# ReviewTheLight: Nitecore P20UV (800 White Lumens + 320mw of 365nm Ultraviolet)



## Bigmac_79 (Aug 7, 2014)

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Nitecore is one of the leading innovators in flashlight tech, consistently among the first to adopt new ideas and designs. In the P20UV, Nitecore adds a white/UV light combo to their dual rear power/mode switches and uses three different interface options to create a very versatile light.



_
Thanks to Nitecore for providing the P20UV for review._

I’ll be reviewing the P20UV 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 P2UV. 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: 75 USD





Product Manual





Dimensions





Plus, here's a few shots with some good detail - Click for full size.












*User Interface*

The P20UV has a three choices of interfaces, with the two rear buttons controlling the output of the single white and four UV emitters. The Power switch is raised higher of the two and is covered with a rubber boot, and the Mode switch is activated by a metal lever system with a low wide pressing area. The modes are Low -> Medium -> High -> UV, but not all modes are available on all interfaces.

To select which of the three interfaces to use: Turn the light off, loosen the head, press and hold the Mode button, re-tighten the head. The light will then flash 1, 2 or 3 times, indicating which interface has been selected. Interface 3 is the default.

The three interfaces of the P20UV are:
1) Tactical: High -> UV
2) Law Enforcement: Medium -> High -> UV
3) General: Low -> Medium -> High -> UV

So, of the four modes available, General has all of them, Law Enforcement has three of them, and Tactical has two of them.

To turn the light on, you can either hold the Power switch about halfway down, and the light will turn on until you release pressure, or you can click it all the way down, and it will stay on until you click it again. Once the light lis on, you cycle through the available modes (determined by which of the three interfaces you selected) by quickly pressing the Mode switch. 

The P20UV also has Nitcore's "Strobe Ready" feature. At any time the Strobe mode is easily accessible: if the light is of, the Strobe mode is activated (momentary on) instantly upon pressing the Mode switch, and will stay on until you release the mode switch. If the light is on, the Strobe mode is activated (constant on) by holding the Mode switch for about half a second, and will stay on until you press the Mode switch again or turn the light off with the Power switch.

Finally, the battery status can be roughly checked by loosening then tightening the tail cap by flashes of a red LED under the power switch. Three flashes indicates a battery charge of >50%, two flashes means <50%, and one flash means the battery is almost dead.

*Action Shots*

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

Light in Hand






MugShot






BeamSlice






White Wall
_ISO 100, f/3.5, 1/20" 
_








*the UV photo was taken as a closer distance and on a white piece of printing paper, instead of the normal wall I use, because the walls of my house do not fluoresce 

Indoor Shots
_ISO 100, f/3.5, 1"
_









Outdoor Shots
_ISO 100, f/3.5, 2.5"
_










*Performance*

Submersion: I submersed the P20UV under a foot of water for about an hour, clicking both switches several times. I found no evidence of water entering or damaging the light.

Heat: The P20UV automatically steps down in output after a few minutes for both High and Medium mode, so there is no chance of overheating unless you repeated re-activate the High mode after stepdown many times.

PWM: The P20UV does use pulse-width modulation on Low and Medium modes, but not on High mode. It is not noticeable to the naked eye, but is detectable by a camera.

Drop: I dropped the P20UV from about a meter onto various surfaces (including grass, carpet, dirt, and hard wood), and found no cosmetic or functional damage.

Reverse Polarity Protection: The P20UV does have built-in reverse polarity protection of a partially mechanical nature, so you will need to use button-top cells in this light. 

Over-Discharge Protection: The P20UV automatically steps down in brightness after three minutes, then steadily decreases in output for the rest of the run, so a dim light is your signal to change the battery. Also, you can use the built-in battery voltage indicator to check the battery status at any time (see the UI section).


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. 

This spectrum of the UV LED's is particularly interesting, and is at the border's of my instrument's detection range. If you look closely you can also see a bit of light in visible range (the red and green band, corresponding to the two bumps near 550 and 600 nm), caused by the slight fluorescence of the plastic in my spectrometer's diffraction grating . As with the white spectrum, there is a second-order spectrum that gives a false reading at longer wavelengths (the right side of the graph), and this can be ignored.

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*

High




Medium 




It's a bit hard to see what's going on in these pictures, but it matches what's explained in the manual. For both High and Medium mode, there is a forced decrease in output after about 3 minutes (to decrease heat and increase battery life), after which the output is unregulated. However, if you desire you can turn the light back to High or Medium output after the drop, you just need to be aware of the heat.


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.






Subjective Review

Quick break down:

+ Bright
+ Surprisingly nice beam
+ Has 365 nm Ultraviolet
+ Different mode sets available
+ Simple UI once you set it
+ "Strobe Ready"
+ Hinge switch is great
+ Little visible light from UV emitters
+ Fun to use

- Not as much UV as their CU6
- UI takes some reading to figure out
- No regulation after 3 minutes

So, I'll start of by saying this light has been a lot of fun to use, but that's not the point of the P20UV. This is my first professional-style ultraviolet light, and it's just that--very professional. The whole setup of the light shows that it's not built to be played with, but instead is for those who need ultraviolet light on a regular basis, and will benefit from having white and ultraviolet light together in the same device.

First, the user interface. It's a bit complicated to work out at first (watch the video above to see me fumbling through it  ), but once you get it set up it's very simple, and the multiple interface options means you'll be able to customize it for your purposes. Personally, I like the "General" interface, which has all output levels available, but I can certainly imagine someone preferring "Tactical" setting, which has only the UV and High (plus Strobe). It is a bit difficult to do the sequence required to change which interface you use, but it's not the sort of thing you're likely to be doing in a high pressure situation, rather you will want to choose the setting you like in advance, then use it when your work begins and not plan on changing it during use. Once you have it set, the Power button will always turn it on/off, and the Mode button will easily change you between the modes. I love the use of the hinge-style switch, and I'd like to see it implemented in a lot more lights (thought no doubt Nitecore intends to keep it to themselves, and I suppose that's probably fair :sigh. It's very easy to use, and I appreciate that the power switch extends further but the mode switch is wide and hard metal, so they can be easily distinguished. Having the switches right next to each other but easily distinguishable means you only need one grip to access both switches, but you're not going to get them mixed up. In addition, it's nice to have the Strobe readily available but not part of the main mode sequence. I've said hundreds of times, if a light is going to have a strobe mode it needs to be easy to access on purpose and very hard to activate by accident. The only thing that I don't like about the Strobe on the P20UV is that the time it takes to activate when the light is already on seems a little bit short, so that if I only want to change the mode I have to remember to press the button and release quickly. It wasn't a huge issue, just something I had to get used to. When the light is off, I do like that the Strobe activates instantly. 

Another thing to note is that the UV mode is present in every setting, so as I said, this is a light for those that are going to need UV on a regular basis. It also does get remembered by the mode memory, so you can set it to be the first thing that happens when you turn the light on. I also really like that the UV is in the 365nm region (as confirmed by my measurements). From what I've seen, 395nm is a more popular choice for many lights. That's fine, but you need to be aware of the best wavelength to use for your desired application, as different materials fluoresce best at different wavelengths. So, if you need 365nm for your application, it can be harder to find a good light for it. Generally, 395nm is on the border of visible, and is probably what most people think of when they envision UV light, as it has that distinctive deep purple look, so if you don't mind that extra visible light then 395nm can work well. However, if you really need fluorescent materials to be quickly distinguishable from their surroundings, that visible light can get in the way. 365nm UV is further out of the visible range, so even the trailing end of the peak is unlikely to be visible, and fluorescent objects will be the only things lit by the light, making them much easier to pick out from their surroundings quickly. The first things that come to mind are looking for UV authentication marks on currency or looking for scorpions, and in both of these cases you want to be able to identify the material quickly. Unfortunately, I've heard many reports of 365nm UV LED's that put out a lot of white visible light in addition to their UV light. I can't find any explanation for this, but my guess is that the material of the lens or of the LED dome itself are fluorescing, giving off the white visible light. This can be a hindrance in those situations where you want little other light to distract you. Fortunately, the P20UV seems to put out very little visible light, though the emitters do have a faint white/purplish look to them [I don't recommend looking at them long, I do recommend reading up on UV eye safety]. You can see the beamshots and the spectrum graph above to see how little visible light is put out. So, the P20UV is going to be good for those cases where you're looking for materials that fluoresce well at 365nm, and you want little visible light from the surroundings.

On the negatives, this light doesn't have as much sheer output as some other UV lights, such as Nitecore's CU6. I don't have a way to measure wattage, but they claim the CU6 has 3000mW, and the P20UV has 320mW. This is believable to me, because the CU6 uses a larger more modern LED for it's UV emitter, and the P20UV uses a set of four lower-output 5mm LEDs. In addition to this, the P20UV emitters don't really get prime position in the reflector, compared to the single large emitter that it's mostly it's own reflector in the CU6, so the P20UV has a much floodier UV beam, which means you'll be using at closer ranges. If you need more UV output and better throw, the CU6 might be worth a look.

The only other negative I found is that after 3 minutes the P20UV drops it's regulation and goes to a lower output. This isn't a huge issue, as if you want you can turn it off and back on to get back to the high output, but it's just not ideal if you want to be picky. It will help keep you from overheating the light or needlessly draining the batteries though, so you decide for yourself if you like that feature.

When it comes to the little things, I have come to expect Nitecore to nail them, and they have with this light. The construction is solid, the threads are smooth, the switches are good quality, the style just looks good, the beam even manages to look pretty good with the four holes in the reflector. These all come together to make the light enjoyable to use. 

In conclusion, the P20UV is a rare light that combines high output white with high energy UV in a very professional manner, giving several options of UI's for various circumstances. If you need UV on a regular basis and plan to use it mostly at close range (I find things within ~20 ft easy to see), the P20UV is going to be among your best options.


*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 (Aug 7, 2014)

Objective portion just needs indoor beamshots and the runtime graphs, then on to the subjective portion :thumbsup:


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## TheThor (Aug 7, 2014)

The first nitecore p20uv review on the forum. Nitework~! Look forward to see the complete review:naughty:


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## Bigmac_79 (Aug 7, 2014)

TheThor said:


> ...Nitework...



I see what you did there, very witty


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## Labrador72 (Aug 8, 2014)

Thanks for the review Bigmac!


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## Bigmac_79 (Aug 8, 2014)

Labrador72 said:


> Thanks for the review Bigmac!



You're welcome!


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## TheVat26 (Aug 9, 2014)

Great job BigMac! So at range, the beam pattern doesn't seem to bad considering the the extra UV's in the reflector. How would you compare the main power switch travel to constant ON, resistance, and responsiveness (does it flash as quick as you depress or is there a slight delay) to the creamy and perfect (to me at least) switch if the Klarus XT11 and XT2C?

How about the beam profile of the predominantly floody beam and slight blue tint of the XT11? 
I'm super curious about the P20 vs XT11 (huge Klarus loyalist here) because the P20 seems a tad more innovative (minus the lack of a SS bezel like the XT11), but have had Nitecore products that had very stiff switches and very blue tints. I kinda have clammy hands and experience a little hand slide trying to turn them on.


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## Bigmac_79 (Aug 9, 2014)

TheVat26 said:


> Great job BigMac! So at range, the beam pattern doesn't seem to bad considering the the extra UV's in the reflector. How would you compare the main power switch travel to constant ON, resistance, and responsiveness (does it flash as quick as you depress or is there a slight delay) to the creamy and perfect (to me at least) switch if the Klarus XT11 and XT2C?
> 
> How about the beam profile of the predominantly floody beam and slight blue tint of the XT11?
> I'm super curious about the P20 vs XT11 (huge Klarus loyalist here) because the P20 seems a tad more innovative (minus the lack of a SS bezel like the XT11), but have had Nitecore products that had very stiff switches and very blue tints. I kinda have clammy hands and experience a little hand slide trying to turn them on.



Hi TheVat26, thanks for your questions! Yes, when you back off from the beam it's really not bad. Unfortunately I can't compare the switch to either of the Klarus lights you mentioned, as I haven't reviewed (and don't own) either of them. The switch on the P20UV isn't really very still, but there is a travel distance of a couple mm before the momentary activation. Once you reach that position however, there is no delay for the light to turn on, due to the use of a mechanical switch (a mechanical switch always activated immediate, where one based on sending an electric signal can have some delay depending on the circuit design). The tint of my P20UV sample seems very good compared to other lights, almost bordering on neutral. If you like you can take a look at the spectrum I took, and compare it to some other lights I've reviewed (for example, the cooler SR52 makes a good contrast), and see that the peak in the red/yellow region is relatively high in the P20UV.


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## johnroq220p16 (Aug 9, 2014)

Hi, I got the original P20 just wonderin' if the main led in the P20 UV is different than the 1st P20. Because I read somewhere stating the P20 UV's led is white...thanks.


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## Bigmac_79 (Aug 9, 2014)

johnroq220p16 said:


> Hi, I got the original P20 just wonderin' if the main led in the P20 UV is different than the 1st P20. Because I read somewhere stating the P20 UV's led is white...thanks.



Yes, the main emitter of the P20UV is white, and the four side emitters are the UV source. I don't have a regular P20, but Nitecore's site states it uses an XM-L2 T6, which is the same as the main emitter of the P20UV.


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## ven (Aug 9, 2014)

Great review as always ,thank you:thumbsup:


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## Bigmac_79 (Aug 9, 2014)

ven said:


> Great review as always ,thank you:thumbsup:



Thanks, glad it was helpful!


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## Bigmac_79 (Aug 13, 2014)

Subjective review posted, review complete 

This has been a fun one :thumbsup:


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## outofdoor (Aug 19, 2014)

Thanks for sharing your review! Can I quote it in somewhere?


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## Norm (Aug 19, 2014)

outofdoor said:


> Thanks for sharing your review! Can I quote it in somewhere?


Perhaps if you mention where. Somewhere doesn't tell us much? - Norm


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## outofdoor (Aug 19, 2014)

Such as Facebook.


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## outofdoor (Aug 19, 2014)

Norm said:


> Perhaps if you mention where. Somewhere doesn't tell us much? - Norm



Such as Facebook.


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## Bigmac_79 (Aug 21, 2014)

I sent you a PM outofdoor.


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## _UPz (Aug 22, 2014)

Thanks for another great review! :thumbsup:


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## Bigmac_79 (Aug 22, 2014)

_UPz said:


> Thanks for another great review! :thumbsup:



Glad it's appreciated  

(Typed by large fingers on a tiny device, please excuse brevity and typos. )


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## TheVisitor (Oct 19, 2014)

Thanks for the review - helped me to decide the torch is for me and purchase. Thanks


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## Bigmac_79 (Oct 19, 2014)

TheVisitor said:


> Thanks for the review - helped me to decide the torch is for me and purchase. Thanks



Glad it was helpful!


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## NoNotAgain (Oct 21, 2014)

Bigmac 79,

How bright would you judge the UV portion of this light to be? I also own the P20UV and am disappointed with the UV brightness. My Led Lenser V2UV using only 3 leds is much brighter than the Nitecore P20UV.

I typically use the UV for finding places that the cat yacked something up and the Nitecore isn't cutting it.


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## y260 (Oct 21, 2014)

NoNotAgain said:


> Bigmac 79,
> 
> How bright would you judge the UV portion of this light to be? I also own the P20UV and am disappointed with the UV brightness. My Led Lenser V2UV using only 3 leds is much brighter than the Nitecore P20UV.
> 
> I typically use the UV for finding places that the cat yacked something up and the Nitecore isn't cutting it.



If your lenser seems much brighter, that could indicate a shift towards the visible spectrum, which may light up more of a room, but isn't "true" UV. I find the P20UV to be moderately powerful and perfect for close-range UV stuffs. Like finding marks on currency or on a passport, etc.


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## Bigmac_79 (Oct 21, 2014)

NoNotAgain said:


> Bigmac 79,
> 
> How bright would you judge the UV portion of this light to be? I also own the P20UV and am disappointed with the UV brightness. My Led Lenser V2UV using only 3 leds is much brighter than the Nitecore P20UV.
> 
> I typically use the UV for finding places that the cat yacked something up and the Nitecore isn't cutting it.



It's hard to say how bright it is, as lumens are really only for visible light. Nitecore claims 320mW for the UV power here, and I have no reason not to believe them. If this isn't enough power, they also have the CU6, which I haven't reviewed, but claims 3000mW.

However, though the power certainly matters, when it comes to using a UV light the actual wavelength of the UV is very important. With visible light you're just bouncing light off stuff so all you need to do to see it better is add more light. With UV, you're trying to get the light absorbed by an object so that it will re-emit light of it's own, and it's that light you see, so what you really need to do is hit the right wavelength. For whatever reasons, most UV lights either claim to be 365nm or 395nm. I haven't done enough research on them to know much about the spread, but you can see the P20UV seems to peak pretty close to 365 as claimed (see spectrum in the review). 365nm UV is further from the visible spectrum, so even if it is a very powerful light, you won't see much of the actual UV light, just mainly the light from the fluorescing objects. 395nm UV is closer to the visible spectrum, so a less powerful light can still appear to be fairly bright. Also, 365nm will generally look more whitish, where 395nm tends to look more like a deep purple. So which is better? It depends on what material you want to see. A while back I found a chart that showed when wavelength various materials reacted best too, but unfortunately I didn't bookmark it. The little presents your cat leaves may fluoresce better at one frequency than the other, so you need to decide which one. Also, because the 365nm light is less visible, it tends to make fluorescing objects stand out in the apparent dimness of the beam.



y260 said:


> If your lenser seems much brighter, that could indicate a shift towards the visible spectrum, which may light up more of a room, but isn't "true" UV. I find the P20UV to be moderately powerful and perfect for close-range UV stuffs. Like finding marks on currency or on a passport, etc.



Yeah, I don't know what the wavelength of your led lenser's UV is, but in general it seems most of led lensers lights are fairly under-powered, so I would guess it's a 395nm, which would explain why it appears brighter.


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## NoNotAgain (Oct 22, 2014)

y260 said:


> If your lenser seems much brighter, that could indicate a shift towards the visible spectrum, which may light up more of a room, but isn't "true" UV. I find the P20UV to be moderately powerful and perfect for close-range UV stuffs. Like finding marks on currency or on a passport, etc.



I'm using the light in almost total darkness. There's a throw comforter on the sofa which strangely has a number of blocks which fluoresce quite brightly.The Nitecore P20UV doesn't light up the comforter like the Led Lenser. The same thing for the lumensiant dial on my watch.

Finding cat yack is much easier after you hear them go than waiting for the morning and then having to scrub the hardwood floor and re-oil.

I've got a lab grade UV / black light, but it's got to be plugged in making it a pain to use.


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## Bigmac_79 (Oct 22, 2014)

NoNotAgain said:


> I'm using the light in almost total darkness. There's a throw comforter on the sofa which strangely has a number of blocks which fluoresce quite brightly.The Nitecore P20UV doesn't light up the comforter like the Led Lenser. The same thing for the lumensiant dial on my watch.
> 
> Finding cat yack is much easier after you hear them go than waiting for the morning and then having to scrub the hardwood floor and re-oil.
> 
> I've got a lab grade UV / black light, but it's got to be plugged in making it a pain to use.



Do you still have the manual or box for your V2UV? I tried to look it up but just found this: http://www.amazon.com/dp/B00097A7NE/?tag=cpf0b6-20. If you have the box or manual it might say the power in mW or the frequency in nm. The two most likely reasons for the V2UV to perform better at those tasks are either that it has a better frequency for those materials, has a higher power output, or both.


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## NoNotAgain (Oct 22, 2014)

I've got the box, but don't recall them having a manual inside. I've checked all three boxes and they're all the same, no manuals.

The only thing I can add is that there is a sticker inside the box indicating Nichia LED's were used. I looked up Nichia UV led's and the only unit matching the packaging is the NSPU510CS. The charts appear to suggest that the led operates between 365-370nm at a power rating of 15.3mw .

The model light number is/was 7732DUV

Coast list the model as PX10, but not information on the UV capabilities.


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## Bigmac_79 (Oct 22, 2014)

NoNotAgain said:


> I've got the box, but don't recall them having a manual inside. I've checked all three boxes and they're all the same, no manuals.
> 
> The only thing I can add is that there is a sticker inside the box indicating Nichia LED's were used. I looked up Nichia UV led's and the only unit matching the packaging is the NSPU510CS. The charts appear to suggest that the led operates between 365-370nm at a power rating of 15.3mw .
> 
> ...



That's interesting, it looks like it's got the same wavelength, and 6 emitters with 15 mW each is only 90 mW. I guess I can't say why your V2UV seems better at finding the cat's stains :shrug:


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## Tenryu137 (Jul 28, 2015)

Hello Bigmac, great review :twothumbs
i'm new to this flashlight world and the only flashlight i owned is a cheap 10 dollar plastic 

Do you think P20UV is a good choice for a newbie like me? I need it for everyday carry and i just got an ESP LHU 14-35 holster from my friend....


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## seong87 (Oct 4, 2015)

Just brought the p20uv.great light but i notice the four uv emitter has 3were white and 1 purple when pointed to the wall at close distance.is that same with the p20uv everybody has purchase?THANKS.


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