# ReviewTheLight: Nitecore SRT3 Defender



## Bigmac_79 (Oct 30, 2013)

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Nitecore has long been on the cutting edge of flashlight technology, and they're not slacking off now. As one of the first to adopt magnetic control ring technology, they're exploring it's capabilities with their new SRT series. The SRT series lights use the control ring not only for infinite variability, but for various utility modes and control of multi-color emitters. This review covers the smallest of the SRT's, the SRT3 Defender, powered by a single 16340 or 14500 sized battery, utilizing a Cree XM-L2 and a single small red/blue emitter.



_
Thanks to Nitecore for providing the SRT3 for review._

I’ll be reviewing the SRT3 in two sections: first, I’ll discuss the light objectively (the facts about the light itself), then I’ll discuss the light subjectively (my impressions about the light's performance when used for specific applications). If you have any other specific applications you'd like the light tested for, let me know and I'll see what I can do.

Video Review

Below is a video review of the SRT3. Due to my old image hosting site closing down, I've got new restrictions on image uploads and have replaced the "Construction" section of my reviews with a more detailed video review.


_This video is available in 1080p HD, but defaults to a lower quality. To select the playback quality click the settings button (looks like a gear) after you've started the video._


Objective

*Manufacturer's Specifications*

Price: 90 USD






Dimensions













*User Interface*

The interface of the SRT3 has many options, but is incredibly intuitive. To turn the light on/off, you use the tail switch at the rear (half-press for momentary on or full press for constant on), and to control the output you use the control ring.

With the light pointing away from you, turning the ring all the way to the left will start you in the Beacon mode, steady quick bright flash at low frequency. Turning right, you next get the SOS mode, then a Red/Blue Strobe, then Blue, then Red, then the Minimum White output, then a smooth Infinitely Variable transition up to the Maximum White output, then a high-frequency Strobe. Each of these positions has a detent in the control ring so it feels like a soft "click" into position, providing tactile feedback and prevent the ring from changing position in you pocket. The exception is the Infinitely Variable section, which has a detent on either end for the Min and Max output, but is smooth in between.


*Action Shots*

You can click on any of these shots to see them full size.

Light in Hand (without and with AA extender)






White Wall (Low, Medium, High, Blue, Red)
_ISO 100, f/3.3, 1/20" 
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(Blue and Red at 2")

BeamSlice








MugShot








Indoor Shots (Low, Medium, High, Blue, Red)
_ISO 100, f/3.3, 1"
_










(Blue and Red at 10")

Outdoor Shots (Low, Medium, High, Blue, Red)
_ISO 100, f/3.3, 2.5"
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Long-Range Shots (High)
_ISO 100, f/3.3, 5"
_


*Performance*

Submersion: I submersed the SRT3 under a foot of water for an hour, using the switch and control ring during that time, and found no evidence of water damaging or entering the light.

Heat: The SRT3 doesn't display any significant heat buildup.

PWM: 

Drop: I dropped the SRT3 on various surfaces (carpet, grass, packed dirt, hard wood) and it did not suffer any cosmetic or functional damage.

Reverse Polarity Protection: The SRT3 uses mechanical reverse polarity protection to prevent the negative terminal of a battery from making electrical connection with the head.

Over-Discharge Protection: The SRT3 does turn itself off before over-discharging a lion, but as always, I recommend recharging the battery before this is necessary. The output of the SRT3 drops slightly before it's about to turn off, so that's your cue.


Spectral Analysis










All light that we see as white is actually made up of several different colors put together. The relative intensities of the different colors in the mix are what determine the tint of the white we see. For example, cool white LED's have a lot of blue, and warm white LED's have more red or yellow. This measurement was done on a home made spectrometer. The plot below the picture is corrected for the spectral sensitivity of the human eye. Note: the peak in the 900nm region doesn't really exist, it's a piece of the second-order spectrum that's showing up here because of the high intensity of the light source. 

Output and Runtime




ANSI FL-1 runtime ratings are the time it takes for a light to fall to 10% of it's original output (counting from 30 seconds after turning the light on). 

The vertical axis of the graphs below represents a relative brightness measurement using a home made light box. The horizontal axis is time in hours:minutes:seconds. Runtimes are stated in hours:minutes:seconds. These graphs may be truncated to show detail.

*Mode Comparison*

Max










Medium










Throwing Distance

ANSI FL-1 standard for stating a light's throwing distance is the distance at which the peak beam intensity (usually at the center of the beam) is 0.25 lux. I calculate throwing distance and candela (lux at 1 meter) by measuring peak beam intensity at five different distances and using the formula lux*distance^2=constant.


*Peak Beam Intensity: 4532cd*
*Throw Distance: 135*

(As a side note, Nitecore's claims are only 32cd off from what I measured, which is an impressive 0.7% error :thumbsup: )

Subjective Review

Quick break down:

+ Multi color option
+ Infinitely variable
+ AA extender included
+ High max brightness
+ Low min brightness
+ Very good regulation
+ Magnetic control ring
+ Indentations for modes
+ Perfect size for larger hands
+ Firm, screw-on clip

- A bit larger than some might EDC

I'll start by saying this light has replaced the SWM V11 as my new general purpose EDC, a position that was previously held by the SWM V10. This is a hard spot to get into, but the SRT3 has been nothing short of excellent.

My favorite aspect of this light has been the implementation of the magnetic control ring. So far, I've found the magnetic control ring to be the most practical and useful sort of user interface on a multi-mode flashlight for most uses. There are certainly a few uses where a standard switch is preferable, but for general use the magnetic control ring is incredibly intuitive and simple. For my mind at least, it helps to associate the modes with some physical position, instead of just some electronic setting--I know "where the mode is", not just a pattern of switching I have to follow to make it happen. On the SRT3 in particular, the magnetic control ring has been used very effectively. Each mode has it's own position on the control ring, and detents give some satisfying feedback to let you know when it's in the spot for the next mode and help to keep it from sliding out of that position accidentally. The infinitely variable portion of the ring has a detent at the max and min position, but a smooth travel over the intermediate settings so you can get the level you want. The max brightness is about 200 lumens for a AA, and up to around 650 when you use lithium ion batteries, and I've found even 200 lumens is plenty for most short to mid-range tasks in the dark. The minimum brightness is very low--lower than my SWM V10's or V11's, but not quite as low as my EYE10 TIC (which literally fades away into imperceptibility). I find the min is plenty low for reading something without destroying night vision or navigating a dark house without disturbing sleepers.

So far, I haven't found too much use for the red and blue modes other than to entertain my children, but for me that is a significant thing. I know that many people say the red and blue have certain tasks they are especially useful for in low light conditions, but I haven't had the opportunity to use them it those ways, so I won't comment on it at this point.

Taking a look at the output graphs above, you can see that the SRT3 has very good regulation, which is not really the norm for infinitely variable lights. Something about the electronics required for infinitely variable output seem to make regulation of that output harder, but Nitecore has done a good job here of combatting that effect. Also, you can see the regulation holds pretty well for both NiMH and Li-Ion batteries, which is uncommon.

I also want to point out the clip on this light. Many lights this size have a clip, but few of them make me feel confident that the light is secure in my pocket. This clip is held down by two screws, so it's not just a clip-on-clip that will fall off easily. It's also made of a metal that gives a firm hold without being too difficult to manipulate. This seems like a little thing, but it can make a big difference. 

It's also worth noting that the AA extender is included with the light, so you don't have to buy a separate accessory. This is a nice touch, and adds a great deal of functionality. With some extenders I've used there can be trouble with the electrical connection when the extender is in place, but I haven't experienced that here.

The one possible drawback here is the size. The SRT3 is significantly larger than other lights in the single AA or single 16340 classes. It's got an excuse, with the magnetic control ring plus electronics for control of multiple emitters, but this still may be an issue for some. I find it has no trouble settling comfortably into my pocket, and the size is actually just right for my larger-than-average hands, but I can see for some people that it might be a bit larger than ideal.

So, the SRT3 is an all-together excellent general purpose light. I would not hesitate to recommend it to anyone looking for a EDCable single cell light. The magnetic control ring ensures that the multiple modes are not confusing or annoying but only very useful, the construction is on-par with Nitecore high quality, and the large size for its class is not any real hindrance to its use.


*Long Term Impressions*
I'll fill this part in after carrying the light for a while. If nothing get's added here, either I find nothing else worth noting about the light, or I end up not using it often.


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## Bigmac_79 (Oct 30, 2013)

A side note on the layout of the review: if you've been reading my reviews for a while, you'll notice the format is changed slightly. The image hosting site I used to use is closing down, so I've transitioned to a new one that is a bit more restrictive on the number of files I can host there, and is also just less convenient. As a result I've shifted much of the information that used to be in pictures to the video, so the video is longer and the pictures are less. The thumbnails are also smaller than before, but you can still click on them to see the full size image.


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## y260 (Oct 30, 2013)

Nice review! That's an interesting find that a 14500 produces higher lumens that any of the MFG rec'd batteries. I wonder if there any downsides to using the SRT3 with a 14500.


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## Bigmac_79 (Oct 30, 2013)

y260 said:


> Nice review! That's an interesting find that a 14500 produces higher lumens that any of the MFG rec'd batteries. I wonder if there any downsides to using the SRT3 with a 14500.



I doubt there are going to be any significant problems using a 14500, other than possibly decreasing your LED lifetime from 50,000 hrs to 49,500 hrs . I've found this to be pretty reliable, that 14500 batteries will outperform 16340 batteries with the same ratings from the same manufacturer, even for the best manufacturers (for example, the numbers in my reviews are from AW 14500 and 16340 cells). Not sure why this is, but it's one of the reasons I like that the SRT3 comes with the AA extender.


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## phantom23 (Oct 30, 2013)

y260 said:


> I wonder if there any downsides to using the SRT3 with a 14500.


It's ~15mm longer.


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## Bigmac_79 (Oct 30, 2013)

phantom23 said:


> It's ~15mm longer.



Ha, yeah I guess you're right! For me though, that's not really a downside, as I've got large hands, so it feels more comfortable for me to hold when it's a bit longer.


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## demoteamone (Nov 4, 2013)

Thanks for the nice Review Bigmac. I was wondering if notice any jiggling, play when you use the AA battery..... compared with the CR123? Thanks a lots.


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## Bigmac_79 (Nov 4, 2013)

demoteamone said:


> Thanks for the nice Review Bigmac. I was wondering if notice any jiggling, play when you use the AA battery..... compared with the CR123? Thanks a lots.



Nope, no AA jiggling. The extender has a smaller diameter than the rest of the battery tube, so it holds the battery firmly. :thumbsup:






(click on these to see a bigger version)


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## Disciple (Nov 8, 2013)

Will an 18350 fit in this light?


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## Sofastreamer (Nov 21, 2013)

what battery did you measure the 135 m throw distance with?


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## Overclocker (Nov 21, 2013)

Bigmac_79 said:


> Ha, yeah I guess you're right! For me though, that's not really a downside, as I've got large hands, so it feels more comfortable for me to hold when it's a bit longer.





it IS a downside. it ends up being almost as big as 18650 lights but with a puny 14500 power cell inside

it is simply not size-efficient. in my book that sucks


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## Overclocker (Nov 21, 2013)

Bigmac_79 said:


> I doubt there are going to be any significant problems using a 14500, other than possibly decreasing your LED lifetime from 50,000 hrs to 49,500 hrs . I've found this to be pretty reliable, that 14500 batteries will outperform 16340 batteries with the same ratings from the same manufacturer, even for the best manufacturers (for example, the numbers in my reviews are from AW 14500 and 16340 cells). Not sure why this is, but it's one of the reasons I like that the SRT3 comes with the AA extender.




yes 14500 is superior to 16340. particularly the sanyo UR14500 840mah 

though your AW's are most likely using chinese cells


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## Bigmac_79 (Nov 21, 2013)

Sofastreamer said:


> what battery did you measure the 135 m throw distance with?



That would be with an AW 14500.


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## Bigmac_79 (Nov 21, 2013)

Overclocker said:


> it IS a downside. it ends up being almost as big as 18650 lights but with a puny 14500 power cell inside
> 
> it is simply not size-efficient. in my book that sucks



Of course, it's certainly a matter of opinion. If what you need is the smallest possible light for that battery size, there are definitely ultra-compact lights without the extra features of the SRT3. :thumbsup:


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## Colinsdad (Nov 22, 2013)

All I gotta say I purchased one and absolutely love it, especially seeing as how I need a reliable tactical light for use with a CCW. However the one glaring omission I see this light, is the fact that they don't include an Allen wrench with the accessory package. At first I thought it was just an oversight by nightcore by forgetting to put one in the packaging. I contacted nightcore and asked if they could send an Allen wrench and was rebuffed and actually quite rudely which I thought was interesting. So since the allen screws are backing out of the clip on this flashlight, does anyone know the size allen wrench I need to track down to retorque these ? I'm also thinking of a little bit of thread lock may not be a bad idea.


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## Bigmac_79 (Nov 22, 2013)

Colinsdad said:


> All I gotta say I purchased one and absolutely love it, especially seeing as how I need a reliable tactical light for use with a CCW. However the one glaring omission I see this light, is the fact that they don't include an Allen wrench with the accessory package. At first I thought it was just an oversight by nightcore by forgetting to put one in the packaging. I contacted nightcore and asked if they could send an Allen wrench and was rebuffed and actually quite rudely which I thought was interesting. So since the allen screws are backing out of the clip on this flashlight, does anyone know the size allen wrench I need to track down to retorque these ? I'm also thinking of a little bit of thread lock may not be a bad idea.



I don't have the light on me now so I can't check the size of wrench needed, but you should just be able to go to the hardware store and pick up a pack of 'em for pretty cheap. They're good to have around anyway, and besides I don't think they're commonly sold just as a single wrench. They do come in both US and metric sizes, so it's useful to have a set that includes both.


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## Colinsdad (Nov 22, 2013)

BigMac, I have a plethora of Allen wrenches, and this one is tiny! The smaller I have is a 3 mm, and it's huge. I'm going to Harbor Freight to see what I can locate


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## slab288 (Nov 22, 2013)

Just a couple of thoughts.........I don't think it's a downside being 15mm longer it just gives you choice which is always a good thing I recon. And to Colinsdad I wouldn't use thread lock but rather plumbers tape (PTFE) a couple or rounds of that will do nicely and not lock the threads and thereby risk damaging the threads should you ever have to remove the screws again. And my set of allen keys goes down to half a millimetre so if anyone wants to send me their SRT3 I'll be sure to let you know what size it is :thumbsup: slab288


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## Colinsdad (Nov 22, 2013)

Slab, I have PTFE and light duty thread lock.... I'll see what works better


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## Aperture (Dec 31, 2013)

Bigmac_79 said:


> The extender has a smaller diameter than the rest of the battery tube, so it holds the battery firmly. :thumbsup:
> 
> 
> 
> ...


It looks like the extender can be drilled out to facilitate a CR123A/16340 plus 15mm spacer setup, can you please verify this?

I rather take out a spacer to switch to AA than add an extender in case of an emergency.

And many thanks for the great review, keep up the good work.


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## Bigmac_79 (Dec 31, 2013)

Aperture said:


> It looks like the extender can be drilled out to facilitate a CR123A/16340 plus 15mm spacer setup, can you please verify this?
> 
> I rather take out a spacer to switch to AA than add an extender in case of an emergency.
> 
> And many thanks for the great review, keep up the good work.



I can't confirm whether or not that would work, I don't have the equipment or skills to try it, but there does appear to be enough extra material there. My guess would be that you could drill out the extra couple of mm diameter and still have plenty of material there to keep it structurally sound. Because of the way the reverse-polarity design is set up in the head, you might find you need something around the sides of your AA to keep it held in the center to make a solid connection, but it's hard to say without trying it.


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## Aperture (Jan 1, 2014)

Bigmac_79 said:


> I can't confirm whether or not that would work, I don't have the equipment or skills to try it, but there does appear to be enough extra material there. My guess would be that you could drill out the extra couple of mm diameter and still have plenty of material there to keep it structurally sound. Because of the way the reverse-polarity design is set up in the head, you might find you need something around the sides of your AA to keep it held in the center to make a solid connection, but it's hard to say without trying it.



Thanks, really appreciated.


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## boanerges (Apr 3, 2014)

Been thinking on this light for a while. I like the diversity of using CR123's or AA's, and the extra features this light come with! In my mind this is a no-brainer and a definite purchase down the road! Thanks for the review!


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## Danielsan (Apr 23, 2014)

Is there any other XML2 light like this one with a magnet ring that uses CR123 ?


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## InfinitusEquitas (Apr 23, 2014)

Danielsan said:


> Is there any other XML2 light like this one with a magnet ring that uses CR123 ?



Sunwayman V11R. You can also buy an extension to use 14500 batteries. Not sure if it will run off of AA's but probably will at low level.


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## sirshanksalot (May 15, 2014)

boanerges said:


> Been thinking on this light for a while. I like the diversity of using CR123's or AA's, and the extra features this light come with! In my mind this is a no-brainer and a definite purchase down the road! Thanks for the review!



Likewise on all the pluses. The size is the only detractor for me. Still tossing up between this and replacing my lost Eagletac D25C Ti, loved that little light. Made the mistake of backstepping to the Foursevens Mini123 which was a good little light too but the twisty mechanism failed in less than a year and even with replacement on the way doesn't give me tremendous confidence in it's longevity.

I'll likely end up with the older brother of this, the SRT7, for my backpack light.


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## InfinitusEquitas (May 15, 2014)

The D25C is tiny by comparison.


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## ghosty (Feb 6, 2015)

I have been looking around but didn't find answer, hope someone can answer or point me to the answer.

On the Srt3 (or other Srt model), is the control ring self serviceable? If I have sand/pocket lint/dirt trap inside and become gritty. Can I take it out, clean and re-lub it?

I have seen information on the Sunwayman V11R control ring fix, but not Nitecore Srt3.


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## zs&tas (Feb 9, 2015)

The ring effectively floats around the body, I find if a wash in the sink with washing up liquid dosnt do I get a light lube with a straw and blast around the ring usually moves anything. Other than that the heads are probally glued and u may need courage and a vice to get the ring off. Thats probally not really needed though !


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## Guy1017 (Feb 9, 2015)

I really appreciate the review. Putting this on my short list.


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## seantik (Dec 13, 2016)

Very nice review - many thanks. You inspired me and I will really consider buying this light.

Has anyone done some measurements on how many lumen the lowest white light is? Nitecore states that it is 0.1 lumen but how low is it actually?

I looking for a really low light and are pretty hot on a Zebralight sc600 II or III. On the other hand I like the nitecore design and and the option to use red light.

/Seantik


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## ArazelEternal (Feb 23, 2018)

Very nice review. I received my SRT3 tonight and have been playing around with it a bit. I already fell in love with it and the smart ring. Without the extender, I find that it is the perfect size for my pocket and my larger-than-average hands. I cant see myself using the extender right now, but Ill keep it in my laptop bag (it goes with me pretty much everywhere I go for any length of time) where I keep a few other EDC items and always a couple spare batteries just incase it would come down to needing to run AA batteries. I dont see that happening, but cant be too careful sometimes.


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## CelticCross74 (Jul 6, 2018)

years later and the SRT line needs an XHP IP68 overhaul badly. The SRT3 platform is actually VERY good. Just need to tighten things up to IP68 standards, pot the electronics, redesign the reflector etc. I dig it.


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## eurypylus (Jul 26, 2018)

As a seaman working on the bridge, I can't find better replacement for this light.
Rechargeable batteries, with AA batteries adapter in case of emergency, clicky switch with preset setting.
The red light works good shining log book at night, and the brightest setting is good enough to see debris on the side of the ship.

I've use illuminating paint red for red light and green for the brightest setting. How I wish if I can use tritium tube on the ring :-\

Issue is it keep getting kept being "taken away without permission and not return". I hate to use the word "stolen" on ship that I knew everyone so well, but then its the fourth SRT3 I've purchase so far. .._>_<...


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