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UltravioletPhotography

diy Long-, Medium-, and Short-Wave UV Lamp for UV Fluorescence Photography


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Hi!

 

I just posted a new whitepaper with a short primer on UV Fluorescence Photography and a diy 18W, 3-wavelength, professional-grade lamp.

 

The attached figure shows pictures of Hackmanite from Bancroft, Ontario, Canada taken using this diy lamp: a) White light photograph; b) reflected near-UV with Baader-U and long-wave illumination; c) fluorescence with wideband (LW, MW and SW) excitation; d) long-wave UV excitation; e) fluorescence with mid-wave UV excitation; f) fluorescence with short-wave UV excitation.

 

The whitepaper is available at: http://uvirimaging.c...ce-photography/

 

post-62-0-14773400-1475445536.jpg

post-62-0-54983200-1475445536.jpg

 

Cheers,

 

David

www.UVIRimaging.com

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Hi David -- Thank you for the post and the link to your UV tube lamp. That's a nice paper!

 

I'm also pleased that you provide lots of warnings about the hazards of shortwave UV radiation.

B)

 

 

From paper: ........ Standard DSLR cameras are very insensitive to UV, and lens optics are usually very obscure to UV wavelengths, so a barrier filter is not usually needed when th excitation waveength is outside the visible range and the source includes a sufficiently narrowband excitation.

 

Well, mostly true. However, as a Good Practice, I recommend always using a barrier filter when performing visible fluorescence photography with either a converted or non-converted DSLR or mirrorless camera. You would be surprised* what can get through the camera's internal filtration which is often not as robust as we would like (and which is sometimes just plain weird - like omitting violet, for example). Using a barrier filter for UV induced visible photography also keeps us in practice for the time when we might want to switch to photography of IR fluorescence or specific R, G or B fluor. Another reason for using the barrier filter is that some UV sources - like 365nm Nichia chip UV-LEDs - emit a bit of light in the visible violet range which would be recorded as a contaminant in the visible fluorescence photo.

 

*You would be surprised -- No, you would not likely be surprised as I'm sure you've performed your own "forcing" experiments at some time or other, right?!? :D

 

A question for you: are there any UV tubes which have a peak wavelength between the 315 nm and 365 nm version which you have illustrated in your paper? I'm just curious.

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enricosavazzi

A question for you: are there any UV tubes which have a peak wavelength between the 315 nm and 365 nm version which you have illustrated in your paper? I'm just curious.

This is a general limitation of the mercury vapor emission spectrum. In the UV, it emits mostly a line around 312 nm and a (usually higher) peak at 365 nm. It also has a weaker line at 334 nm which could be isolated with a bandpass filter and used for UV imaging. Aside for these three lines, not much else of the Hg emission spectrum is directly useful for our UV imaging.

 

It is of course possible to coat the inside (or outside) of the tube with a phosphor that is excited by the 254, 300 and/or 312 nm lines and emits at some other (lower) UV wavelength(s). I believe that at least some commercial UV lamps use a UV-fluorescent coating to enhance the 365 nm emission band by down-converting the shorter wavelength peaks, while others (usually the cheaper ones) use only a UVC-,UVB- and VIS-cut coating to transmit only (or mostly) UVA, and in this case, in practice, just the 365 nm line. I would expect the emission band of this type of phosphor to be broader than the Hg emission lines.

 

Xenon-arc lamps emit a much more continuous UV spectrum, so this is the type of lamp that I would regard as most interesting for applications where a more-or-less continuous UVA emission spectrum is desired.

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Thanks, Enrico!!

 

I'm adding some of this info to the UV Sticky in the UV Lighting section with attribution to you.

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