Spectralon fluorescence?

[Andrea B.]

Any PTFE or Spectralon "fresh out of the box" will fluoresce from its manufacturing impurities unless it has been treated to remove/lessen those manufacturing impurities. I've said that multiple times. That's why LabSphere (and other plastics companies who make optical gear) have higher grades of this stuff for use in integrating spheres where UV light will be used.

---

 

I tried setting the Convoy face down on my Spectralon-99 but got nothing. However, before everyone throws up their hands in horror that I could not get fluorescence , let me reassure you that I will try this again. Maybe I had the angle wrong. Maybe I had the distance wrong. I dunno. I'm trying to reproduce this. I will keep trying.

 

Camera: Nikon Z7

Lens: 24-70/4.0S with no filter

Flashlight: Convoy S2+ with U-340 filter

 

 

Visible reference

This photo was white balanced on the Spectralon and cropped in Photo Ninja.

That thing was clean when I put it down.

Didn't take very long for the cat hair to float in. My goodness. (Disgustarito.)

f/8 for 3" @ ISO-400

 

UVIVF

This photo was cropped in Photo Ninja.

f/8 for 30" @ ISO-400

There is a very tiny sliver of blue??

[Andy Perrin]

Andrea - try putting a piece of aluminum foil under the PTFE if it's thin enough that you think light might make it all the way through. That will reflect the remaining UV back, so you would get more fluoresce if there is any to be seen.

[Andrea B.]

OK.

[Andrea B.]

well, Andy....the spectralon standard is in a Delrin container, so I don't think the underlying foil will change anything.

 

If you push that frame, then you can see the flashlight in there. And some light from somewhere. (argh!)

Here is the UVIVF frame with the Photo Ninja Illumination slider pushed all the way to 50.

[Andy Perrin]

It does look like it might be fluorescing under there, but you have some kind of background light here, so I think that anything that's diffusing is too faint to be seen. One thing that does seem clear to me is that whatever is fluorescing is MUCH fainter than with Cadmium's example. I wonder if you have less of whatever the mysterious manufacturing contaminants are?

[Andrea B.]

Yes, I'll try a better darkroom. It did not seem like there were any apparent leaks, but 30 seconds will bring out light leaks.

Amendment: Actually 30" did not bring out the light leak. It was the Illumination slider pushed to the extreme which brought out the light leak across the top of the frame. The top of the door probably does not fit tightly enough.

[Andrea B.]

This lovely abstraction was made by me trying to hold the Convoy over the Spectralon disc for 5" with one hand and hold the camera steady with the other. :lol: Dream on, silly lady.

It's time to pack it in for the night.

 

f/8 for 5" @ ISO-400

Dust motes courtesy of New Mexico's very dry air.

The whitish patch on the left is some Velcro® on the bottom of the container.

It's really kinda dark in the center. Looks that way too with the "naked eye".

[Cadmium]

I am going to leave this topic again.

I am not here to get anyone upset, or to argue, and I don't want to get in trouble or get anyone mad at me.

Like I said, I can't think of anything else to test except a new sample of whatever, and I don't think I will invest in that right now.

Enjoy.

[Andrea B.]

Cadmium, none of this is about you, so don't worry. Nobody is arguing. We are all just trying to figure it out.

 

I'm just working to try to reproduce fluorescence results with my standard. Andy suggested my exposure times were not long enough and suggested that I try the Convoy face down on the Spectralon. I agreed and wanted to make those suggested shots. But my results were not good as you can see above. I had a light leak and I maybe shot at a bad angle. So I have to try again.

 

I have no idea why my Spectralon is not as fluorescent as some of the others. Maybe it was a different batch from the olden days when I bought it in 2012. Maybe it was higher grade because it was calibrated. I just don't know.

 

Tomorrow is another day.......

[Andy Perrin]

Andrea, all that blue light has gotta be fluorescence of something.

 

P.S. This is what your hand was doing:

[Andrea B.]

That is so awful! Whyever do we think we can hold still for 5"? Well, maybe some of you all can, I sure can't.

 

In the pure dark I always kind of lose my balance. Do you?

[Andy Perrin]

I can if I have something to stabilize against, but definitely not in the air like that. Like, if I have a monopod or a wall to lean my hand on, it definitely helps.

 

Oh well, we will await further experiments when you have time, but I think what you've done so far has been enough to show yours fluoresces less than Cadmium's, but I think still a bit.

[DaveO]

Way back in 1959 there was an article about Atmospheric dust and fluorescence

 

atmospheric dust and fluorescence

https://www.nature.com/articles/1831048a0

 

and in 2017 another about Fluorescence detection of protein content in house dust

https://pubmed.ncbi.nlm.nih.gov/27538819/

 

Dave