NikonGear'23
Gear Talk => Other => Topic started by: elsa hoffmann on April 25, 2017, 09:59:25
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C P Burrows:
I Photographed The Invisible Light That Plants Emit -
I've photographed hundreds of glowing flowers since 2014 after seeing Oleksandr Holovachov's work with ultraviolet-induced visible fluorescence (UVIVF) photography.
Each time I do a set of UVIVF photos, it starts with going out under the cover of darkness to snatch unsuspecting flowers growing around the neighborhood. I rarely know what to expect from a flower before I get it back to shoot. Some I think will dazzle end up flopping, and others I am surprised by their colors or light. Every one is a surprise!
In the same way a tee-shirt blue glows under a black light, most organic material glows at least a little with UV stimulation and in all kinds of colors. To make the most of it, I make sure I'm working in the darkest environment I can and use a 365nm light so the camera can't see the UV light.
Any time the flowers are hit by sunlight, they're letting off their own glow in response and it's simply overwhelmed by the sunlight we can see. These photos capture something we always see, but never can observe.
More info: cpburrows.com
http://www.boredpanda.com/i-photograph-flowers-hidden-light-with/
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Thanks for the pointer. Many of the authors on our 'sister' site, http://ultavioletphotography.com, now present results of UVIFV (ultraviolet induced visible fluorescence) for flowers and other natural subjects. Always astonishing appearances to behold. So it is good to see the stuff getting attention from a wider audience.
A small technical nit-pick, which really goes to the originator ( C.P.Purrows) : plants usually don't emit light, they reflect it, more or less unaltered. Bioluminescence is known in some parts of the plant kingdom, but doesn't depend on light as such.
We don't know for certain what - if any - evolutionary significance UVIVF has in Nature. Maybe it is just a spurious result from internal biochemical processes occurring in the plant's foliage and floral parts. Still, the often dramatic difference in UVIVF from say nectaria vs other parts of the flowers can tickle our imagination.
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UVIVF can be pressed into service as a photographic tool on its own. Use some substance or liquid that really has high fluorescence and play with this to your heart's content. Effects can be highly enjoyable.
If you don't wish to use fluorescing paint, Tonic Water is a familiar source for excellent fluorescence. Here it is used to illustrate Liebig's law of the minimum ('Law of the Minimum'), a law applicable to agriculture and ecology in general. I employed a broken wine glass to this end before throwing it into the bin.
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LWUV-induced resonance fluorescence
(http://www.pbase.com/bobfriedman/image/109196158/original.jpg)
(http://www.pbase.com/bobfriedman/image/109731104/original.jpg)
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Elsa, this is an interesting read, and the sampled images are beautiful.
FWIW, my avatar is also a UVIVF campanula. ;)
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UVIVF can be pressed into service as a photographic tool on its own. Use some substance or liquid that really has high fluorescence and play with this to your heart's content. Effects can be highly enjoyable.
If you don't wish to use fluorescing paint, Tonic Water is a familiar source for excellent fluorescence. Here it is used to illustrate Liebig's law of the minimum ('Law of the Minimum'), a law applicable to agriculture and ecology in general. I employed a broken wine glass to this end before throwing it into the bin.
Much sexier than Liebig's Barrel ;)
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I em enjoying the replies - thank you
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What kind of lamps are used for this type of photography?
Do I understand that the camera used is standard visable light dSLR?
Is a filter used on the lens? Is a Nikon L37c or L39 acceptable?
Thanks!
Dave
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We don't know for certain what - if any - evolutionary significance UVIVF has in Nature.
Many brightly coloured flowers use this effect so they appear brighter than other flowers which reflect just visible light. A flower which is more eye-catching to potential pollinators will have an evolutionary advantage.
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What kind of lamps are used for this type of photography?
Do I understand that the camera used is standard visable light dSLR?
Is a filter used on the lens? Is a Nikon L37c or L39 acceptable?
Dave
I use a 365nm UV torch called Tank007 bought from ebay to induce the visible fluorescence. The torch emits a slight amount of visible light which is cut by a Baadar U (UV bandpass) filter. You need nothing special on the camera or the lens, not even L37/39/41C filters, so long as the UV light source contains no visible portion, and you take the pictues in the total darkness.
Here's another humble example: UVIVF Oncidium.
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Just picked this up on NAT GEO
The inside workings of plants are the unexplored frontier of botany. What happens when a nematode or fungus attacks a crop? How does this stress affect the plant, and how does it physically change the roots, stem, and flowers?
Japanese researchers have devised a way to find out: Make the plant transparent. With a chemical bath, they reduce the plant’s visible chlorophyll, the pigment that makes it green. Days to weeks later the entire plant becomes clear, and scientists can observe its inside tissue at a cellular level.
and for more:
http://www.nationalgeographic.com/magazine/2017/05/explore-transparent-plants/?utm_source=Facebook&utm_medium=Social&utm_content=link_fb20170505ngm-transparentplants&utm_campaign=Content&sf75016501=1
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How are the plant scientist going to improve tobacco? More nicotine, less tar? Maybe fire retardant tobacco? "Spit thou only in the corner." (Massachusetts Bay Colony Etiquette).
I thought all they had to do was splice in a few genes from a squid and Monsanto!
Oh no, they say he's got to go go go Godzilla
Oh no, there goes Tokyo go go Godzilla
History shows again and again
How nature points up the folly of men
--BOC
Elsa,
Your plant scientist are scaring me. :)
Dave
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David - as far as photography goes - interesting photo opportunities I suppose. Fascinating indeed. We want to document everything in any way we can - never-mind what it takes to get there. And we also use photos as proof of what we see.
The off-topic part of this article (and ye it is more about that, than photography): modified food has been with us for a couple of decades. The results of research is "spectacular" and yields in crops phenomenal. Nothing less. Apart from the fact that it kills us and the environment, which seems to be less important as money talks loudly. But then - why should this have the exclusive on destroying the world. Us humans do a pretty good job - essentially acting like viruses - to keep destroying the planet till there is nothing left.
In the interim - to be philosophical - we, who shoot, - document the whole process. It's like a war - you cover it from deployment - to death..... No one wins, except the arms suppliers.
Don't shoot the messenger.
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LWUV-induced resonance fluorescence
(http://www.pbase.com/bobfriedman/image/109196158/original.jpg)
(http://www.pbase.com/bobfriedman/image/109731104/original.jpg)
Hi! I´m new here...
Congratulation for these pictures!! They are amazing!!
If you don`t mind... how did you do them?
I´m studying to take photos with UV light... I have a 365nm UV light and a IR filter, but all the photos get very dark... even with 3 minutes of long exposure. I can´t see nothing. I already tried to correct the exposure at photoshop, but the flower doesn`t show up. !
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I use a 365nm UV torch called Tank007 bought from ebay to induce the visible fluorescence. The torch emits a slight amount of visible light which is cut by a Baadar U (UV bandpass) filter. You need nothing special on the camera or the lens, not even L37/39/41C filters, so long as the UV light source contains no visible portion, and you take the pictues in the total darkness.
Here's another humble example: UVIVF Oncidium.
Hi! So we need to use the filter on the UV light? I put it on the lens... And my filter is a IR filter. The filter must be UV, not IR? Sorry, I don´t understand these things very well... And the UV light must be invisible? The one I bought is invisible during the day, but at the dark I can see the "blue light". So this one can`t be used? (Sorry for any English`s mistake, I speak portuguese)
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I use a 365nm UV torch called Tank007 bought from ebay to induce the visible fluorescence. The torch emits a slight amount of visible light which is cut by a Baadar U (UV bandpass) filter. You need nothing special on the camera or the lens, not even L37/39/41C filters, so long as the UV light source contains no visible portion, and you take the pictues in the total darkness.
Here's another humble example: UVIVF Oncidium.
Akira, can you be more specific? I'm not sure which mode flashlight one should buy and I'm looking at fillers that coast $300.00 to $400.00 (USD). This is a fright fest!
Dave Hartman
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Hi! So we need to use the filter on the UV light? I put it on the lens... And my filter is a IR filter. The filter must be UV, not IR? Sorry, I don´t understand these things very well... And the UV light must be invisible? The one I bought is invisible during the day, but at the dark I can see the "blue light". So this one can`t be used? (Sorry for any English`s mistake, I speak portuguese)
Hi, Castorelle. Welcome to NG.
First of all, you need to understand that UV induced visible fluorescence and photographing reflected UV are two completely different worlds.
In this thread, we are talking about UV induced visible fluorescence. That means, the UV light is used to induce the fluorescence. UV light is invisible but the induced fluorescence is visible. All images posted in this thread are the captures of visible image.
On the other hand, something like the "bull's eye" pattern of the flower belongs to the reflected UV photography. The captured image is invisible.
So, you need very different equipments for each. In order to capture the images posted here (UV induced visible fluorescence), you need:
1. A UV flashlight (you already have an appropriate one).
2. Either one of these:
2a. A special filter that passes only UV light (around 365nm) which should be put on the flashlight.
2b. A light yellow filter (Y44 or similar) to cut the visible portion of UV flash light which should be put on the camera lens.
An IR filter is not needed or makes no sense in any way, so long as you use UV LED flashlight as a light source.
If you go for the option 2b, the color of the fluorescence may not be the same as you would see with the naked eye. The blue fluorescence wiil turn to green.
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Akira, can you be more specific? I'm not sure which mode flashlight one should buy and I'm looking at fillers that coast $300.00 to $400.00 (USD). This is a fright fest!
Dave, the UV flashlight I bought from ebay is "TK566" by Tank007 (sorry Tank007 seems to be the name of the brand and not the model name).
The UV bandpass filter I use for the flashlight is the 1.25" Baader Venus U filter made by Baader Planetarium:
http://www.baader-planetarium.com/de/u-venus-filter-(350nm).html
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I really love the images in this thread. Akira, do you have the long version of the flashlight or do you find that one AA battery version is enough?
Those Venus filters are really pricey... Which size filter fits the flashlight? Somewhere I have a blacklight (Mineralight) that I saved from being thrown away. While the wavelengths of UV from that light might be unhealthy and the batteries are dead, perhaps the filter could be used.
Finding a dark place around here at this time of the year can be a challenge though... Perhaps a small dark box could be constructed.
Any good source of UV-protective glasses?
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Akira,
Thank you for the information. I'll check it out soon.
Dave
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I really love the images in this thread. Akira, do you have the long version of the flashlight or do you find that one AA battery version is enough?
Those Venus filters are really pricey... Which size filter fits the flashlight? Somewhere I have a blacklight (Mineralight) that I saved from being thrown away. While the wavelengths of UV from that light might be unhealthy and the batteries are dead, perhaps the filter could be used.
Finding a dark place around here at this time of the year can be a challenge though... Perhaps a small dark box could be constructed.
Any good source of UV-protective glasses?
Øivind, my TK-566 is the longer version that uses two AA batteries. I haven't used the one AA version, but I think the stronger the better, so long as you compare these particular ones. Needless to say, the the longer version is more powerful and can induce the fluorescence more easily.
The Baader Venus U filter (even the smaller, 1.25" version) is indeed pricy. I was just lucky enough to receive mine from my UV friend "V" as recompense for my effort to find and send him some items only found in Japan.
The 1.25" filter doesn't fit directly on TK-566, and I found a 31.7mm (1.25") to C mount adpter by BORG whose C mount hole fits right onto the head of the flashlight. I fixed the adapter to the flashlight with the self-adhesion tape. This is the adapter:
http://www.tomytec.co.jp/borg/products/partsDetail/summary/238
That said, the hindsight tells me that I could simply fix the filter onto the flash head with the black Permacel tape.
As for the UV protection, I use UVEX 9195 999 goggle. It looks transparent, but it can completely block the fairly strong TK-566 light.
Hope the info would be of any help.
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Nikongear's "Sister Site": UltravioletPhotography.com (http://www.ultravioletphotography.com) has some info about UV-induced visible fluorescence photography which might be helpful.
Short Intro to UVIVF: <> Sticky :: UV-Induced Visible Fluorescence <> (http://www.ultravioletphotography.com/content/index.php/topic/1456-sticky-uv-induced-visible-fluorescence/) by Andrea B.
Photo Board: UV Fluorescence & Luminescence (http://www.ultravioletphotography.com/content/index.php/forum/227-uv-fluorescence-luminescence/)
A post by Alex Holovachov: My UVIVFL journey (http://www.ultravioletphotography.com/content/index.php/topic/1108-my-uvivfl-journey/)
Damon's fluor mushrooms: Mushrooms and friends (http://www.ultravioletphotography.com/content/index.php/topic/1093-mushrooms-and-friends/)
Article: Examples of UV-induced Fluorescence (http://www.ultravioletphotography.com/content/index.php/topic/181-examples-of-uv-induced-fluorescence/) by our very own Bjørn-Birna Rørslett
WB Target: I'm just now testing a new standard target for making an in-camera white balance setting under UVIVF conditions. Experiment 1: First Look at Target-UV & UV-Grey for U... (http://www.ultravioletphotography.com/content/index.php/topic/2253-experiment-1-first-look-at-target-uv-uv-grey-for-uvivf-see-post-7/page__fromsearch__1)
Sticky: Everything you ever wanted to know about UV/IR filters and then some: <> Sticky :: UV/Vis/IR Filters <> (http://www.ultravioletphotography.com/content/index.php/topic/663-sticky-uvvisir-filters/)
Tag Search: All posts about UV illumination (some about UV-flash and some about UV-Led flashlights/torches): UV Lighting
UV-Induced Visible Fluorescence of Satsuma Tangerine under Blacklight
f/11 for 3" @ ISO-400 in Darkness
The 2nd foto is a close-up of the tangerine's skin.
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Hi, Castorelle. Welcome to NG.
First of all, you need to understand that UV induced visible fluorescence and photographing reflected UV are two completely different worlds.
In this thread, we are talking about UV induced visible fluorescence. That means, the UV light is used to induce the fluorescence. UV light is invisible but the induced fluorescence is visible. All images posted in this thread are the captures of visible image.
On the other hand, something like the "bull's eye" pattern of the flower belongs to the reflected UV photography. The captured image is invisible.
So, you need very different equipments for each. In order to capture the images posted here (UV induced visible fluorescence), you need:
1. A UV flashlight (you already have an appropriate one).
2. Either one of these:
2a. A special filter that passes only UV light (around 365nm) which should be put on the flashlight.
2b. A light yellow filter (Y44 or similar) to cut the visible portion of UV flash light which should be put on the camera lens.
An IR filter is not needed or makes no sense in any way, so long as you use UV LED flashlight as a light source.
If you go for the option 2b, the color of the fluorescence may not be the same as you would see with the naked eye. The blue fluorescence wiil turn to green.
Thank you a lot Akira!! So I made a great confusion with IR and UV photography ... :)
The photos I want to take are just like the ones are posted here, but I thought it had another name, with the word "IR". Now that I know the correct name (UV induced visible fluorescence) it will be easier to search informatition for learning more about it.
I will buy this special filter for the flashlight, you said at 2a.
Thanks again!
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Nikongear's "Sister Site": UltravioletPhotography.com (http://www.ultravioletphotography.com) has some info about UV-induced visible fluorescence photography which might be helpful.
Short Intro to UVIVF: <> Sticky :: UV-Induced Visible Fluorescence <> (http://www.ultravioletphotography.com/content/index.php/topic/1456-sticky-uv-induced-visible-fluorescence/) by Andrea B.
Photo Board: UV Fluorescence & Luminescence (http://www.ultravioletphotography.com/content/index.php/forum/227-uv-fluorescence-luminescence/)
A post by Alex Holochov: My UVIVFL journey (http://www.ultravioletphotography.com/content/index.php/topic/1108-my-uvivfl-journey/)
Damon's fluor mushrooms: Mushrooms and friends (http://www.ultravioletphotography.com/content/index.php/topic/1093-mushrooms-and-friends/)
Article: Examples of UV-induced Fluorescence (http://www.ultravioletphotography.com/content/index.php/topic/181-examples-of-uv-induced-fluorescence/) by our very own Bjørn-Birna Rørslett
WB Target: I'm just now testing a new standard target for making an in-camera white balance setting under UVIVF conditions. Experiment 1: First Look at Target-UV & UV-Grey for U... (http://www.ultravioletphotography.com/content/index.php/topic/2253-experiment-1-first-look-at-target-uv-uv-grey-for-uvivf-see-post-7/page__fromsearch__1)
Sticky: Everything you ever wanted to know about UV/IR filters and then some: <> Sticky :: UV/Vis/IR Filters <> (http://www.ultravioletphotography.com/content/index.php/topic/663-sticky-uvvisir-filters/)
Tag Search: All posts about UV illumination (some about UV-flash and some about UV-Led flashlights/torches): UV Lighting
UV-Induced Visible Fluorescence of Satsuma Tangerine under Blacklight
f/11 for 3" @ ISO-400 in Darkness
The 2nd foto is a close-up of the tangerine's skin.
Andrea, very good stuff!! Lots of things to read! Thank you!! And it's a good idea to photograph fruit. I will try too!
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Thanks Akira and Andrea for further information. This is becoming a nice thread for reference. I might just get the flashlight (and UV goggles!) and experiment with the filter from the old Mineralight.
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Here's an image of the removed flashhead of TK-566. The silver ring around the thread is the bottom part of the BORG adapter I mentioned above.
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Thanks for posting the image Akira,
I ordered this 20mm filter at $8 on ebay that as a start can be taped to the front of the TK-566. The spectrum (red line in the link) looks promising:
http://www.ebay.com/itm/262986004673 (http://www.ebay.com/itm/262986004673)
(The filter of the Mineralight let though violet light from a regular LED flashlight)
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LWUV-induced resonance fluorescence
(http://www.pbase.com/bobfriedman/image/109196158/original.jpg)
(http://www.pbase.com/bobfriedman/image/109731104/original.jpg)
Stunning Results!!!
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Thanks for posting the image Akira,
I ordered this 20mm filter at $8 on ebay that as a start can be taped to the front of the TK-566. The spectrum (red line in the link) looks promising:
http://www.ebay.com/itm/262986004673 (http://www.ebay.com/itm/262986004673)
So long as the chart is trustworthy, ZWB1 seems to work (looks like Hoya U340 equivalent).
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Time will show once everything arrives. In the mean time, with 24h daylight here at this time of the year I wonder if something like a large changing bag, with a homemade internal frame added could be used instead of the non-existing dark closet in my cabin (could also be used in the field). For example:
https://www.bhphotovideo.com/c/product/70983-REG/Kalt_NP10102_Large_Changing_Bag_Double.html (https://www.bhphotovideo.com/c/product/70983-REG/Kalt_NP10102_Large_Changing_Bag_Double.html)
The lens would be stuck through one of the arm holes. perhaps the other arm hole can be used for a cable switch for the framing/focusing light that would have to be mounted inside. Have anyone here played with something like this who would like share their experiences?
(https://static.bhphoto.com/images/images500x500/1233295082000_70983.jpg)
[Kalt Large Changing Bag Double Zipper (27 x 30")]
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Looks like I overestimated how dark it needs to be. A dark rainy night yesterday, and a test to see if it is possible to induce vis. light induced florescence with a hand triggered SB600 gave completely black frames at 15 sec exposure at 1600 ISO and f/4 in my kitchen with curtains drawn. So I am abandoning the changing bag idea for now although reports from anyone who used it for this purpose, for instance in the field, would still be welcome.
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Changing bags == sure-fire method for getting dust everywhere you really didn't want it to be
Bad in the good old days for loading sheet film into holders, even worse if you contemplate fluorescence photography. There will be bright fluorescent lint everywhere in the photo.
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I never owned a changing bag. Is that OK?
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Changing bags == sure-fire method for getting dust everywhere you really didn't want it to be
Bad in the good old days for loading sheet film into holders, even worse if you contemplate fluorescence photography. There will be bright fluorescent lint everywhere in the photo.
Thanks, another reason to abandon that idea then.
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The UV-light arrived quite quickly. So I set out with safety glasses and gloves for some first experiments although the UV high pass filter has not arrived yet so there is also a reflected visible light component in the blue-violet range in these. Petals are blue in visible light on both of these flowers.
#1
(http://otoien.zenfolio.com/img/s5/v125/p2376027776.jpg)
D7100 unmodified, f/8 @ 55 mm, 4s, ISO 100, very heavy crop. Nikon L-39 filter on lens.
#2
(http://otoien.zenfolio.com/img/s9/v93/p2376028473.jpg)
D7100 unmodified, f/8 @ 55 mm, 10s, ISO 100, some crop, Nikon L-39 filter on lens.
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This is beautiful work!
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Yes, these look beautiful as they are. I'm looking forward to seeing the results with the VIS-cut filter.
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Thanks for the kind comments both of you and thanks again for the help Akira. It is very inspiring to explore this new world. (It is a little bit like getting an underwater world on the surface.) I am looking forward to when the filter arrives.
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The ZWB1 filter for my Tank 007 TK-566 UV torch arrived. Interestingly the before - after shots I took of a dragonfly were very similar, more variation from hand holding the flashlight. The UV flashlight already came with some kind of filter glass, although some weak blue-violet was visible when viewed from the front side as I recall. The ZWB1 filter was a perfect fit to be just attached with electrical tape to the front (might look for a more stable solution later), and looks dark to the eye except for fluorescent dust specs. With the filter attached, ball bearings look black, perhaps with only a tiny barely visible speck, and the same when photographed in IR, so generally a black frame. Only when the UV flashlight was held at a less than 5cm distance did a clearer highlight spec of the ball bearings show up in IR. Thus it looks like it is not necessary to spend $300 on a Baader-U for this purpose.
First some more captured from before the filter arrived with D7100, L-39 filter on the lens, 55mm f/3.5 AI micro as I recall on PN-11, @ f/8 nominal, exposure typically 4-8 seconds.
Visual light:
#1
(http://otoien.zenfolio.com/img/s10/v106/p2389141961.jpg)
UVIVF all the following, some contamination from nearby fluorescent objects likely in this one:
#2
(http://otoien.zenfolio.com/img/s10/v109/p2389141965.jpg)
#3
(http://otoien.zenfolio.com/img/s4/v65/p2389142039.jpg)
#4
(http://otoien.zenfolio.com/img/s9/v87/p2389141957.jpg)
#5
(http://otoien.zenfolio.com/img/s1/v49/p2389141959.jpg)
#6
(http://otoien.zenfolio.com/img/s12/v180/p2389142031.jpg)
#7
(http://otoien.zenfolio.com/img/s3/v40/p2389141958.jpg)
Horsetails
#8
(http://otoien.zenfolio.com/img/s10/v111/p2389142088.jpg)
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Then some with the ZBW1 filter attached to the front of the UV-LED light, all the first ones with 105mm f/4 AIS micro @ nominal f/8 mostly with PN-11 on unmodified D7100, 10-20 sec exposures.
Underside of a fern showing spore clusters (sori), UVIVF
#1
(http://otoien.zenfolio.com/img/s3/v44/p2389101373.jpg)
This one looks it is related to the Viola tricolor I am used to from Scandinavia, but bigger and cultivated,
Visual
#2
(http://otoien.zenfolio.com/img/s1/v49/p2389101365.jpg)
UVIVF:
#3
(http://otoien.zenfolio.com/img/s12/v181/p2389101414.jpg)
UVIVF side view reveals some "aliens" hiding inside the plant, one is about to emerge
#4
(http://otoien.zenfolio.com/img/s7/v167/p2389101422.jpg)
In UV-induced infrared flourescence (UVIIF) the cyan bright spots are not visible any longer:
#5
(http://otoien.zenfolio.com/img/s3/v8/p2389105330.jpg)
This one also appeared to be cultivated, visible light:
#6
(http://otoien.zenfolio.com/img/s1/v6/p2389101352.jpg)
UVIVF
#7
(http://otoien.zenfolio.com/img/s9/v92/p2389101377.jpg)
On the second day I had not planned anything and only brought the AW1 with me. The 11-27.5mm zoom is superb at the close limit and 27.5mm and f/6.3. The AW1 was just bracked on the desk as I do no have a tripod plate for it. These were actually better than the ones I did with the f/3.5 and f/2.8 versions of the 55mm Micro Nikkors, partly due to the resulting better depth of field. No L-37 filter used on the lens for these ones. The flower that was snatched from one of the flower beds at the university was white in visible light:
#8
(http://otoien.zenfolio.com/img/s7/v154/p2394676921.jpg)
UVIVF
#9
(http://otoien.zenfolio.com/img/s6/v136/p2389101434.jpg)
UVIF, There was a certain alien look to it (or perhaps belonging in a Harry Potter movie look) from the side. (anyone knows what it is?)
#10
(http://otoien.zenfolio.com/img/s6/v137/p2389101478.jpg)
[Perhaps this should have been a theme rather than in the gear talk?]
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Øivind, these are interesting images.
It should be safe to assume that the bright blue color indicates the UVIVF. On the other hand, the red petals might be the prove of some sort of visible light leak from the torch. Then the red leaves might show the UVIIRF (UV induced infrared fluorescence) of the chlorophyll?
https://en.wikipedia.org/wiki/Chlorophyll_fluorescence
But my last assumption may well be wrong, as I've heard that it is very tricky to capture the UVIIRF.
The protection filter on the front of my TK-566 is completely clear. I don't think it has any flitering effect on any specific wavelength.
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Thanks for your comments, Akira.
Interesting that your version of the Tank 007 LED light had clear glass in the front, in mine it definitely looks dark when not turned on and without the ZWB1 filter attached. This explains why my first attempts without the ZWB1 filter where not that different to the filtered ones. My supplier was ebay seller hkequipment.
The ball bearing test rendered bearings in ZWB1 filtered UV light black to the eye (only filtered by clear UV protection glasses) and also with my D40x IR-720nm body - hardly any specs visible at the distance used for the images. So it is safe to assume that the Tank 007 LED torch with the ZBW1 filter attached does not emit any significant amount in the visible light- or as shown here the IR spectrum (room light source left, filtered UV torch right - 20sec at ISO 100):
(http://otoien.zenfolio.com/img/s6/v144/p2395760694.jpg) (http://otoien.zenfolio.com/img/s3/v23/p2395760696.jpg)
Chlorophyll has a fluorescence that peaks in the red part of the spectrum and extends into the IR part. However since my D7100 is unmodified with its UVIR cut filter on the sensor intact, it is safe to assume that what it is picking up is the red part of the fluorescence. Of course frame #5 with the D40x IR-720nm might be picking up UV induced chlorophyll fluorescence in the IR part of the spectrum.
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Just checked out the TK-566 sold by hkequipment on eBay. The front protection glass indeed looks purple. But considering that we can "see" the purple color clearly, it is not an efficient UV-pass-VIS-cut filter.
As you would suspect, the purple color may indicate the visible light leaks in both of the blue and red ranges. I wonder if the deep red color of the petals and the leaves were lit by the leaked red portion? The UV-pass filters like Hoya U-330 and U-360 has the visible leaks in the very ranges.
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That is why to do the ball bearing test. Light leaks will show up as clear specks (directly reflecting the LED torch light leak). Without leaks the the ball bearings look all black. Of course it is possible that if I cranked the ISO all the way up and exposed at 30sec some specks would show up, but at the distances/ISO exposures used for these shots light leaks have negligible effects.
The exposures before I added ZWB1 filter to the Tank007 in the previous post is if of course an open question. However I think light from nearby fluorescencing objects was a bigger problem with my inexperienced attempts.
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Øivind, in fact I count on your scientific mind. I'm looking forward to you sharing your experience!