Convoy S2+ UV Flashlight

[JCDowdy]

Last May I ordered a Convoy S2+ 365nm Nichia UV Waterproof LED Flashlight for the princely sum of $20.04 including shipping.

 

I had discovered a website called the BudgetLightForum.com which is populated by folks who are deep into the hobby of collecting, building and modifying low cost flashlights. I was trying to learn more about how to build an LED flashlight with the intent to install a nice Nichia LED into some suitable body. These flashlight enthusiasts had already discovered the Convoy S2+ UV and were reporting very good impressions of both it's build and performance.

 

For the price it had to be worth a try and I purchased one from GearBest.com as linked above. It took quite a while to arrive, ordered 11May2016 and received about a month later from the other side of the planet.

 

It takes a single 18650 Li battery, which I had already for some regular flashlights. I get them from LIION Wholesale for very affordable prices.

 

When I first turned this flashlight on I was simply dazzled, both literally and figuratively, by the output. In my cluttered home office, with the lights on and sunlight streaming through the window, I was seeing very intense fluorescence from printer paper, mailing labels and everything else in the room fluoresced 14 feet across the room and carpet lint down the hall!

 

As some of you already know I am a partner in a small testing lab which provides spectral analysis and photobiological risk assessment among other things. In the past I posted a spectral analysis of a Black-Ray source kindly provided by Damon, one of our members.

 

Today I am finally presenting my testing of the Convoy S2+ UV.

I must apologize for not sharing this sooner and thank member Enrico for motivating me to action lest he preempt me ;) !

 

Member Cadimum previously provided us with a nice comparison of 365nm torches using a Solarmeter SM 5.0 UV meter.

I have excerpted a copy of one of his attachments below for ease of direct comparison.

- From Cadimum Three 365nm UV torches compared

 

Here is the result for the Convoy S2+ 365nm using my Solarmeter 5.0.

 

 

As you can see I had to back off to a distance of ~15cm to keep from overloading my Solarmeter 5.0 meter. This is a considerable distance compared to Cadimum's test even though we are using the same model meter. Unfortunately I do not own an MTE flashlight to directly compare using my meter. I seem to recall Cadimum or perhaps someone else mentioning somewhere that the MTE beam was slightly dimmer in the center.

 

I mentioned the torch I am showing here in Cadimum's previously cited thread. It visually appears to be a Nichia NCSU276A U365 which is rated at 780mW. This LED has a clear domed lens directly on the chip, unlike the LEDs shown in Cadimum's test. Consequently the Convoy S2+ has a bright central focus as shown on this photo of the beam at about the same distance.

 

 

I subsequently measured the Convoy S2+ 365nm with an OL-756 UV/Vis spectroradiometer.

This is a scanning double monochromator with stray light rejection of ~10^-8, configured for 2nm bandpass using an integrating sphere with a 20mm entrance aperture, scanning at 1nm increments.

 

I had to back off even further, 50cm, to keep the spectroradiometer from overloading!

 

 

Here is a 21June2016 screenshot of the spectradiometric measurements.

 

 

The uppermost spectrum is the Convoy S2+ at 50cm. The value tree on the left shows some of the spectral parameters for this scan. As you can see the peak is not exactly 365nm but was ~4nm higher at 369nm. The spectroradiometer wavelength offset is calibrated to <0.2nm against a mercury line so this is real although only measured at a 1nm interval.

 

The other plots are some lab filters I simply laid over the entrance aperture of the integrating sphere.

In descending order of intensity these are: (edited for readability)

a. 2mm UG11

b. 2mm UG11 / 3mm BG38 stack, and

c. 2mm UG11 / 3mm BG18 stack

 

You can see how the filters attenuate the emission spilling over into the short wavelength visible range which is desirable for UVIVF photography. I did order some of the 20.5mm diameter ZWB2 filters (along with 3 more torches B)) from the Convoy manufacturers web store on Aliexpress but I have not installed them yet.

 

To confirm the peak wavelength observed with the scanning spectroradiometer I checked the unfiltered flashlight using an Ocean Optics USB2000 spectrometer fitted with a CC-3-DA cosine corrected Spectralon diffuser input. A screenshot from the OOIBase32 software is shown below.

 

This fixed single grating diode array spectrometer found the peak wavelength at 368.75nm conforming the peak for this LED is slightly longer than 365nm. I did not note the actual distance for this measurement but the flashlight was positioned such that it was only barely beyond the distance that overloaded the USB2000.

 

I would like to point out that this was done with an older version of the Ocean Optics software which permits the display of a log scale y-axis and so serves as a good comparison of the difference in the dynamic range compared to the scanning double monochromator.

 

I know this is rather long post, but I hope y'all find it interesting.

 

Now that spring is approaching must get out and take some photos!

 

Don't forget your protective eyeware!

[enricosavazzi]

These tests are encouraging. We may indeed have a low-cost alternative to the MTE models. Several of the tests I have in mind are different from these, so there is plenty of room left for more.

 

The MTE 301 has a central diffuse hotspot qualitatively similar to the Convoy, not a ring-shaped one. The MTE uses a different, probably more expensive LED chip carrier (ceramic tub with flat glass window), so the geometry of the irradiated field may be somewhat different.

[Guest]

I wonder whether the Convoy's reading of 191.7, versus the MTE's 97.1, is simply because the hotspot of the Convoy is tighter, thus its output may give a higher reading simply because its output is more concentrated in that hotspot?

 

I have a fused silica quartz diffuser on my MTE, and that appreciably decreases the intensity of its output (as expected). So I also wonder, if the Convoy's output were diffused to the same degree would then the intensity be equivalent?

 

In other words, do they both have comparable output - just in a different pattern/concentration?

[JCDowdy]

Yes it seems encouraging and I am eager to see your tests, Enrico. However, confirming results is very important so we should also attempt to replicate each other's results. I do not recall you saying which meter you have obtained. I hope it is a Solarmeter 5 because that would function as a common reference point that other members also have.

 

The comments on the MTE beam geometry are consistent with those shown by Cadimum which I have just reviewed. I am now not certain how to interpret the meter comparisons with the flashlights in contact with the meters, although it does appear those sources have been filtered whereas mine was not. Differences in beam profile will certainly have an impact on measurement geometry and should always be characterized as part of such measurements.

 

The consensus of opinion seems to be that the MTE 301 had the Nichia NCSU033B and that the MTE 303 has the more powerful NVSU233A U365. The Nichia website rates the optical power of the NCSU033B at 450mW and the NVSU233A U365 at 1030mW. My visual examination, as well as the GearBest site, identifies the LED in the Convoy as the 780mW Nichia NCSU276A U365.

 

Notably, among these 3 LEDs only the NCSU276A in the Convoy has an integral dome lens which obviously must effect the beam profile. I have seen mention on the flashlight enthusiast websites of the de-doming of LEDs to enhance beam uniformity.

 

Certainly one should consider the application of the UV flashlight in regard to optimum beam profile. For use as a focusing aid in the field, I think a brighter hot spot might be preferred. However, for use in excitation of UVIVF macro photography a broad homogeneous beam would seem optimal.

[Cadmium]

John, Very well done tests, and really cool lab and equipment!

The beams are always a problem to measure.

I have been thinking lately of measuring the LED directly, by removing the entire front of the torch, so that only the LED is showing, no reflector, and no shroud, like this:

http://www.ultraviol...&attach_id=8362

 

I have not tried that yet, and I don't know how well that would work out to be the same with other torches.

I have also wanted to try that for a more diffused even light.

I will get one of the Convoy torches and compare.

[JCDowdy]

Thanks Steve, I thought you would find this interesting.

 

I am hoping you can detail for us a bit more on the meter readings of the unfiltered MTE flashlights at standoff distance from the Solarmeter.

 

Measuring the LED directly will definitely reveal the "raw" distribution profile of the emitter. I think at this angle info is sometimes available in the technical documents, see pdf files on associated with each LED.

 

 

How this is redistributed by the reflector is another question. I recall that the Budget Light Forum had discussed a zoomable UV Convoy that is no longer sold. That body, BD04, is however still offered in a white light version. I have some zoomable white light LED flashlights which do not have reflectors but rather lenses that slide to various distances from the LED. Given that 365nm should pass most glass, finding a zoomer that could accept the UV LED chip might be quite versatile. The person that makes them is named Simon and the Budget Light Forum members think highly of him. Perhaps UVP might ask for another production run of the UV BD04.

[Andrea B.]

John, thank you so much for this comprehensive review of the Convoy S2+UV Waterproof LED Flashlight (torch). Such an excellent review will be very helpful to our members and readers. I will be linking to this topic in the Sticky.

[enricosavazzi]

I do not recall you saying which meter you have obtained. I hope it is a Solarmeter 5 because that would function as a common reference point that other members also have.

Unfortunately not, it is a Tenmars TM-213, see http://tenmars.com/webls-en-us/TM-213.html . I have not received it yet, so I don't know how well it will work in practice. My choice was based mostly on the availability of zero (I assume this subtracts the dark current if used while covering the sensor, or any environmental radiation if used with the UV source off) and hold functions, which should be handy. I was also looking for a meter without its sensor attached on-end, so that the sensor will be closer to the illuminated target surface when placing the meter onto the target (e.g. to make measurements at different points in the illuminated field). This is desirable when the radiation source is close to the target. A reasonably low price was also a requirement, of course.

[Cadmium]

John, I have ordered the Convoy, and when I get it I will try to duplicate your setup, and see what readings I get, then try to compare using the MTE in the same setup.

[JCDowdy]

Andrea,

You are most welcome! UVP has been a great help to me so I am glad to contribute in a way that I am able.

 

Enrico,

Interesting meter, I never heard of that brand. A detachable corded detector can be very handy, I have a couple of IL-1400 radiometers with a bunch of different detectors which are used regularly to map output fields of various sources. Nice to keep your hands out of the beam sometimes! One thing I notice about your radiometer is it has a large input optic, so be sure you overfill that diffuser or your readings will have geometric error. Radiometers in general are often highly directional, sometimes intentionally, and alignment to beam axis can be critical. Your detector appears to have a domed cosine corrected diffuser and should be less prone to alignment problems.

 

Steve,

That should give us a nice comparison, looking forward to seeing your results. The setup is simple but let me know if you need any more detail on what I did.

[nfoto]

Rats. Very expensive to get it here to Norway. A total of no less than $ 22.17. Ugh.

 

For that price, I have no problem being patient and wait it out. Spring is a long time ahead in the future anyway.

[Alaun]

Thanks John for all the infos on this little sun!

 

Just got my copy and run my simple comparison with the two MTEs: Just shine the beam on to a white bed sheet from a couple of meters. The whiters (from washing) will transform all (probably only mostly all) the UV into visible light and you can judge the light distribution as well as the power quite well, and it seems to me the little toy outperforms the other two in both respects, more uniform distribution and brighter. (sorry, no pictures taken).

 

Werner

[JCDowdy]

You're welcome Werner, I am looking forward to comparisons from those of you who also own MTEs.

[Cadmium]

I have to say, I am a little disappointed with that seller. I can't find a way to track it, I can't get logged into their site, and when I tell it I forgot my password (which I didn't) it never sends me anything, even to my junk folder.

So, wait and see I guess... but they seem to have a pretty poor system.

[JCDowdy]

Steve, which site did you order from GearBest or Aliexpress?

Shipping was several weeks from both and I did not get much communication from Aliexpress.

[Cadmium]

Thanks John, I will try to calm down :-) GearBest, I finally got on their site, it was crazy. I ordered it on 2/16, so about two weeks so far.

They even have a photo of the packing envelope with my address on it, sitting on their shipping scale, at their site.

[Cadmium]

John, I got the Convoy today. The LED does look like the NCSU276A, but the one I have doesn't' seem to have a rounded dome shaped top, it looks flat to me.

It looks a little brighter, but may be just the dispersion. I still need to test it more.

Off hand, one thing that isn't as good is the lens is hard to replace, it would require removing the LED package from the read of the LED housing, the clear lens doesn't come out from the front.

I have not tried dissembling all of that yet. It looks a little involved, more than with removing the MTE lens.

There are no front threads, so nothing can be screwed on the front, like an adapter ring.

It is small and compact.

More later.

[enricosavazzi]

My test is now available at http://savazzi.net/photography/cheap365nm.html .

 

If you want the bottom line, skip to the end of the page linked above.

 

Edit: something went wrong with the current measurements. The published values are meaningless. I will repeat the measurements and correct the page after recharging the batteries.

[Cadmium]

It is not as involved to take the convoy lens out as I had first imagined.

1) Just unscrew the front end, then use some long pointed scissors or appropriate spanner wrench to unscrew the brass LED housing.

2) The silver reflector and clear front glass lens will drop out easy once the brass LED housing is removed.

It is not much harder than removing the MTE lens, if you have the scissors or spanner that fit.

By the way, once I took the LED housing out, I could see it is 'dome shaped' (photo #3). So it does use the Nichia NCSU276A LED, seen on this Nichia page link (about half way down):

http://www.nichia.co.jp/en/product/uvled.html

Convoy S2+ clear lens = 20.3mm to 20.6mm tolerance x 1.6mm thick (could be 2mm easy).

Here are some pics to show you the parts:

 

[Cadmium]

In my opinion, these two torches produce just about the same amount of light.

The difference between these two torches seems to be their reflectors.

Because the Convoy has a more even beam, and for the price difference, there doesn't seem to be much reason to get the MTE instead of the Convoy.

There are possibly two reasons to get the MTE:

1) If you remove the front ring and glass, you can screw a step up ring into the front of the MTE, for larger filter sizes, if you don't have a dedicated U-glass for the MTE (dedicated glass saves space).

2) It is quicker and easier, and requires no tools in the field to remove/replace the glass with the MTE, especially if you are doing it more often.

 

The MTE 303 has a brighter center, and the Convoy has a more uniform beam.

These are a bit hard to measure and compare for that reason, with the difference in reflectors,

so I am testing using the LED alone, without the reflector.

The LED of the convoy is about 12.5mm deep inside the torch (with the reflector and glass removed), the LED of the MTE it is right on the end (with everything removed),

so I have compensated the MTE with a ring of tape to make the depth and diameter of the light exit the same as the Convoy.

 

Here is a beam test using the LED's with the reflectors removed. I don't see any difference in these two beans, shape or intensity:

 

Here is a meter test. There doesn't seem to be any real difference between the amount of light being produced by either torch/LED.

[Andy Perrin]

Huh, that seems in direct contradiction to JCDowdy's results? Maybe people were getting defective torches that were operating outside the specs, and you got a corrected one that is operating IN the specs, Cadmium?

 

Edit for later readers: I meant Enrico's results, not JCDowdy's here. But I was totally confused between the torches at this point anyway. ;-)

[Cadmium]

It doesn't contradict John's results at all. It is a different animal, and measuring the beam difference is a problem.

These LED's seem to put out the same amount of light, just a different beam.

[Andy Perrin]

I don't understand how you can say that. His graph seems to show that the total power output (Watts in UV) is larger, not just the intensity (Watts/(solid angle*m^2)). See this graph?

 

The blue clearly has more area under the curve. That's not just a question of how the light is distributed.

 

EDIT: pardon, I meant enricosavazzi's results. I think I got confused going back and forth between windows.

[Cadmium]

Andy, I was talking about John's results, not Enrico's.

NOTE: Enrico's comparison uses an MTE 301 torch which is about 2/3rds the strength of an MTE 303 torch (from my comparisons of those two),

and I am comparing the Convoy to an MTE 303 torch in all of these tests I have shown in this topic.

My opinion is based on my results. I do not think the Convoy is any stronger than the MTE 303, but it does have a more uniform dispersed beam pattern.

 

Here are some more beam shots.

It doesn't show up in these photos, but with the reflectors, to the eye you can clearly see that the MTE has a hot spot in the center which is brighter than any other part of the Convoy beam.

The MTE is what I would call a more center weighted or center focused beam.

 

LED alone about 4" distance.

NOTE: This shot shows the MTE on the right, all other shots bellow show the MTE on the left side.

 

With reflectors, about 6" distance.

 

With reflectors at about 3 feet (exposure A).

 

With reflectors at about 3 feet (exposure B ).

 

With reflectors at about 3 feet (exposure C).

This shot better shows the center hot spot of the MTE.

[Andy Perrin]

Yeah, and I agree that your results DO seem to show they are the same. That's why I wondered if you and enricosavazzi got differently-behaving torches. Like maybe there was something defective about his that made it extra bright.