Ultraviolet - Sun vs Flashlight compared

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AnhTran
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Ultraviolet - Sun vs Flashlight compared

Everytime I play with UV flashlight I feel uncomfortable because of the fear that it might be too dangerous for for eyes and skin, I have done some research about how the intensity of UV flashlight compared to the Sun’s UV but i got no answer. So i decided to test it my self and find the answer.
The UV flashlight being tested is Convoy S2 ,LEUVA33W70RL00 LED ,7135*5, zwb2 filter installed.
The Sun being tested is Melbourne’s autumn Sun, at around 2pm, clear sky.

Test 1: Light goes direct to the light meter sensor through a zwb2 filter to filter out visible light.


Test 1 result:

Sun: 472 Lux
.
.
.

Convoy UV hotspot at ~1m: 648 lux
.
.
.

Test 2: Light goes through zwb2, the UV light up the fluorescent powder, the light emitted from fluorescent powder is mearsured.
Reason for test 2: I thought that the zwb2 filter might allow some other wavelengths other than 365nm such as deep red or infrared to go through. This will overestimate the amount of UV in sunlight. So i did a second test, measured the the UV indirectly through fluorescent powder with the intention that wavelength longer than UV will be absorbed by fluorescent powder rather than be converted into another wavelength.





The fluorescent powder is placed at the bottom of the cup, light goes through one hole with zwb2 filter, the emitted light from fluorescent powder will be measured from another hole.
Test 2 result:


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.
.

Conclusion
1. The intensity of UV from the UV flashlight (hotspot at 1m) is roughly equal to UV from the sun.
2. Indirect UV such as UV reflected from wall is negligible, zero lux measured my method used in test 1, about 30cm away, so it seems to be safe playing UV flashlight around house, BUT wear your protective glasses, because you usually play with UV in the dark, when your eyes’ aperture is wide open, so your retina will received a lot of reflected UV.

Test limitations:
- The sun light might be much more dangerous because it contains shorter UV wavelengths which are filtered out by zwb2 filter and was not reflected in the measurement.
-Similar, the UV flashlight might be much worse than the sun UV because it might *contain shorter wavelengths which *might not be filtered out by zwb2 filter and these shorter wavelengths cannot be measured by the lightmeter, therefore the dangerous level was not reflected in the measurements.

I hope anyone with knowledge can help me with the limitations above and point out other defects in my tests. Now i feel comfortable play with my UV light.

Edited by: AnhTran on 05/07/2019 - 11:47
M3CSL
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Thank you for this test, it is very interesting.

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firedome
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Thanks for the test, very interesting. However I am afraid that it is not a true test to the real damage that a UV flashlight can do. Think that the eyes (pupil) will react differently to the outdoor sunlight, and to a flashlight that emits in a narrow spectrum used indoor.

“We can easily forgive a child who is afraid of the dark; the real tragedy of life is when men are afraid of the light.

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Nice set of tests. I can think of a couple of shortcomings but they may not alter the outcome in the end.

Although the amount of UV from the sun may be comparable to the UV from the flashlight at a short distance, people are not usually looking straight into the sun so what your eyes experience is mostly reflected UV (which can still be a lot). And as you already pointed out, the pupil of your eyes are fully contracted in the sun, while fully open when watching the flashlight in the dark, allowing 36 times more light into the eyes.

So yes, wear glasses. Because I can feel UV light as pain in my retina, I can confirm that while the amount of UV from the source may be equivalent, the way people behave and how your eyes work, a high power 365nm UV flashlight, like the UV S2+, does allow much more UV into the eyes than the sun.

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The observation of djozz is very important. Because of the amount of visible light outside, your pupils will contract and therefore limit not only the quantity of visible light but also the quantity of invisible light, like 365nm UV light. Indoors your pupils will be more dilated, and because your pupils will not contract with UV light, the UV light will hit your open eyes with full force!

Your conclusion about indirect UV light needs some clarification. To be sure, I have tested this a moment ago. Take your UV light and position yourself in front of a mirror. Then shine your light into the mirror. BUT ONLY AFTER holding a piece of white (printer) paper in front of you, between your eyes and the light and the mirror. You will notice the typical blue-ish glow shining through the paper. That’s UV light, reflected in the mirror! The same warning goes for the glass in windows, and in a more moderate way, for clean shiny kitchen and/or bathroom tiles.
So unless you are able to avoid all these surfaces at home: always wear protective glasses!

You are a flashaholic if you are forced to come out of the closet, to make room for more flashlights.

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I wonder if it would give you a Tan or be useful for skin conditions etc

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i doubt a flashlight has anywhere near the power of the sun…
it just doesn;t make sense

an AA battery? even an 18650, producing maybe 1 watt, through an LED that is what, 10% efficient?

especially reflected off indoor surfaces, most of which probably absorb it anyway

the sun delivers like 100 watts per square foot, of light, to earth, it would take 1000 watts of input power to LEDs, then concentrated in the same 1 square foot..

good experiment though.

i’d have done it too, if i’d thought about it Smile

wle

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Am I correct in thinking Australia may have higher UV from the sun than Europe/USA due to ozone hole? 

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Clever tests and nice report.  Thank you AnhTran.

AnhTran
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It’s very nice to know that my test is interesting to you guys. I stated in my conclusion about the necessary of wearing UV protective glasses but I think I haven’t emphasised it enough. I think your skin is safe ( just don’t point the flashlight directly to you at close range and prolonged, and be aware of highly reflective surface as wle noted)

But please wear your UV protection glasses when using UV flashlight, djozz and Henk did an excellent job in explaining the reason.

I also found that my prescription glasses did quite a good job of filtering out the UV, i will post more test results here

M3CSL
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would regular sunglasses work for UV protection? say, Oakleys or similar?

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Thanks for the very interesting information and knowledge. Beer

AnhTran
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Test with my prescription glasses


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They are probably plastic. This makes them much safer compared to actual glass.

WalkIntoTheLight
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Very interesting test. Actually, I’m somewhat surprised the flashlight is as strong in UV as sunlight. But, I suppose the 5×7135 configuration does produce a fairly strong beam. I still find it hard to believe that reflected UV flashlight light is much of a concern, unless you’re using it a lot.

Even more surprising is this comment:

djozz wrote:
I can feel UV light as pain in my retina

I’m not sure what to make of that. I’ve never heard of such a thing. Closest is the sandpaper-effect that people get on their corneas from being exposed to UV-C. But that’s a real physical effect. UV should be basically invisible. Maybe some skin-burning after prolonged exposure on the retina, but that would be an after-effect.

AnhTran
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WalkIntoTheLight wrote:
Very interesting test. Actually, I’m somewhat surprised the flashlight is as strong in UV as sunlight. But, I suppose the 5×7135 configuration does produce a fairly strong beam. I still find it hard to believe that reflected UV flashlight light is much of a concern, unless you’re using it a lot.

Yes the result from my test is that the intensity is comparable, BUT only in terms of wavelength that is allowed to pass through zwb2 filter.

I think the Sun has much more damaging UV than flashlights because it is not filtered with any filter

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WalkIntoTheLight wrote:
djozz wrote:
I can feel UV light as pain in my retina

I’m not sure what to make of that. I’ve never heard of such a thing. Closest is the sandpaper-effect that people get on their corneas from being exposed to UV-C. But that’s a real physical effect. UV should be basically invisible. Maybe some skin-burning after prolonged exposure on the retina, but that would be an after-effect.

Naw, I “feel” the same thing.

Always thought it was just my imagination, in that playing with my UV lights (shining on walls, floors, etc., to discover any… “leavings”), that I’d get a headachey feeling, or actually an eyeachey feeling, within just a few minutes.

Kinda like “sunlight headache” when you’re outdoors in bright sunlight, surrounded by light-colored sidewalks, walls, etc., and the brightness of the light all around you is just too overwhelming.

After I saw similar comments from people here, I decided it in fact wasn’t my imagination.

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WalkIntoTheLight
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Lightbringer wrote:
WalkIntoTheLight wrote:
djozz wrote:
I can feel UV light as pain in my retina

I’m not sure what to make of that. I’ve never heard of such a thing. Closest is the sandpaper-effect that people get on their corneas from being exposed to UV-C. But that’s a real physical effect. UV should be basically invisible. Maybe some skin-burning after prolonged exposure on the retina, but that would be an after-effect.

Naw, I “feel” the same thing.

Always thought it was just my imagination, in that playing with my UV lights (shining on walls, floors, etc., to discover any… “leavings”), that I’d get a headachey feeling, or actually an eyeachey feeling, within just a few minutes.

Kinda like “sunlight headache” when you’re outdoors in bright sunlight, surrounded by light-colored sidewalks, walls, etc., and the brightness of the light all around you is just too overwhelming.

Are you sure it’s not from the visible violet light that is also emitted from the UV source?

Or, is it possible it’s an imaginary effect? Like people that claim they are sensitive to EMR from cell phones or wifi, but when they are actually given a blinded test, there’s no effect.

I dunno, maybe it is a real thing. I’m just surprised that something invisible could cause an immediate effect of pain. I get that extended exposure might cause pain, perhaps from a “sunburned” retina.

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WalkIntoTheLight wrote:
Are you sure it’s not from the visible violet light that is also emitted from the UV source?

ZWB2 filter, too.

Wasn’t expecting any effect at all, as I’ve still got a few “black lights” (eggplant-purple fluorescent tubes) that never gave me any issues.

Playing with a bare UVLED in a ’501 host, I noticed the “headache” after a few min. Chalked it up to anything but the light. Every time I’d do it, though, same dealy.

S2+ with ZWB2 filter, same dealy. Okay, not a coincidence anymore… Ain’t violet light nor “leakage”, but whatever’s coming from the both the bare UVLED and now with the filter. That pretty much leaves UV.

WalkIntoTheLight wrote:
Or, is it possible it’s an imaginary effect? Like people that claim they are sensitive to EMR from cell phones or wifi, but when they are actually given a blinded test, there’s no effect.

That’s just it, I don’t want to get blinded, so I keep UVing to a minimum.

WalkIntoTheLight wrote:
I dunno, maybe it is a real thing. I’m just surprised that something invisible could cause an immediate effect of pain. I get that extended exposure might cause pain, perhaps from a “sunburned” retina.

Wellp, I’m a bit of a hyperæsthete. Bright lights can give me migraines, loud sounds bother me (even soft sounds when it’s otherwise quiet). I gotta wear a baseball cap at work because the damned overhead fluorescents flicking at me in my peripheral vision will give me headaches/eyeaches by lunchtime.

I joked that I was part Reman, but nobody got it.

Anyway, it doesn’t surprise me that I’d be sensitive to UV.

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Yeah, polycarbonate should filter something like 99%+ of UV. I was considering building a S2+ UV triple until I remembered. I know someone did it with a C8F once, would work much better lol. My other concern was that the Vf of the UV emitters tends to be pretty damn high, and I'd want some sort of compatible buck driver to do it.

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Scallywag wrote:

Am I correct in thinking Australia may have higher UV from the sun than Europe/USA due to ozone hole? 


Dont think so. Various gas layers around earth are more or less consistant.
UV level depends from the angle of sunlight. So all factors like season, distance to the equator and time do matter, but sometimes they may give same angle in different regions.
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With the exception of politicians, most humas only have two eyes. So take good care of them.
I try to do so as good as I can. Nevertheless, there is always that itchy feeling after using a UV flashlight.
Your eyes can’t help it, they just don’t respond (contraction of pupils) very well to UV light.

For those who care, and not just down under, here is something you might wanna read.
Dr. Ruth Westheimer used to say: “Always Wear Protection”. And Jane would add: “Because You’re Worth It.”

You are a flashaholic if you are forced to come out of the closet, to make room for more flashlights.

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Thanks, I was wondering about this too.

  1. Isn’t your meter meant for measuring visible light? Among other things, I think the white dome diffuser on your meter is filtering out UV light.
  2. In natural eyes, very little UV reaches the retina. Our corneas and lenses filter out UV light. That’s why things look funny after cataract surgery.
joechina
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kiriba-ru wrote:
Scallywag wrote:

Am I correct in thinking Australia may have higher UV from the sun than Europe/USA due to ozone hole? 

Dont think so. Various gas layers around earth are more or less consistant. UV level depends from the angle of sunlight. So all factors like season, distance to the equator and time do matter, but sometimes they may give same angle in different regions.

Well, I remember a friend traveling to Australia in Summer. He said without head or long sleeves he got a sunburn within MINUTES.
He is a normal middle European guy with dark hair.
So I do think be very careful with the sun down under.

I also get headache within a minute when I use my UV S2+ light without glasses.

kiriba-ru
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Australian or German summer ? Big Smile

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joechina wrote:
I also get headache within a minute when I use my UV S2+ light without glasses.

Ha! See? So I’m not the only one…

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WalkIntoTheLight
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Lightbringer wrote:
joechina wrote:
I also get headache within a minute when I use my UV S2+ light without glasses.

Ha! See? So I’m not the only one…

I’d still like to see a proper (double-blind) test. Smile

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Oh, great, so you want him and me to go blind…

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Henk4U2
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Lightbringer wrote:
Oh, great, so you want him and me to go blind…

No, a proper test result is the one where 50% of the test persons are hurt beyond repair. Or killed.
So you might get lucky.

You are a flashaholic if you are forced to come out of the closet, to make room for more flashlights.

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WalkIntoTheLight wrote:
Lightbringer wrote:
joechina wrote:
I also get headache within a minute when I use my UV S2+ light without glasses.

Ha! See? So I’m not the only one…

I’d still like to see a proper (double-blind) test. Smile


I have been working with several sources of uv light since I was 21 and the instant painful effect on my retina is real and only with uv light (i.e. not in bright sun). I can not imagine not noticing the light of a uv flashlight entering my eyes.
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I’m not sure I understand the test. Can this luxmeter measure UV? UV is not measured in lux terms but in radiant output (~1800mw for the LG LED ). A special meter is required to measure UV from an LED or from sunlight. Measuring the luminescence of a material can be done by a luxmeter I guess, but is highly dependant on the material being used and the type of UV in the light source. The Convoy outputs UVA from 320nm to 400nm, with a very minor amount to visible light (compared to the amount of UVA). The sun produces UV starting at the MW range (~300nm) up to 400nm, and of course lots of visible light. Anything below ~300nm is blocked by the atmosphere (ozone layer). The MW UV from sunlight is mostly responsible for sunburns. ZWB2 is a UV pass filter with a pretty wide range – lots of MW will get through from the sun (but very little visible).

That “scratchy” feeling you get from UV is caused by wavelengths below 320nm – called “welder’s burn” – keratosis. Basically a sunburn of your cornea. Really bad, wear UV protective goggles. UVA not so bad but still a good idea to wear protection. Some people are more sensitive (can see deeper into the UV spectrum). Most can only see down to 380nm. Older folks with yellowed lenses (before cataract surgery) won’t see very much below 410nm (one reason old ladies have dyed their hair excessively blue). New lenses make a dramatic difference in the blues one sees. Artificial lenses can be selected to filter UV. Some lenses are fluorescent and can be quite problematic for people using UV lights.

Be aware that all protective goggles are not the same. Some will block anything below 400nm (the best) while many pass wavelengths down to 380nm. You can easily see this by putting on the goggles and looking at a Convoy with ZWB2 filter. If you see nothing, the goggles are blocking at 400nm. If you see a dim violet light, the goggles are (hopefully) blocking at 380nm. Shine the light through the goggles to illuminate a luminescent material to be sure they are blocking UVA below 380nm.

Mark

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