UVIVF: Shortwave (254nm / UV-C) vs. Midwave (UV-B) vs. Longwave (395nm / UV-A)

[Andrea B.]

Just worried about you frying your toes or something !!!!!

 

I don't think we can really say that the UV-LED torches are more powerful than the sun ?? Terms are not defined and so forth. But it was funny anyway !!

(And I do wonder how accurate PS is......)

 

Be careful out there!! :D

[Pylon]

the LED radiation itself is not more powerful than the sun's radiation if you were to measure the radiation level directly at the source - the sun is much more powerful at the source, but because it is so far away, by the time it actually hits my foot, the LED radiation is more powerful when measured on my foot. I can objectively measure UV-A using my full-spectrum camera with the Baadar-U filter. Looking at the picture, my shoe was receiving 4X as much radiation when compared to the sun, because my right shoe was 2 stops brighter.

[Pylon]

I was using a shortwave 4W lamp I purchased from eBay some time ago, I took 2-4 10-30 second exposures with it, holding it in my hand, pointed away from me, with a wool beanie and sweatshirt hood over my head, a scarf covering the bottom of my face, a sweatshirt, and jeans. Here is the thing, I believe I had my eyes closed for about half the time I was using that light, however the other half, my eyes were open and I had safety goggles on, however the safety glasses I had on were only rated for UV-A protection, not UV-C protection.... So, I just got exposed to a few minutes of UV-C light because of not being mindful enough of which glasses I had over my eyes. Luckily it was only 4W and only a few minutes of exposure, however I'd rather play it safe and not turn that thing on again until I come up with a better solution for protecting my eyes and face, as even the UV-C glasses I do have do not fully seal (they are orange too, something clear would be much better). I think the ideal solution would be a clear face shield that also has an additional fabric material attached to it that covers the sides, back and top of the head.

 

Also: what about sunscreen with UV-C? Would that work?

 

UV-A, UV-B, vs. UV-C Induced Visible Fluorescence, un-modded Nikon D810 with no UV/IR cut filter

 

vs. visible:

 

UV-A vs UV-C Induced Visible Fluorescence, un-modded Nikon D810 with no UV/IR cut filter

[Pylon]

So now we need to compare UV-in-sunlight's intensity of 4.08 mW/cm² to the output of a 365nm Nichia UV-LED.

We also can set a limit in seconds for exposure to the Nichia output.

 

To do this properly you must know what kind of Nichia chip your torch is using because there are different grades of Nichia chips.

 

So if anyone has any Nichia intensity output data, let me know and I will divide it into 1000 for you. :D :P

 

According to this page, the MTE-301 uses the NCSU033B chip.

 

[lost cat]

Would be nice to see examples of visible flourescence of the exact same objects/material but under different UV lighting. Haven't seen any posts about this topic on this forum.

 

I'm very early in my tests, but mirrors look interesting under shortwave, as do minerals. Need to do many more comparison tests.

 

What shortwave/midwave lights can you reccomend? It would be ideal to get one light that has all 3, and that is bright.

 

Depends on the fluorescent material but I imagine the visible fluorescence will look exactly the same whether excited with 254nm, 351 or 379nm photons assuming the photons are exciting the same transition. The extra energy of the excitation photon simply is lost through the thermal transitions before hitting the excited ground state to release a fluorescence photon. Whether you excite with UVA, UVB or UVC the fluorecence may still be green. You might reach other transitions though as you change the wavelengths including greater absorption, phosphorescence raman, and whatnot.

 

 

If money were no object (and I had a team of grossly underpaid yet eager graduate students) I'd have them perform the experiment using an OPO laser. OPOs can provide a near continuous band of laser wavelengths options from 210-2400 nm. Clear laser goggles should provide adequate eye protection for the UV.

 

The cheaper option would be to use a deuterium/tungsten lamp and prisms.

[Andrea B.]

My understanding is that fluorescence in a fluorophore is induced by rather a specific excitation wavelength. The visible (or other) emission is also confined to a peak wavelength. For example, the chlorophyl-A in a green plant is excited to fluoresce at around 440 nm. I've forgotten what is its peak emission wavelength in the red/orange range.

 

The point being that you might not get fluorescence in a particular subject with some excitation wavelengths. Of course the UV lights we typically use are generally broadband so we may not be sure which wavelength is causing the excitation. "-)

 

As an example, I found this table of fluorescent dyes used in biological research which shows the peak excitation/emission wavelengths.

http://www.iss.com/r...uorophores.html

 

[side Note: We had a very interesting discussion here (started by member Oldoinyo) about whether the Bayer dyes in our cameras fluoresced under UV light and how that might affect the recording of our UV photos.]

[Alaun]

Just another little side note comes to mind, about about fluorescence: Some colors of the printing on lenses do fluorescent, most prominent (what I found) is the yellow printing on the prince galaxy lens. This might have an issue with UV-photography, when the filter is in front of the lens, but I think the effect is small.

[Andrea B.]

We've also seen some fluorescence in the lens element glues or from other internal parts. Such fluor from lettering, glues, or other stuff could cause a little flare? As Werner observes, the effect is likely so small that the photo does not get that "washed out" effect. Experiments will tell the tale.