijing, but chinese brands like Fenix, Jetbeam, Sunwayman, Klarus etc are a lot cheaper to buy locally. Thats why I am asking for the Klarus, may be I should get the LD20 and LD10 to replace my old Q5 version.


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## Titanium81 (Oct 20, 2011)

Is that a Ti clip that it comes with?


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## sog_sniper (Oct 27, 2012)

The more I read, the more I understandand lighting terminologies.... Thank you to all for sharing these informations....


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