UV Induced Infrared Fluorescence 2

[nfoto]

A Baader UV/IR cut filter over the lens plus a 2E or similar would be a safe way towards the end outlined by Steve.

[Cadmium]

The only thing I can question is the need for the UV/IR-Cut (or BG) given the example shown by Pylon (bottom two pics)

But that is how I do it, visual filter + 2E (or other).

 

https://www.ultravio...-1446255154.jpg

[JMC]

Steve, This highlights the challenge of describing a method for fluorescence.

 

Yes I get that in your example you need a U-340 on the flash, I'm not saying that you don't need a U filter.

 

What I was saying is that for UVIVF using a flash you'd only need to block the IR from the flash, if you had a camera which had been modified to image the UV-Vis-IR region. If you have an unmodified camera, I don't understand why there is a need to block the IR from the flash. Unless that is the internal filter stack of the camera is not sufficient to block the IR from the flash. Is that the case?

 

Hopefully that make sense now.

[Stefano]

I think it is a layer of safety. In theory you are right, but if the transmission of the camera filter overlaps a bit with the transmission of the U glass (alone) on the flash, you have a problem.

 

To summarize what Steve said, you need to work in "sealed compartments". Make the flash emit only what you want and make the camera see only what you want, without overlaps. In UVIVF you don't have to block all IR coming from a flash as long as you put at the same time an IR-cut filter on the lens, since this way IR won't contaminate your image, unless you have an anti-stokes shift going on, and that's not the case in probably 99.99% of stuff (but, anyway, you always have to block IR entering the camera, as UVIIRF can contaminate UVIVF images, just to stay safe).

 

ZWB1/U-340/UG11 leak before ZWB2/U-360/UG1, their red/IR bump is shifted towards shorter wavelengths, they leak before 700 nm, if thin I think even at 650 nm. This means that you would need more S8612 to block their leak, and that means even less red.

[bvf]

Wow, what a mass of input and comment to wake up to on a Sunday morning! I appreciate people’s time in providing information and advice.

 

Here’s my summary of what has been said, and my thoughts in response.

 

1. Use U340 & S8612 (or 4.5 mm BG40) on the flash

 

The reason I won’t do this is simply down to cost. I use 4 flashguns, so I would need four 5x5 cm squares of both filters, so we’re probably talking about $500. At the moment, fluorescence is a hobby project for me, so spending that much on filters is a bit steep. If I get hooked on fluorescence, I may be prepared to make the investment.

 

So for now, if I use flash it will have to be with ZWB1 on the flash and possible an S8612 on the camera.

 

I do not use flash for IRF because the IR leakage is too high. I only use it for UVIVF. And for this I use an unmodified camera, so the problem of IR leakage is greatly reduced. If I think I may be getting far-red or IR leakage then I can use the S8612 on the camera. But I’d prefer not to use the S8612 because it depresses red fluorescence considerably – and I don’t know what WB standard I could use to address this.

 

2. On a torch, use a U340 (don’t need S8612)

 

A “Nemo” torch is what I use generally for UVIVF and always for UVIIRF. This has a UV-pass filter built in: I don’t know what type, probably ZWB1.

 

I can easily use a U340 (and even in combination with an S8612) with this. My initial results using a Baader U and S8612 don’t see any difference when adding these filters, but I’ll continue to do some comparative tests to see if I can see any difference when using these or a U340.

 

3. For IRF, use a LP IR filter on the camera to block visual light.

 

I’m combining IRF with tri-colour IR, so rather than making a single exposure with a LP IR filter I’m making three exposures with IR bandpass filters – so visual light is being blocked.

 

 

4. IRF: you don’t get colour unless you use a lower longpass filter or no filter at all (=false colour)

 

I understand this to mean colour provided by the camera in a single exposure. As I say above, I’m looking to get colour in IRF through the three tri-colour exposures.

 

5. For UVIVF, block fluorescence above visual (e.g. by using a BG40, UV/IR cut) – not needed for a stock camera

 

I use a stock camera for UVIVF.

 

6. “from what I have read Bernard say in this topic so far, it doesn't sound like he is doing UVIIRF exactly correctly”

 

Certainly true if I was using flash – but I’ve abandoned this because of the highly obvious IR leakage.

 

The comment only partially applies to using the Nemo. I think the only possible question is whether to add a U340 to the Nemo or just use its inbuilt filter. I have tried using a Baader rather than U340 and not noticed any difference. But as mentioned above, I’ll do some more work on whether this makes a difference.

 

7. “If the exposure time of UVIIRF is not long then you are probably not doing it right.”

 

Agreed. Whereas UVIVF exposure using the Nemo may be 15 seconds at ISO 100, I’m having to use 50-100 minutes for the 1000 nm exposure in the UVIIRF tri-colour set. (I’m lying, of course – I don’t paint with the torch for an hour, I step up the ISO to reduce the exposure time.)

 

8. … we are not all scientists here trying to prove that 385nm excitation of flower A leads to 850nm emmission on pollination day Q … If it looks artistically good to you and you have a vision for that subject, than by all means hit it with UV and 5% IR to get a blue background in your subject with a Red pop fluorescence. … Sometimes we get too technical here ... Some subject have interesting colours mixed in with various leaks. Just don't claim anything, and your fine. If you want to make a claim to a specific subject doing something, than you need to be throw with all your controls for each subject, every single time you image it.”

 

I think there’s a lot of sense in this comment. I don’t have access to the resources that some other members have and am not striving for scientific purity. I’m interested in seeing what happens in different scenarios, and perhaps capturing types of image that other people haven’t.

 

It doesn’t worry me too much if I have a bit of impurity in the image as long as it substantially represents what I am after.

 

But that also means that I mustn’t claim a level of scientific rigour that I’m not achieving.

 

9. “A Baader UV/IR cut filter over the lens plus a 2E or similar would be a safe way towards the end outlined by Steve.”

 

Following a thread elsewhere, I have obtained a 2A filter. But haven’t found a 2E at a price I’m willing to afford.

 

I may well get a Baader UV/IR cut filter. I make a lot of use of my current unbranded UV/IR cut filter (bought from the person who did my full spectrum conversion). Even if this has the characteristics of the Hoya UV/IR cut filter, then it is still passing 26% at 700 nm and 2.5% at 720 nm. The Baader looks like it is down to 1-2% by 700 nm.

 

PS: looks like the Baader filter starts leaking at just below 1100 nm, which is in the region where the sensor sensitivity ends. So I guess there is a chance of some leakage pollution there.

[Stefano]

PS: looks like the Baader filter starts leaking at just below 1100 nm, which is in the region where the sensor sensitivity ends. So I guess there is a chance of some leakage pollution there.

In case you have a leak, KG glass could help.

[dabateman]

Steve, This highlights the challenge of describing a method for fluorescence.

 

Yes I get that in your example you need a U-340 on the flash, I'm not saying that you don't need a U filter.

 

What I was saying is that for UVIVF using a flash you'd only need to block the IR from the flash, if you had a camera which had been modified to image the UV-Vis-IR region. If you have an unmodified camera, I don't understand why there is a need to block the IR from the flash. Unless that is the internal filter stack of the camera is not sufficient to block the IR from the flash. Is that the case?

 

Hopefully that make sense now.

 

Jonathan,

You might be mixed up by our terms. UVIVF is ultraviolet induced visible fluorescence. For that you need pure ultraviolet (less than 400nm) to illuminate your subject. The camera should have cuts to collect only light between 400nm and 700nm.

 

UVIIRF is ultraviolet induced infrared fluorescence. For this you need pure ultraviolet light (less than 400nm) to illuminate your subject. The camera should have a blocking filter to only allow greater than 700nm.

 

If you use only S8612 on a flash and Lp720 filter om the camera, you will mostly be looking at visible induced IR fluorescence. As flash guns output the most at 550nm by design.

[dabateman]

Just to add, slightly unrelated. Some of my favorite images are created using ultraviolet light and just a S8612 filter on camera. I call thes UVvis, you get the UV reflective and hint of visible fluorescence.

 

Also my Em5mk2 is leaky enough to catch IR fluorescence. But you need long exposure time.

Steve you might have used UVIVF, when you meant UVIIRF.

[JMC]

Jonathan,

You might be mixed up by our terms. UVIVF is ultraviolet induced visible fluorescence. For that you need pure ultraviolet (less than 400nm) to illuminate your subject. The camera should have cuts to collect only light between 400nm and 700nm.

 

UVIIRF is ultraviolet induced infrared fluorescence. For this you need pure ultraviolet light (less than 400nm) to illuminate your subject. The camera should have a blocking filter to only allow greater than 700nm.

 

If you use only S8612 on a flash and Lp720 filter om the camera, you will mostly be looking at visible induced IR fluorescence. As flash guns output the most at 550nm by design.

 

No, I'm fairly sure I'm not getting mixed up with the terms.

 

What I'm saying is for UVIVF with a flash, why is it necessary to use a S8612 (or equivalent) on the flash, if the camera itself is unmodified and blocks any IR with its own filters? The IR from the flash would not be captured by the camera, assuming that is that the internal filtration of the camera is up to the job of blocking IR. Or are we saying that the IR from the flash needs to be blocked AND IR needs to be blocked from going through the lens for some reason.

 

I'm struggling to find another way of wording this, so don't worry about it.

[dabateman]

Ok I see now Jonathan. If using a Canon or Sony or Nikon camera with good IR stock IR blocking. Then you should be ok.

However, Olympus and Fuji cameras are IR leaky and enough to be seen in photos. I haven't tested my Panasonic well enough. But I think its also tight like a Nikon.

[Stefano]

Jonathan, as I said in post #29, you are correct in theory but reality can be different. 340 nm type glass, such as ZWB1, leaks before 700 nm, leaks also deep red. 360 nm type glass leaks at about 700 nm. So you may get deep red into the mix.

[dabateman]

See this as example of some cameras IR leakness:

https://kolarivision.com/uv-filter-effectiveness-article/

 

So Fuji is 5% at 704nm, if your U340 filter lets in 20% and the flash bright, than yes this may over power the weak visible fluorescence I have seen in some subjects.

My stock unmodified Olympus Em5mk2 lets in at least 10% in 700nm and I can see into 800nm.

 

Hope that is more clear.

[JMC]

David - Ok, good I'm not going mad then. So the internal filtration may not always be up to the job. In which case, yes the the IR needs filtering from the light source too.

 

Stefano - yeah I was referring to U-340 in my example, with ZWB glass all bets are off, and the more additional filtration the better.

[ulf]

9. “A Baader UV/IR cut filter over the lens plus a 2E or similar would be a safe way towards the end outlined by Steve.”

 

Following a thread elsewhere, I have obtained a 2A filter. But haven’t found a 2E at a price I’m willing to afford.

 

 

I do not really understand why Steve and Jonathan insist on a 2E-filter on the camera when using the Nemo as a light source.

In my opinion a 2A filter would be a good enough, or even a better alternative.

 

This is how I am reasoning:

If almost no light from the torch can reach the camera sensor everything should be OK.

Only if the fluorescence is exceptionally weak, a very powerful attenuation is needed.

 

I measured the direct output of the Nemo's LED without the filter and the VIS- cutting filters characteristics here:

https://www.ultravio...dpost__p__37933

 

The intensity from the LED at 400nm is rather low and combined with the filter that likely is a ZWB2, also measured in the same post, looking like a UG1, with an attenuation to less than 2% the remaining light intensity above 400nm from the torch must be very very low already.

 

The 2A filter has an attenuation to less than 0.5% of the incoming light at 400nm and below.

My spectrometric measurements show that here:

https://www.ultravio...dpost__p__39924

 

The only reason for using a filter like the 2E is if there is a need to eliminate some of the violet-blue spectra.

The 2E is a bit yellowish like some older lenses.

The 2A also show a weak yellow tone, but much less than the 2A.

 

If I am wrong, please show the flaws in my reasoning.

[dabateman]

Ulf,

It depends on your 2A and its age. When I first bought my Kodak wratten 2 2A 3x3 gel it let through 0% at less than 400nm. The cut off was about 405nm. But now it lets in at 395nm.

My 1952 21mm 2A filter I bought lets in UV better than some UV filters I have.

My Tiffen 52mm glass sandwich 2A still seems good. Should rescan it.

[ulf]

OK, that makes sense.

 

Organic gel filter sheets directly exposed to the environment might degrade over time.

They also will likely also degrade if exposed to powerful UV.

I expect that to be true for both 2A and 2E.

Then neither would be OK without spectrometric verification.

 

The Tiffen variants are likely more protected by their glass lamination.

 

My 2A is a laminated Tiffen filter.

[JMC]

Ulf, not sure I've ever mentioned about a 2E, have I? I like Zeiss T* for blocking (or my KV418, or even a 420nm longpass I got from Klaus) as they all have good blocking with about 50% max transmission in that 415-420nm region, and low fluorescence. I've not tried 2E.

[Cadmium]

Jonathan, OK, then you were saying that a visual range IR cutoff filter on the lens is redundant if you are doing UVIVF with a stock camera? Or with a full spectrum camera?

I am still confused by what you are saying.

 

Using a stock camera, such as may be demonstrated in the lower two photos compared here:

https://www.ultravio..._9952#entry9952

That may stand to reason, but I always filter my full spectrum camera with the same filter I use for visual range photos + the added UV barrier filter(s), when I am doing UV induced visual fluorescence.

I tend to use my stock D610 these days, in which case I don't use a visual range filter, but I still use the UV barrier filter.

 

We shouldn't scare people about the Wratten 2E, they work great for blocking UV. Very easy to test if you are anxious about them, just like with any other barrier filter using your 365 UV filtered light and your camera.

I have an old one and new one they both block the UV.

Although not exactly cheap unless you find a low priced used one, the Wratten 2E gel filters are one of the least expensive filters for this task, especially if you compare the price to some of the alternatives,

and I can't think of any others that are not more expensive. They come in different sizes, so make sure you get the size that will cover your lens.

They need a gel filter holder, which you can also find used, but all in all they are still the most inexpensive, and do a great job of blocking UV.

I fully endorse the Wratten 2E filter for this task.

 

Of course, I have not subjected either of them to my new Science Lab Destruction Chamber yet.

[Cadmium]

Bernard,

1) I think the Nemo 'should' work fir with the filter it has, but that is a U-360/UG1 type, according to Ulf, I think he thinks it is a ZWB2.

If you use the Baader U instead that would test for any problems, so I think you are good there.

 

2) as long as your IR bandpass filters are not leaking anything below their band, then I think you are good there also.

 

3) a 2E is about $55 new, that is the 3" size, price is +/- depending on size. You will only need that for UVIVF I think. Saw some used on eBay for about $30?

For UVIIRF using your three bandpass filters you won't need the 2E for that. Right?

 

4) The Baader UV/IR-Cut + Wratten 2E is a good stack, you could do that using GG240/GG235 also, if you stack the GG's between the Baader and the lens, but the 2E is still less expensive.

 

5) So what kind of exposure time are you needing to use for your UVIIRF shots?

[bvf]

Thanks, Cadmium.

 

You're right about 2Es being available for about $30. Trouble is, they're gelatin and I'm reluctant to use that. (As a kid with little cash I remember trying to cement a Wratten IR-pass gelatin filter between glass using Canada Balsam - that didn't go well!)

But I'll keep my eye open for a glass version.

 

I've ordered a Baader UV/IR cut filter - it will be useful for other applications as well.

 

UVIIRF exposure time varies depending on how big the subject is, of course. But using the Nemo torch, f/8, ISO 100 it is typically around a minute for the 750 nm filter, 4 times as much for the 850 nm filter, and 100 times as much for the 1000 nm filter. (Equivalent ratios for sunlight are 1:2:16, which indicates how much weaker the fluorescence is at longer wavelengths.) By comparison, around 10 seconds for UVIVF.

 

I've also started dabbling with VIIRF using a Lumitact G700 torch with S8612 + UV/IR cut. (Nice, bright torch - flat illumination with a zoom ability so you can concentrate the beam on the subject, and a cycle mount that you can use to fix it on a tripod.) Similar exposure times to UVIIRF.

[colinbm]

"Lumitact G700 torch" I am looking for a torch like this too, I want 6000k colour temperature, do you know the colour temp of this one please ?

[bvf]

Colin - unfortunately I don't know which colour temperature it offers. This is what I bought, but I can't see that info. in the description:

 

https://www.amazon.co.uk/gp/product/B07XKZRK83/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

 

It claims to use the Cree "Improved XM-L L2 LED chip (no other cheap small XM-L T6 LED chip)". I'm assuming this means the XM-L2. You can get the data sheet from here:

 

https://www.cree.com/led-components/products/xlamp-leds-discrete/xlamp-xm-l2

 

There are a number of different versions of that LED for different colour temperature ranges, but I don't know which one is in the Lumitact. I guess you could ask a local reseller or the AsiaPac distributor (my "manual" only gives the EU distributor).

[Ninjin]

I very like the colorful IR lum. I see no problem with colors. I think it's beautiful and has the art potential to work with it..

Several colors of IR lum I can get: This red, orange, yellow, turquoise-blue and blue, all "fake colors".

Of course, I slightly raised the brightness + _, but these are exactly the colors that I received on each wave of radiation. Colors are not changed. So it's quite accurate.

 

Infrared lum of cabbage:

I used a 720 filter which is unique (thanks Сadmium ❤).

It has different characteristics than 715 filter and Russian K19, and does wonderful things.

 

 

The cabbage head looks blue on the left and yellow on the right. But this is a controllable difference due to the difference in radiation. If you use the same emitter all the time, anyone will get the same color.

[Stefano]

Hi Ninjin, do you get red as a false IR color? Usually the palette of IR colors, when a "proper" white balance is applied doesn't contain any red. Maybe you processed your images in a different way?

[Ninjin]

false IR color

 

Hi Stefano!

Yes, red .. why would not red?

I always put the balance the same on cotton paper.. See the little gray-white 'flag' on the right this test photo? This is for my mark for balance. This "flag" is on all my photos, so it makes me for 'the same wb balance'. Usually it is on the edge and I cut it off after.

 

 

So false 'Red' is in front of 'Orange'. Cannot be seen with 720 filter but can be seen with K19 and earlier.

Even an IR photo can be taken separately..