• Ultraviolet Photography
  •  

UVF Alabaster

Fluorescence
7 replies to this topic

#1 Adrian

    Member

  • Members+G
  • 199 posts
  • Location: Ashtead, Surrey, UK

Posted 06 March 2020 - 10:50

Inspired by Andrea's recent post about whether Alabaster could be used as a test target for UVF "white balancing".
I purchased a small Alabaster statuette on eBay for 5GBP. It arrived in a broken state, which actually was very helpful, as it has both weathered surfaces and clean fresh surfaces.
I photographed it with a Convoy S2+ UV torch with Hoya U-340 filter. I loaded this image into PhotoNinja, and colour corrected it using the light area under the chin. I copied these settings, and applied them to an an image of False Acacia (Gleditsia sp.) showing the core wood fluorescing in UV. The blue cast on the Gleditsia has been pretty much neutralised. Will continue to do more testing!

Technical details:
Nikon D801 with 105mm micro Nikkor lens. UVF image "light painted" with Convoy S2+ UV torch, and Hoya U-340 filter. 15 seconds @ f/16

Interestingly, I have an old (I suspect rare book) called "Ultraviolet Rays and their Use in the Examination of Works of Art", by the Metropolitan Museum of Art, NY, in 1931
There is a fascinating section there on the use of UV for showing cracks etc, and states that recent breaks "fluoresce white as the original surfaces". This is not borne out by my images!
There is a great picture of the "UV apparatus" used, which, if anyone is interested, I will post here.

L to R: Visible, UV-induced Visible Fluorescence, White Balanced UViVF
Attached Image: Alabaster comp.jpg

Top to Bottom: Visible, UV-induced Visible Fluorescence, White Balanced UViVF
Attached Image: Gleditsia comp lo res.jpg
Adrian Davies
www.imagingtheinvisible.com

#2 colinbm

    Member

  • Members+G
  • 2,748 posts
  • Location: Australia

Posted 06 March 2020 - 11:50

They are some crazy colours Adrian.

#3 Andy Perrin

    Member

  • Members+G
  • 4,425 posts
  • Location: United States

Posted 06 March 2020 - 14:52

Adrian, I think I need some help understanding what you did here. The alabaster statue has three images. The first looks like visible-reflected light to me, but what's the difference between the other two? Are they both UVIVF?

#4 dabateman

    Da Bateman

  • Members+G
  • 3,006 posts
  • Location: Maryland

Posted 06 March 2020 - 15:52

My guess was first image is visible, second is UVIVF, then third is WB corrected under statue neck.
The wood is very interesting and makes me wonder if this is something good to keep an eye on.
If I can't dial in a WB its hard to get the color.


#5 Andrea B.

    Desert Dancer

  • Owner-Administrator
  • 9,115 posts
  • Location: UVP Western Division, Santa Fe, New Mexico

Posted 06 March 2020 - 18:08

Adrian, this is a good experiment. Thank you!

I'm thinking, however, that a specimen of alabaster which is not old and/or stained might work better? So I'm wondering if a specimen purchased at one of those rock & mineral stores might be more useful. (Does England have rock & mineral stores like we do here in the US?)

--> Adrian, I have taken the liberty of labeling the statue photos because I was also not quite sure - initially - which was what. Please improve upon those labels as you might see fit. Thanks.

An important outcome here is that it does seem to be possible to find some material close to white fluorescent which can be used for a white balance to be saved and applied to other fluorescence photos to bring out their "true" colors.
Andrea G. Blum
Often found hanging out with flowers & bees.

#6 Andrea B.

    Desert Dancer

  • Owner-Administrator
  • 9,115 posts
  • Location: UVP Western Division, Santa Fe, New Mexico

Posted 06 March 2020 - 18:10

P. S. Yes, I would enjoy seeing a post of the set-up from that interesting old book you found "Ultraviolet Rays and their Use in the Examination of Works of Art", by the Metropolitan Museum of Art. We are all so digitally attuned these days that we forget UV was being used "way back" in the analog age for art conservation needs. :grin:
Andrea G. Blum
Often found hanging out with flowers & bees.

#7 Øivind Tøien

    Member

  • Members+G
  • 198 posts
  • Location: Fairbanks, Alaska

Posted 07 March 2020 - 06:01

Very nice example. The UVIVF blue and yellow color of the wood is very similar to what I captured here (white balanced based on visual impression):
https://www.ultravio...w-in-the-woods/

Edited by Øivind Tøien, 07 March 2020 - 06:06.

Øivind

#8 Adrian

    Member

  • Members+G
  • 199 posts
  • Location: Ashtead, Surrey, UK

Posted 07 March 2020 - 11:55

Apologies for lack of captions to the mages, and thanks to Andrea for adding them. The final, corrected, UVF image of the wood is closer to what my eye sees.
Adrian Davies
www.imagingtheinvisible.com