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Red Seaweed UVF

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#1 Adrian

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Posted 22 January 2018 - 09:42

I read recently that red seaweed (Red Algae: Class Rhodophyceae) fluoresce in UV. They contain chlorophyll which is masked by the red pigment phycoerythrin. Apparently the pigments are being used by researchers to tag antibodies to study their effect on tumour cells.

On a visit to the seaside yesterday I collected a small bag of red algae, and examined it under UV as soon as I got home. The result is a very beautiful orange fluorescence. I think (though identification can be very difficult with partial specimens) they are primarily the species Dulse: Rhodymenia palmata.

Technical specs: UV source: Convoy LED torch. UVF exposure 20 seconds @ f/11, specimen "painted" with light.

Hopefully I will get the chance to do some more images with better specimens during the year.

Attached Images

  • Attached Image: red seaweed UVF lo res.jpg


#2 Mark

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Posted 22 January 2018 - 16:03

Hi Adrian,

I'm a little unclear about just what this is. When you say UV fluorescence, do you mean UV induced fluorescence? Could you include which filters you used on the camera/light source?

#3 Andy Perrin

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Posted 22 January 2018 - 16:06

The photos are quite amazing.

#4 Adrian

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Posted 22 January 2018 - 16:12

Yes, sorry, UV induced fluorescence. The weed was illuminated in a completely dark room with a Convoy UV S2+ LED torch (365nm). I used a long exposure during which time I "painted" the subject with the light from the source, ensuring as even a light as possible on the weed. No other filters used.

#5 Andrea B.

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Posted 22 January 2018 - 18:20

That is really beautiful! Thanks for posting.

I must try this myself next summer when I have access to seaweed samples.

It is necessary to mention both the barrier (lens) filter and the illumination filter when posting examples of UV-induced Visible fluorescence. That way all viewers are sure of what is being shown. For example, some subjects also emit fluorescence in the Infrared region when bathed with UV light.
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#6 Hornblende

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Posted 22 January 2018 - 18:29

View PostAndrea B., on 22 January 2018 - 18:20, said:

For example, some subjects also emit fluorescence in the Infrared region when bathed with UV light.

Has anyone ever try to record a "full spectrum" fluorescence? I always use a Baader UV/IR cut filter for my UVIVF shots, now I wonder how the image would turn out if I don't use the filter and let the camera record VIS + IR fluorescence.

Edited by Hornblende, 22 January 2018 - 18:30.


#7 Andy Perrin

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Posted 22 January 2018 - 18:35

Hornblende, how would that work? The camera would record the UV that is stimulating the fluorescence, wouldn't it?

#8 Hornblende

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Posted 22 January 2018 - 18:42

Yes you are right. In this case a GG420 filter should be in front of the lens. I don't have one and I don't really have enough money to invest in filters right now, maybe Mark can try someday? :)

Edited by Hornblende, 22 January 2018 - 18:46.


#9 Andrea B.

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Posted 22 January 2018 - 19:20

Methinks nothing set up to be "full spectrum" ever really is. :D For example, if we shoot a converted camera with no filter on a broadband lens, we record mostly Infrared with some Visible and almost no UV. The IR overwhelms.

However, this kind of thing always need proving, so your suggested experiment is a good one. What would happen when shooting in the dark under UV illumination with NO ambient light leakage and a subject which fluoresces both in Visible and IR? Could be interesting!

Let's list some barrier filters to try in an experiment (whenever one of us can get-a-round-tuit):
  • Baader UVIR-Cut for Vis fluor only
  • Schott 850 for IR fluor only (maybe the 830 instead?)
  • Hoya R72 or Schott RG9 for just a twinge of red and mostly IR.
  • BaaderU for UV only (as a reference)
  • StraightEdgeU for "high" UV only (as a reference)
  • Schott GG420 for Vis + IR (filter fluoresces so take care)
  • Schott S8612 for UV + Vis
  • and, finally, the No Filter B)
Suggestions welcomed.


EDIT: changed BG-39 to S8612.
Andrea G. Blum
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#10 Mark

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Posted 23 January 2018 - 00:28

I can certainly execute this experiment - but not until this weekend (just have too much going on in the interim). The only suggestion I might may so far is to use an R72 for the UVIIF capture, as I've already found from head-to-head tests that IR fluorescence (at least, UV induced) does not extend very far into NIR (cutting on at 830+nm results is very weak to no signal at all). I'm open to suggestions for a test subject... (I'm considering a sapling I currently have hanging on indoors, just waiting for some good spring sunshine). Maybe a food/edible? Other?

#11 Andy Perrin

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Posted 23 January 2018 - 01:13

Lentils have crazy bright UVIVF...

#12 Mark

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Posted 23 January 2018 - 02:22

Come on Andy! Now you have to post a pic!... (because I don't have any lentils on-hand :))

Edited by Mark, 23 January 2018 - 02:22.


#13 Andrea B.

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Posted 23 January 2018 - 03:22

Not sure about R720 for IR fluor because that's going to let a bit of Vis red through? Not enough to worry about? :)
But will add it to list.
Andrea G. Blum
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#14 Andy Perrin

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Posted 23 January 2018 - 05:04

View PostMark, on 23 January 2018 - 02:22, said:

Come on Andy! Now you have to post a pic!... (because I don't have any lentils on-hand :))
Well OKAYYYYY...

Rush job for speedy delivery!
Hoya UVIR cut on Sony 50-200mm lens, F9, 6"
UG11 2mm on Convoy S2+, held on with fingers
Attached Image: Lentils UVIVF Flashlight HoyaUVIRcut Sony 52-200mm f9 1%22 iso100 UVP.jpg
Attached Image: Lentils UVIVF Convoy S2+ HoyaUVIRcut Sony 52-200mm f9 6%22 iso100 UVP.jpg

Obviously a lot of blue fluorescence from the cutting board, sorry about that. Actually this is pretty weak considering the intense glow I have seen from lentil soup.

Edited by Andy Perrin, 23 January 2018 - 05:43.


#15 Andrea B.

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Posted 23 January 2018 - 15:10

Dave postulated a blue lignin fluorescence in one of his recent UV-signatures. Probably what the cutting board is showing? I rather like its blue glow as a background to the lentils.
Andrea G. Blum
Often found hanging out with flowers & bees.