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Some minerals from my collection

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#1 Hornblende

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Posted 12 January 2018 - 22:23

Hi all,
I just made a black box for taking UVIVF pictures and tested it on some of my minerals. The setup works great ;)

Camera: Canon 6D full spectrum + Carl Zeiss Jena Tessar 50mm f/2.8
UV Lighting: Convoy S2+
Filters: BG40 + Baader UV/IR cut filter on the lens, Baader-U on the Convoy


Red spinels (MgAl2O4). The red color AND fluorescence is due to trace amount of chromium in the mineral.
Attached Image: IMG_0513 copie.jpg
Attached Image: IMG_0511 copie.jpg


Quartz with hydrocarbon inclusions from Tibet. The inclusions are brightly fluorescent with a nice blue color!
Attached Image: IMG_0515 copie.jpg
Attached Image: IMG_0519 copie.jpg


Scapolite (Ca,Na)4Al6Si6O24CO3. That magenta fluorescence is astonishing!
Attached Image: IMG_0520 copie.jpg
Attached Image: IMG_0521 copie.jpg
Attached Image: IMG_0522 copie.jpg
Attached Image: IMG_0523 copie.jpg


Fluorite (CaF2). This specimen is also phosphorescent.
Attached Image: IMG_0531 copie.jpg
Attached Image: IMG_0532 copie.jpg


Zircon (ZrSiO4). Normaly the yellow fluorescence of zircon is seen under short-wave UV, but apparently the Convoy S2+ is so powerful it triggers it.
Attached Image: IMG_0533 copie.jpg
Attached Image: IMG_0536 copie.jpg


I saved the best for last: this is a piece of Hackmanite. It is a very rare, sulfur-rich variety of sodalite Na8(Al6Si6O24)Cl which change color when exposed to UV light. The stone return to its initial color when exposed to yellow light. This can be repeated indefinitely. This interesting phenomenon is called Tenebrescence, more infos here: https://www.gemology...hackmanite.html
Hackmanite is also brightly fluorescent.
Attached Image: IMG_0524 copie.jpg
Attached Image: IMG_0529 copie.jpg
Attached Image: IMG_0528 copie.jpg

Edited by Hornblende, 12 January 2018 - 22:26.


#2 Andrea B.

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Posted 12 January 2018 - 22:46

Wow! Love these. Nice work.

That zircon fluor is so strange.

A new artist's brush or soft nylon paint brush after brushed against some plastic has enough static electricity to gather up a lot of the fluorescent lint prior to shooting. Alternately, canned air to blast it off.
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#3 Cadmium

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Posted 13 January 2018 - 00:07

Hornblende, Very nice!
I am curious what is the textured black background material? It stays very black in UVIVF shots.

#4 Andy Perrin

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Posted 13 January 2018 - 01:47

Fascinating and beautiful! Very nice photos. I like your box setup. Will you do shortwave UVIVF sometime? Such a box seems well-suited to containing the radiation...

Quote

Hackmanite. It is a very rare, sulfur-rich variety of sodalite Na8(Al6Si6O24)Cl which change color when exposed to UV light. The stone return to its initial color when exposed to yellow light. This can be repeated indefinitely. This interesting phenomenon is called Tenebrescence,

I own a Super Takumar 50mm/1.4 that contains radioactive thorium. The thorium radioactivity produces F-centers in the glass (personally, I call them F-bombs) which turn it yellow over time. Exposure to UV will turn the glass clear again. It is apparently the same tenebrescence phenomenon.

#5 Hornblende

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Posted 13 January 2018 - 18:01

Thanks all :)

Andrea: good tip! The fluorescent dust is very annoying, especially in the zircon picture.

Cadmium: The black material is some sort of plastic foam. I found out black polycarbonate is also good for UVIVF but it degrades under UV light...
Attached Image: IMG_6143.JPG

Here is my black box by the way, I put a dark cloth over the opening and the camera. The Convoy+Baader-U sits on the top.
Attached Image: IMG_6142.JPG

Andy: I have a SWUV lamp (a mercury lamp I think). However, I don't have a UV-C pass filter and it would not fit on the lamp. Also SWUV are nasty, I don't realy want to deal with that :(

#6 Cadmium

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Posted 14 January 2018 - 02:25

Hornblende, Thank you for the information and photos of your material and set up.

On a side note, often many UV lamps employ Hoya U-325c filter glass in front of the bulb.
U-325c has an extremely similar transmission profile to U-330, which is almost exactly the same as Schott UG5,
all of which transmit not only UV, but also some blue and green, and even red and IR, so these are not good for fluorescence lighting in my opinion.
I am just saying this for anyone doing fluorescence, this is something to look for and keep in mind.
A much better light filter is U-340 (or UG11), it doesn't leak blue/green at 2mm thick, so it is very good for 365nm UV Nichia light which has no Red/IR that needs to be filtered,
however for other lights, and flash, a stack of U-340 (UG11) 2mm + S8612 2mm would be needed to suppress the Red/IR.
USE YOUR UV EYE PROTECTION GOGGLES:
Basically any filtered light used for fluorescence should not emit any visible light, it should look black.
U-325c, U-330, and UG5 will show blue/violet light, which will contaminate any true visual fluorescence.
Here is a graph of the Hoya U filters, and also one comparing U-330 with UG5.
One might assume in the first graph that all plots are using the same thicknesses of glass, however I believe the U-325c is using 4.5mm thick glass according to their data sheet, and the U-330 plot uses 2.5mm thick glass according to their data sheet.
So I am not sure what exact thicknesses of glass are being used in their comparison graph.

http://www.hoyaoptic...ransmitting.htm
Attached Image: u330_lg.jpg

Hoya U-330 2mm vs Schott UG5 2mm comparison
Attached Image: U330_2mm_UG5_2mm_TD_TL.jpg

Edited by Cadmium, 14 January 2018 - 02:50.


#7 UlfW

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Posted 14 January 2018 - 14:51

View PostAndy Perrin, on 13 January 2018 - 01:47, said:

I own a Super Takumar 50mm/1.4 that contains radioactive thorium. The thorium radioactivity produces F-centers in the glass (personally, I call them F-bombs) which turn it yellow over time. Exposure to UV will turn the glass clear again.

I can confirm that.

I own an old Canon FD35/2.0 that contains thorium-doped glass that had turned yellowish.

After one dose* of exposure by a Convoy S2+, sitting on the rear lens element, the tint had almost disappeared.
*(until my new good battery was discharged)

I helped the process slightly by placing the lens on a pice of aluminium foil, as I could see a fluorescence pattern from the lamp through the lens.
The lens might be at least marginally usable for UV-photography.

The rest of the tint is taken care of, just now, with a freshly charged battery.

Edited by UlfW, 15 January 2018 - 11:06.

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#8 UlfW

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Posted 14 January 2018 - 16:10

An interesting paint that might be used to improve black boxes for UVIVF... is the Semple Black 2.0
https://culturehustl...st-art-material

It is very black, matte and can be thinned with water.
It might be possible to apply with an airbrush, but is quite thick from the beginning.

Member Jonathan should have the credit for finding the paint and sharing that information when he experimented with his references last spring/summer.
I think the bottom square of post#8 here is done with that paint:
http://www.ultraviol...__fromsearch__1

I just painted a small part of a cheap PTFE with the paint and tried it with the convoy S2+.
The painted part is much more dark than the PTFE background, that I suspect is not very pure.
Unfortunately I haven't any UVIVF setup ready yet, and cannot post any picture but the result is clearly visible to my protected eye.
Ulf Wilhelmson
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#9 JMC

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Posted 15 January 2018 - 09:37

You're right Ulf, that bottom square is painted in Semple Black 2.0. I came across this when I needed some easily obtainable black paint that would absorb pretty much any light thrown at it, from UV through to IR. This is readily available and not expensive, and something which is useful for me, from a UK based company so I could get hold of it quickly. I was building a rig to measure flash power of a UV converted flash and an unmodified one so I could see the difference. The build was a wood box with a mount for a flash at one end and a spectrometer at the other.
Attached Image: IMG_1558small.JPG
The spectrometer has a cosine corrector on it so picks up light from a 180 degree field of view. The spectra from the 2 flashes are shown below;
Attached Image: Norm and UV flash comp UVIVF.jpg
What I didn't bother paying any attention to before was the visible wavelength part of the UV flash. Other than a slight tail in the blue end of the spectra from the filter used on the flash, basically noise in the visible part. That would suggest to me that the Semple 2.0 paint does not fluoresce significantly under UV.

I must stress this experiment was not set up to show fluorescence - I am merely inferring that from data I have. However given it costs about $15 for enough paint to cover a couple of square meters, and would allow you to custom make your own boxes for UVIVF work, it's perhaps worth a try by someone more involved with UVIVF work.

As a side note, the story behind the paint is worth a read, and a chuckle;
https://www.youtube....h?v=MilZ1v5uD8s

Edited by JMC, 15 January 2018 - 09:37.