# Difference between 365nm and 375nm UV lights?



## techwg (Dec 10, 2014)

Does someone here have both a 365 and a 375 nm wavelength LED flashlights that they could take pictures to show the difference between them? I am not sure how significant the difference is, I mean it is only 10nm difference.


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## archimedes (Dec 10, 2014)

Wavelength change of orange, through yellow, to green light is "only" ~ 30nm.

Beyond ("ultra") violet, light is not "visible". The visible light seen from "365nm" (etc) emitters is mostly of other wavelengths in the spectrum.

If you are referring to fluorescence, it definitely matters which wavelength(s) are used.


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## techwg (Dec 10, 2014)

archimedes said:


> Wavelength change of orange, through yellow, to green light is "only" ~ 30nm.
> 
> Beyond ("ultra") violet, light is not "visible". The visible light seen from "365nm" (etc) emitters is mostly of other wavelengths in the spectrum.
> 
> If you are referring to fluorescence, it definitely matters which wavelength(s) are used.


What I mean, is if people can show an image with a 365nm light on something and then another image with 375nm so that I can compare the visible light production and the luminescence between the two different wavelengths. I have a rubbish little 375 1 AAA light which is on the blink (literally) and have ordered an ultrafire 375, which I thought was lower than my existing one (but I checked my old emails and found the one I already have is also 375). So now I am looking into 365 versions of the same light I am getting but I am trying to find out, empirically through seeing images that hopefully someone can produce here, so that I know if the difference is worth the added and increased expenditure.

The ebay item I have actually ordered is 151423132271 and the one I am sort of looking into *maybe *getting if I am shown the difference is *big* enough, is 150985224675


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## archimedes (Dec 10, 2014)

What are you trying to fluoresce?

Not all things fluoresce at the same wavelength....


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## techwg (Dec 10, 2014)

Nothing specifically. I just have read that the lower the better and the more clear and defined the fluorescence. I found this great link showing the basic differences, but it does not provide enough detail to know the comparison between 365 and 375: http://glowpaints.co.uk/how-to-test-a-uv-lamp.htm


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## Norm (Dec 10, 2014)

I have a custom made Peak With three Nichia NSPU510CS 375 nm LEDs, see this thread. 

Search the forum for Nichia NSPU510CS and you'll find other 375 nm threads. 

I find for general mucking around it works very well. 

Norm


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## PhotonWrangler (Dec 10, 2014)

The 365nm LEDs that I have seem to be slightly weaker than 375nm LEDs I've played with. The contrast of the materials being fluoresced are very slightly better, but also a little dimmer overall, if that makes sense.

I have a 1w 365nm flashlight at my desk right now as well as a cheap 5mm 395nm squeeze light. Aiming both of them at a fluorescent plastic case, the cheap 395 light fluoresces it far brighter than the 1W 385nm light, although there is more visible purple light from the 395nm unit. On the other hand, the 365nm light will show the invisible security markings in paper currency quite well while the 395nm light produces almost no response.

365 and 375 are close enough to each other that I don't think you'll see a strong difference in most applications. The few exceptions would be invisible inks that are specifically designed for a particular wavelength.


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## techwg (Dec 10, 2014)

PhotonWrangler said:


> The 365nm LEDs that I have seem to be slightly weaker than 375nm LEDs I've played with. The contrast of the materials being fluoresced are very slightly better, but also a little dimmer overall, if that makes sense.
> 
> I have a 1w 365nm flashlight at my desk right now as well as a cheap 5mm 395nm squeeze light. Aiming both of them at a fluorescent plastic case, the cheap 395 light fluoresces it far brighter than the 1W 385nm light, although there is more visible purple light from the 395nm unit. On the other hand, the 365nm light will show the invisible security markings in paper currency quite well while the 395nm light produces almost no response.
> 
> 365 and 375 are close enough to each other that I don't think you'll see a strong difference in most applications. The few exceptions would be invisible inks that are specifically designed for a particular wavelength.


Would you be able to take a picture of that example so I can see what your 365 looks like shining on the case and then the 375 one?


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## snijok (Dec 11, 2014)

I believe that GITD and fluorescent materials, which are considered in this thread, have their absorption already at 400nm or even 450nm. Otherwise one will not see any fluorescence at all, if the wavelength is "not enough". The transition from ground state to excited state does not need very much energy (or very short wavelength). On the contrary, the thing which matters is a good match between the energy of excitation light quantum and the energy of the transition to upper state in the fluorescent system. By going to deep UV one may be moving away from the optimum wavelength and thus shorter wavelength UV may be even less efficient for charging GITD and fluorescing. 
One obvious fact is that deeper UV is harder to see both with eyes and camera. Thus, reemitted light will be more saturated and will not have blue component on the photos, as it is clearly seen on the glowpaints how-to page.


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## techwg (Dec 11, 2014)

I understand this, but I am trying to ask if someone can provide a visual between the two specific wavelengths so that I can actually see the degree of difference instead of academically understanding the difference.


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## The Municipality (Dec 30, 2014)

PhotonWrangler said:


> The 365nm LEDs that I have seem to be slightly weaker than 375nm LEDs I've played with. The contrast of the materials being fluoresced are very slightly better, but also a little dimmer overall, if that makes sense.
> 
> I have a 1w 365nm flashlight at my desk right now as well as a cheap 5mm 395nm squeeze light. Aiming both of them at a fluorescent plastic case, the cheap 395 light fluoresces it far brighter than the 1W 385nm light, although there is more visible purple light from the 395nm unit. On the other hand, the 365nm light will show the invisible security markings in paper currency quite well while the 395nm light produces almost no response.
> 
> 365 and 375 are close enough to each other that I don't think you'll see a strong difference in most applications. The few exceptions would be invisible inks that are specifically designed for a particular wavelength.



The 395nm LED only appears brighter because it's illuminating the item with visible light, not because it's actually brighter. A good UV light will only activate fluorescent objects and will leave everything else dark. If you want maximum effect from "black light" reactive items, 365nm is the proper wavelength for this. 

This is a 365nm LED.






With camera flash.


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## avalon11 (Nov 16, 2017)

I got from Ebay 365nm UV LED's and made powerful torch out of 14 of them. They do produce UV but also somewhat white fluorescence. When compared with blacklight tube 365nm seems more like white LED because there is so little fluorescence. I mean range of it, phosphors and cellulose do glow brightly. But with blacklight I could so many invisible things fluorescing.


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## PhotonWrangler (Nov 16, 2017)

A fluorescent blacklight that has "BLB" in the model number includes a deep blue filter that blocks the visible light produced by it's internal phosphor coating. All of the 365nm LEDs I've seen also produce some visible whitish light which has the unwanted effect of diluting the fluorescent response. The worst ones contain plastics that fluoresce, producing unwanted visible light.

A piece of UV filter glass in front of the LEDs should help this. I'm a little surprised that some manufacturers aren't offering this yet.


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## FRITZHID (Nov 16, 2017)

PhotonWrangler said:


> A fluorescent blacklight that has "BLB" in the model number includes a deep blue filter that blocks the visible light produced by it's internal phosphor coating. All of the 365nm LEDs I've seen also produce some visible whitish light which has the unwanted effect of diluting the fluorescent response. The worst ones contain plastics that fluoresce, producing unwanted visible light.
> 
> A piece of UV filter glass in front of the LEDs should help this. I'm a little surprised that some manufacturers aren't offering this yet.




'bout nailed the head on that one PW.
In my exp, ALL "UV" light producing sources ALSO produce visible light.... that being said, yes... UV PASS or Woods' Glass filters are needed to filter out the visible emissions.
TBH, i am very surprised that manufactures haven't added a UV pass "plastic" encapsulation of some sort... kind of like the IR LEDs that are darkly tinted... 
just my $0.02


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## PhotonWrangler (Nov 18, 2017)

FRITZHID said:


> 'i am very surprised that manufactures haven't added a UV pass "plastic" encapsulation of some sort... kind of like the IR LEDs that are darkly tinted...
> just my $0.02



Fritz, this would make so much sence and probably not cost a lot to implement. The only reason I can think of is maybe the UV-passing plastics aren't UV stable over time. That's just a guess.


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## FRITZHID (Nov 19, 2017)

PhotonWrangler said:


> Fritz, this would make so much sence and probably not cost a lot to implement. The only reason I can think of is maybe the UV-passing plastics aren't UV stable over time. That's just a guess.


My thinking as well.... Plastics and UV aren't exactly friendly, from either a degradation issue to having UV blocking issues.
I think there might be a thermal issue as well, most woods glass lights I've used get rather hot... Hotter than normal lights of the same type that is.


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