UV-Induced Infrared Fluorescence Investigation

[Andrea B.]

I don't understand why you do not get this.

 

The UV-Led outputs only UV and the tiniest bit of violet light which is easily suppressed using a 1mm U340 filter.

I am in total darkness so there is NO ambient Visible or Infrared light.

There is NO fluorescent Visible or Infrared light because Spectralon does not fluoresce.

So the only thing getting through that 715 IR-pass filter is Ultraviolet light. It is a "leaky" filter.

 

This outcome is repeatable by anyone who has the materials.

 

The fact that the 715 is a leaky filter is not important in ordinary sunlight photography.

It is important to UV-induced infrared photography.

[Cadmium]

It is not just the 715nm filter, all longpass filters willl do this, and many other filters, and many stacks also.

Even your Baader U + UV/IR-Cut stack that you mentioned above will show light if viewed directly.

Schott RG715 suppresses Visual and UV very strongly, it isn't "leaky". You may be jumping to a conclusion.

 

The only time I have seen PTFE not fluoresce was when Mark stacked added filters on the camera lens that blocked blue and upper red.

So I am not yet convinced that PTFE doesn't fluoresce in blue and red.

How does your Spectralon look in UVIVF? Gray? Or black? When illuminated with Nichia and U-340 2mm?

I would really like to see a test of that.

I am not saying it is fluorescing, I am just saying I don't believe it isn't, yet.

Show me.

[Cadmium]

I think what you are seeing when you directly view the RG fillers stacked on the front of the Nichia torch is fluorescing glass.

However, I don't think you are getting fluorescing illumination on your target/scene from the RG filters on your camera lens when you are illuminating the scene with the torch.

Can you show me a photo of your Spectralon in UVIVF using Nichia + U-340 2mm?

 

The Solarmeter 5.7 is the more sensitive model.

"1" is over limit, anything up to 1999 counts from right to left, anything exceeding the 1999 limit shows only "1" at the left.

Here is a test showing the amount of UV passing through RG715 2mm filter glass at extremely close range (right), and left is with no RG715.

[Cadmium]

If you believe that your original photos are recording reflected UV light which is getting through the RG filters on the camera lens,

then stacking a Baader U on the lens with the RG filter should theoretically not attenuate the reflected UV light entering the lens.

Does that sound correct to you?

A Baader U should transmit the UV light and not attenuate it, but it should attenuate anything in the visual and IR range.

You should give that a try, before you say "leaky" again. Let me know what you think. Maybe I "do not get this"?

If the RG715 + Baader U stack on the lens looks black, what does that mean?

So to answer your question on the first page again, "Do I need to stack a UV-Pass filter over my IR-Pass filters to determine whether they can pass UV?",

yes you do need to do that.

Oh, and I would still like a shot of your Spectralon disk in UVIVF.

[OlDoinyo]

If what you are seeing looks "dull red," then it is unlikely you are seeing UV or violet--there is no half-photon effect that can turn violet into red, and any light in the 400-nm range will excite two visual channels and certainly not appear just red. I would agree that this is likely to be red fluorescence.

 

In general, a black-IR filter is about as transparent to UV as a brick wall; I would not be surprised if the transmittance is below 10^-40.

[Andrea B.]

I promise I'll get back on this and provide some requested test shots !!!

Today I have to do some other stuff (like clean up the Thanksgiving kitchen!!!)

so I cannot spend time in the dark closet. :lol: :lol:

 

Thanks to Steve for all the input. And to Clark for the observation. B)

We will get this figured out.

[Andrea B.]

AHA !!!

Spectralon, which does not fluoresce, is so reflective that the Nichia 365nm UV-LED reflection back onto the filter can break the OD.

Ponder that for a moment......

 

 

Added later: Treat that as an hypothesis, please. Not as a statement of fact.

[Andrea B.]

Spectralon does not fluoresce. Here is a reference and a link. I've copied the relevant table and conclusion for you as screen shots.

 

However, apparently PTFE may or may not fluoresce depending on how it is treated, or not. The 2nd (and last) link is a reference for this.

 

---

Reflectivity Spectra for Commonly Used Reflectors

by Martin Janacek

Lawrence Berkeley National Laboratory, Berkeley, CA 94720 USA

Manuscript received September 23, 2011; revised December 14, 2011; accepted January 04, 2012.

IEEE Transactions on Nuclear Science Volume 59, Issue 3

This work was supported by the Director, Office of Science, Office of Biological and Environmental Research, Biological Systems Science Division of the U.S. Department of Energy under Contract No. DE-AC02- 05CH11231.

LINK to the downloadable PDF: Reflectivity spectra for commonly used reflectors - ‎Janecek

 

---

Screen shot: Table of tested reflectors from Janacek paper.

 

---

Screen shot: Results of reflector fluorescence testing from Janacek paper.

 

 

---

Here is a discussion of PTFE fluorescence when used as an integrating sphere liner.

LINK: https://www.research..._spheres_poster

[Andrea B.]

Oh, and I would still like a shot of your Spectralon disk in UVIVF.

 

Theoretically, how can I UVIVF photograph something which does not fluoresce visibly under black light? :D

 

Practically, however, it turns out that I can get something in a UVIVF photo of the set of Spectralon standards. Remember what I asked you to ponder above???? What I got in the UVIVF photo (tentative conclusion) is a very strong UV reflection back onto my UV/IR blocker which broke its OD and recorded some light reflecting off the 99% standard.

 

Subject: I set up the 5 Spectralon standards against a black gear case which does not fluoresce. Then I added to the set up the recently acquired UV Innovations^TM Target UV (UVA Version 1.1) fluorescent patch strip. I used the Low/Medium fluorescent side.

 

Camera + Lens + Filter: D610-conversion + UV-Nikkor 105/4.5 + Baader UV/IR-Cut Filter.

Flashlight: 365nm UV-LED Nichia + KolariU (very unleaky this one is)

 

Procedure: At f/4 and ISO-400, I set exposure time so that the fluorescence strip was not blown out. That makes a proper Low/Medium fluorescence shot. Here it is. No edits except for proper white balance/colour. (I ran out of time.)

 

UVIVF

 

Visible Flash Reference (B&W)

Notice how my poor dark grey standard has deteriorated. :(

[Cadmium]

A picture is worth a thousand and words, as they say.

If your Spectralon is black in UVIVF then I might consider that it might not fluoresce in UVIIRF also.

However I am fairly certain that what you have photographed in the these original shots is not reflected UV.

It is probably in the red to IR range, and I am not ruling out fluorescence. It could be fluorescing for the same reason the bricks are. If they are.

 

The photo was not here before.

 

You know... I think it is because we were posting at about the same time...maybe.

[Andrea B.]

Do kindly observe that I provided a link in Post #33 to a paper in which Spectralon was tested for fluorescence and found not to have any.

Spectralon does not fluoresce. PTFE might fluoresce depending on treatment. So whatever treatment (sintering, baking, and so forth) Labsphere gives PTFE to produce Spectralon kills all possible fluorescence.

 

The white Spectralon standard is reflecting back in the direction of the lens & filters approximately 98% of the UV light shined upon it. That is somewhat like directly shining the torch onto the lens & filters. Except that the torch has a directed beam and the reflection off the Spectralon is diffuse and no longer a directed beam. Still, there is a heck of a LOT of reflected UV light off that Spectralon thingie.

 

I must let this rest now while everyone thinks it over. I have to do some other stuff for awhile.tl

 

I also need to mention that while making the photograph and directly looking at the Spectralon scene, the only thing I can see is the fluorescence off the strip and a kind of very very dull dark purple-black "look" to the white disc.

[Cadmium]

I didn't see your Spectralon test pics here when I posted my last post, don't know why.

Regardless of the link about Spectralon not fluorescing, some of your whiter samples are fluorescing, for whatever reason. Dirt?

The addition of the INNOVATIONS strip is nice, however it defines the exposure, thus making the Spectralon look darker than they might otherwise.

You might actually want to put the strip in a UVIIRF shot set up the same as your original shots using the Spectralon disk and the bricks.

 

Are you still saying:

"Remember what I asked you to ponder above???? What I got in the UVIVF photo (tentative conclusion) is a very strong UV reflection back onto my UV/IR blocker which broke its OD and recorded some light reflecting off the 99% standard."

 

Did you try the test I suggested yet? Stacking your Baader U on the RG715 (or other RG IR filters) to see what the 30 second photo looks like then?

You should try that. It will look black, and that is because there is no UV transmitting through the RG715.

Your photos are not reflected UV transmitting through the IR filters.

So far everything you have shown seems to indicate that your Spectralon is fluorescing. Your white Spectralon looks identical to my PTFE in UVIVF.

The only other idea I have is that there is reflected IR in your UVIIRF shots (could there be any Red/IR from the Nichia?).

You might try adding S8612 3.5mm on the front of the U-340 2mm filtered torch (in your case U-340 1mm), this will remove as much red/IR as possible (if there is any red/IR at all transmitted via the Nichia/U-340),

that would help define what range is being excited or reflected, given the RG715 is pretty close to visual, and thus contains some 'false' color,

but all of your IR filters are showing basically the same thing, just slightly different color cast.

 

I would like to see you post a shot exactly the same as one of your original pictures, same lighting, same exposure, same torch/LED, same filter on the torch, same filter on the lens

with the addition of the Baader U on the camera lens also. Maybe I still "do not get this", but have you tried the addition of the Baader U yet?

[Cadmium]

Dig out your camera, and give this a try your self.

What you are getting is not UV reflected light, you are getting infrared fluorescence from that Spectralon disk. and your bricks too.

 

 

Here is another example with more things tossed into the scene.

Note the S8612 3.5mm, which is transparent to UV, but blocks red/IR, the PTFE under it is fluorescing IR, but that IR light can not pass through the S8612 to the camera lens.

The U-340 passes UV, which fluoresces the felt under it, but the IR fluorescence isn't passing through the U-340, which leads me to believe that the fluorescence is mostly above the 700nm or even 800nm range maybe,

I see a little more light coming from the U-340 2mm, maybe, than the S8612 3.5mm, but we are definitely not seeing any reflected UV.

Everything you see in the photo below and the original photos you posted is UV induced IR fluorescence. That's all there is too it, problem solved, go clean your Spectralon if you want?

[Andrea B.]

Steve you are overwhelming me a bit here! I need some time to catch up. I am going to try to replicate your tests as I get time. It would help if you carefully listed the requested tests so I can work through them systematically and don't have to go back through 38 posts to dig them out. :)

 

Here at UVP World Headquarters I occupy many positions auxiliary to the UVP Owner/Admin slot. B) For example, today I must don my Holiday Decorator hat and pack away the Thanksgiving items and haul out the Christmas trinkets to begin that. Where I live it is tradition to place a small (electric) candlestick in each window during the dark winter months. Whatever one celebrates at the Solstice, this is a nice tradition and we enjoy it.

 

Replication of results and re-testing is important part of the scientific method, so I fully support all this and will totally keep working on it. This has turned into an ALL-TIME-GREAT-THREAD !!!!!!!!!!!!!

 

---

 

The addition of the INNOVATIONS strip is nice, however it defines the exposure, thus making the Spectralon look darker than they might otherwise.

 

Response regarding Target-UV fluorescence strip: The primary purpose of this strip is to test how strong is a subject's fluorescence by comparing it to the target strip's fluorescence. How the baseline of low/medium/high fluorescence is determined, I'm not sure. This is from some standard that I do not know about. But anyway, keeping in mind that one can force light thru almost any filter, it is important to place some controls on the fluorescence photograph so that we can determine whether unwanted light leaks (if any) and unwanted reflections (if any) are significant or not. All photographs will look brighter if exposures are longer. So we have to ask what is the sensible exposure for a particular case? For fluorescence experiments I would suggest that the Target-UV strip is the right thing.

 

---

 

Before listing the potential experiments, we need some baseline gear.

Torch: Nichia 365nm UV-LED

Base Torch Filter: Some filter which prevents violet/visible leakage. What filter shall I use for this?

Lens: UV-Nikkor 105/4.5

Base Lens Filter: Schott 715nm (2mm) because we are trying to determine something about

Camera: D610-broadband

Fluorescence Standard: Innovations Target-UV

Reflective Standard: Labsphere Spectralon discs

 

GOAL: what the heck was the original goal when I began doing all this...... :P :P :P :P :P :P :P :P :P :P :P

 

---

 

I think I need to stop this thread and start a new one. Everyone OK with that?????

[bobfriedman]

are we taking our ball and going home?.. how about using some BG glass to test it.

[Andrea B.]

no no no. I want a clean start with neatly defined experimental goals.

This thread started with what I thought as a anomalous outcome. Then we had many other observations. So in order to clarify things, I need to start over and REPEAT the existing experiments and carefully step through wnat needs to be done. (or not).

 

SEE NEXT POST.

 

P.S. I can't go home. I am home. :lol: :lol:

[Andrea B.]

[Last Update: 27 Nov 2017 10:24 GMT -5] Edited Goal and Experiment statements for clarity.

 

GEAR

 

Camera: D610-broadband

 

Lens: UV-Nikkor 105/4.5

Lens Filter (Excitation Filter): As needed per individual experiment

 

Torch: Nichia NCSU033A 365nm UV-LED

Base Torch Filter (Emission Filter): Hoya U-340 (rmm). Any violet/blue leak will be blocked.

 

 

FILTERS

 

IR-Block Filters:

• Baader UV/IR-Cut
  
• Schott S8612 UV+Vis-Pass (various thicknesses)
  

IR-LongPass Filters:

• Brand (thickness) Designation: trans begins/30%/60%/maximum
  
• Schott (2mm) RG 715 IR+Red-Pass: 690/713/727/770nm
  
• Schott (2mm) RG 780 IR-Pass: 730/768/782/840
  
• Schott (2mm) RG 830 IR-Pass: 750/817/833/885
  

IR-BandPass Filters:

• MaxMax BPG 795-860nm IR-BandPass
  
• MaxMax BPR 921-958 IR-BandPass
  

UV-Block Filters:

• Baader UV/IR-Cut
  

UV-Pass Filters:

• BaaderU: 350fwhm60, 78% trans at peak.
  
• KolariU: 365fwhm40, 50% trans at peak.
  
• LaLaU: 363fwhm, 65% trans at peak.
  
• StraightEdgeU: 379fwhm52, 80-89% trans at peak interval 360-385 nm
  

 

STANDARDS

 

UVI Visible Fluorescence Standard: UV Innovations Target-UV^TM

UV/Vis/IR Reflective Standard: Labsphere Spectralon® discs, PTFE disc

 

UV-Induced Visible Fluorescence Subject: UV Innovations Target-UV^TM

UV-Induced Infrared Fluorescence Subject: Green Leaves, (Synthetic Ruby?), (Synthetic Emerald?)

Note: I propose to use a clipping from my Asparagus Fern, Asparagus densiflorus 'Sprengeri'.

 

OTHER

 

Ambient Light: None. Please assume that all photographs made during these experiments are made in the dark. Lights are turned off. Curtains are closed. All appliance mini-lights are covered.

 

Fixed Exposure Settings: f/4.5 @ ISO-800.

 

Still Life: For each experiment set up a still life which contains the Labsphere 99/50/2% reflective disks, the PTFE disk, the Target-UV strip and some green leaves from the Asparagus Fern. Make a Visible Flash photo to reference the set-up.

 

Acronyms:

IR = infrared

UV = ultraviolet

UVI = ultraviolet induced

UV/IR = ultraviolet or infrared

UV/Vis = ultraviolet or visible

PTFE = polytetrafluoroethylene

 

---

 

GOAL ONE

Investigate visible fluorescence of Spectralon® and PTFE. Do these materials visibly fluoresce under UV illumination? And, when used for UVI Visible fluorescence photography, does the Baader UV/IR-Cut filter on the lens pass any UV from the torch illumination?

 

Notes:

1) The specific treatment used to produce my PTFE disk is not known.

2) As per Labsphere's website, Spectralon® can reflect and transmit but it cannot absorb.

See section 2.3, page 8 in Tech Guide: Reflectance Materials and Coatings

3) Spectralon® does not fluoresce. See PDF: Reflectivity spectra for commonly used reflectors.

 

Goal One Experiment 1: See Post #46

Make UVI Visible photographs of the still life. Test for UV leakage by the Baader UV/IR-Cut filter.

 

Note: A 'forced exposure' is one having an exposure time much longer than what might reasonably be expected under the given illumination. Because there is no UVI infrared standard by which to estimate exposure time in UVI infrared photographs, I have arbitrarily chosen exposure times of 15" and 30".

• Make Visible reference photo, if needed.
  

• Make a UV-induced visible fluorescence photo under filtered UV-Led Torch illumination with the Baader UV/IR-Cut filter on the lens. Determine exposure time using the Low/Medium side of the Target-UV strip.
  

• Stack the BaaderU UV-Pass filter onto the UV/IR-Cut filter. Shoot at the same exposure as before. Then make forced exposures to force UV light leak (if any).
  

---

 

GOAL TWO

Investigate infrared fluorescence of Spectralon® and PTFE. Do these materials fluoresce in infrared under UV illumination? And, when used for UVI infrared fluorescence photography, do the Schott RG 715/780/830 (2mm) filters on the lens pass any UV from the torch illumination?

 

Goal Two Experiment 1: See Post #51

Make UVI infrared photographs of the still life. Test for UV and UV/Vis leakage by the IR-pass filters.

 

Note: A 'forced exposure' is one having an exposure time much longer than what might reasonably be expected under the given illumination. Because there is no UVI infrared standard by which to estimate exposure time in UVI infrared photographs, I have arbitrarily chosen exposure times of 15" and 30".

• Make Visible reference photo, if needed.
  

• Make a UV-induced infrared fluorescence photo under filtered UV-Led Torch illumination with the Schott RG 715/780 (2mm) on the lens.
  

• Stack the BaaderU UV-Pass filter onto the RG filter. Shoot at the ordinary exposures. Then make forced exposures to force UV light leak (if any). Note that the transmittance charts for the Schott RG filters do not indicate UV light transmission for 2mm thicknesses.
  

• Stack the Schott S8612 (3.5mm) onto the RG filter. Shoot at the ordinary exposures. Then make forced exposures to force UV/Visual light leak (if any).
  

Goal Two Experiment 2: See Post #xx

Revisit the initial UVI infrared photographs of Spectralon 99% reflective disk on bricks and try to find the source of the apparent infrared fluorescence. Use Schott RG 715 (2mm) IR-pass filter.

• Shoot forced exposure of disk against dark background.
  
• Shoot forced exposure bricks (no disk).
  
• Shoot forced exposure of disk against bricks.
  

[Andrea B.]

Don't forget to look at preceding post.

 

The reason I need to stop this thread and restart it as Part Two is that when the topics become long like this one is, it is hard on the server and also difficult for folks with slow internet to load the whole thing, OK?? Gotta think of that stuff as Owner/Admin. B)

UVP only has the cheap-o server package because we are a tiny little specialized forum with minimal daily traffic. If I ever need to, I will of course upgrade the server package.

Everyone is free to add some more suggestions here so that I can properly write them up. But I'm going to post experimental outcomes to a new topic.

 

OK, nobody wants me to split this thread, so I won't.

[Cadmium]

I vote no on ending the topic. Lets keep this all together. I see many other topics on here that go on for page after page. This is not a problem at all.

This topic and your questions are interesting, and I have spent some time and thought pondering and testing your questions.

So lets not throw the baby out with the bathwater.

 

The question so far is, what light are we seeing in your photo tests?

1) reflected UV passing through an IR filter?

2) reflected IR?

3) IR fluorescence induced by UV?

 

We could list a few more combinations, but I would like to move forward with a conclusion about the IR pass filters,

and agree about what is passing through the IR pass filters, then we can get on the same path.

Please keep the topic running, you and I and others can add anything when wanted.

 

Steve you are overwhelming me a bit here! I need some time to catch up. I am going to try to replicate your tests as I get time. It would help if you carefully listed the requested tests so I can work through them systematically and don't have to go back through 38 posts to dig them out. :)

 

This is very good, lets do that, when you have time, no rush.

Right now I have proven to myself that there is no reflected UV passing through the IR pass filters, if you would perform the test I suggest, then we can ponder the results.

 

Bob has an excellent second test idea, although I will change the BG38 to S8612 3.5mm (you and I both have that also), and I have just now tried it myself.

 

Looking at your second group of tests where you have the U-340 on the torch, I would suggest the RG715, or higher,

I see light even with the RG830 tests, so take your pick.

 

1) Choose one or more IR pass filters for the lens

2) Shoot the same exact test you did before, all the same equipment, same setting, exposure...

3) Then add your Baader U on the front of the IR pass filter, and shoot the same shot again, same setting, etc..

4) Now remove the Baader U and replace it with the S8612 3.5mm on the front of the IR pass filter and shoot the same shot again, same setting, etc..

 

This will give you three photos,

1) one photo will only be filtered by the IR pass filter, and it will transmit everything above the cut off point of that filter.

2) the second photo will be with the IR longpass filter and the Baader U added on the front, which will pass only UV to the IR pass filter, and the IR pass filter will pass any UV it can to the camera.

3) the third photo passed UV and Visual to the IR pass filter via the S8612 3.5mm, and the IR pass filter will pass any UV and any Visual it can to the camera.

 

I will wait patiently, whenever you get around to it.

[Andrea B.]

Before doing anything else I need to settle on what filtration should be used on the torch to cut any possible violet/blue leak?

 

I have U-340 (4mm) and U-340-1mm and the named filters (BaaderU, KolariU, LaLaU, StraightEdgeU).

Do we have a chart for U-340 (4mm) anywhere?

 

LATER: Ok, no answer, so I have chosen to use the U-340 (4mm). Cuts trans of UV a bit, but will certainly also totally cut violet & blue leakage from the UV-Led if there is any. :D

[Andrea B.]

Last Update: 27 Nov 2017 10:37 GMT-4: Added goal statement. Clarified experiment statement.

 

GOAL ONE

Investigate visible fluorescence of Spectralon® and PTFE. Do these materials visibly fluoresce under UV illumination? And, when used for UVI Visible fluorescence photography, does the Baader UV/IR-Cut filter on the lens pass any UV from the torch illumination?

 

Goal One Experiment 1

Make UVI Visible photographs of the still life. Test for UV leakage by the Baader UV/IR-Cut filter.

 

Note: A 'forced exposure' is one having an exposure time much longer than what might reasonably be expected under the given illumination. Because there is no UVI infrared standard by which to estimate exposure time in UVI infrared photographs, I have arbitrarily chosen exposure times of 15" and 30".

• Make Visible reference photo, if needed.
  

• Make a UV-induced visible fluorescence photo under filtered UV-Led Torch illumination with the Baader UV/IR-Cut filter on the lens. Determine exposure time using the Low/Medium side of the Target-UV strip.
  

• Stack the BaaderU UV-Pass filter onto the UV/IR-Cut filter. Shoot at the same exposure as before. Then make forced exposures to force UV light leak (if any).
  

---

 

Visible Reference Photo

The JPG was extracted from the raw file in Photo Mechanic. No edits were applied.

 

UV-Induced Visible Fluorescence Photos

White balance, colour profile and minor highlight recovery were applied in Photo Ninja. Oversaturated red patches were slightly desatted in Capture NX2 using a colour point saturation slider. Those Target-UV red patches are really red when fluorescing.

Naturally the unfiltered UV-Led torch provides a faster exposure (first photo here) than does the torch filtered with 4mm of Hoya U-340 glass (2nd & 3rd photos). But we sensibly wanted to ensure there was no violet or blue leak from the UV-Led.

Viewers may decide for themselves whether or not they see Visible fluorescence by the Spectralon or PTFE disks!

Here I aimed the torch at a angle underneath the leaves.

 

UV-Leak Test Photos

The Baader UV/IR-Cut filter does not seem to leak UV under illumination from a 365nm UV-Led torch filtered with Hoya U-340 (4mm) at a normal exposure nor under forced long exposures.

[Andrea B.]

The labels are incomplete on the last 3 photos. Fixing that now.

[Cadmium]

Before doing anything else I need to settle on what filtration should be used on the torch to cut any possible violet/blue leak?

 

I have U-340 (4mm) and U-340-1mm and the named filters (BaaderU, KolariU, LaLaU, StraightEdgeU).

Do we have a chart for U-340 (4mm) anywhere?

 

LATER: Ok, no answer, so I have chosen to use the U-340 (4mm). Cuts trans of UV a bit, but will certainly also totally cut violet & blue leakage from the UV-Led if there is any. :D

 

I use U-340 2mm. Your U340 1mm seems to work, but the 2mm is a little better assurance that any possible blue leak from the Nichia will be cut off.

U-340 4mm seems a little too thick for that job, because it will reduce peak 365nm peak % amplitude, thereby reducing the power of the torch light.

UG11 is the best replacement for U-340, so you can stack those two glass types together to get another thickness.

2mm would be ideal, because it would be more standard with what other people are using. I think Mark used U-340 2mm.

I posted a chart of that here, let me go find it.

 

Here is is, sorry this one doesn't show 1mm plot..

http://www.ultraviol...dpost__p__17945

[Cadmium]

As a test. I think if I were trying to remove reflected UV from entering the camera lens I would use a GG435, usually I just use GG420, but you can go higher if you want, but then you are filtering out blue light from fluorescence too.

Mark used a similar yellow/green filter (?) to cut blue, most of the 400nm range, I think.

But this is a good test.

I have been told hat Baader UV/IR-Cut leaks some UV slightly below 400nm, but your torch is filtered with the U-340 4mm filter, so that should be removing UV a littler lower nm than the 2mm does.

[Cadmium]

What is the larger round disk at the top?

OK, I guess that is PTFE.