Cyan-induced Infrared Fluorescence Experiment

[Andrea B.]

I tried out the cyan-induced infrared fluorescence experiment. I did get something. But like others who have been trying this, I wonder if I really captured IR fluorescence? I'm not sure I have a way to know.

 

Two different forms of cyan illumination were tried.

 

(1) 495 nm Photon Micro Light II, an LED

This is a tiny keychain Led which is surprisingly bright. The approximate, fully saturated RGB value for 495 nm is (0, 255, 203). This is seems close enough to the (0, 255, 255), 490 nm true cyan wavelength.

Linkie: http://www.batteryju...ton-ii-opt.html

 

(2) Visible Torch with S8612 (2.00mm) Filtration

The peak S8612 wavelength is approximately the desired 490 nm cyan.

 

For Infrared filtration on the lens I used the B+W 093.

 

Now, my doubts are as follows:

(1) Does the 495 Photon Micro LED output any IR? I wouldn't think so, but I don't know for a fact.

(2) Does the filtered torch output any IR? Probably, so the photo made with the torch would depend on whether the 2.00mm thickness of my S8612 is strong enough to block any of the torch IR. I cannot be sure.

(3) Does the B+W 093 pass any Visible light? I don't know for sure.

 

Camera: D600-broadband

Lens: Coastal Optics 60/4.0

Subject: Eupatorium rugosum aka White Snakeroot

 

Visible Reference

On-board fill flash used.

 

Ultraviolet Reference

A long exposure was taken to permit multiple flashes.

 

UV-Induced Visible Fluorescence

There's not much really. I used the camera's preset Visible white balance which was preserved during conversion. This is pretty close to what I saw although maybe a bit more saturation.

Illumination via Nichia 365nm UV LED. Baader UVIR-cut filter on lens.

 

Cyan LED Illumination with Infrared Lens Filtration

Lens set wide open at f/4 so that exposure time could be shortened.

 

Cyan Filtered Torch Illumination with Infrared Lens Filtration

Lens set wide open at f/4 so that exposure time could be shortened.

 

Raw Composites and Histograms

To support the case for claiming that I've captured Infrared fluorescence, I offer up the raw composites and histograms for the cyan illuminated photos to show that they look like every typical B+W 093 photo I've ever taken in the past. And the histograms do not appear to show cyan illumination.

 

 

 

 

 

 

Comments and questions are always welcomed!!

 

Thanks to all those members who have been experimenting with cyan. You work has encouraged me to try something new. :)

[Cadmium]

Don't know.

Dark room, right?

Try a different flower.

Try a comparison between IR LUM and IR. Shoot one with the visual light/filtered, then another with no filter. See if they look any different.

Got any cadmium around for a test?

 

Also:

Try a test in live view, look at your filtered light with the 830nm filter, see if it sees light, how much... it should not see any or at least extremely dim.

[Guest]

Hi Andrea,

 

I agree, it does look like your cyan illuminated images are IR images (vs. IR fluorescence images). I had this very same problem. I think its a good idea to take IR illuminated reference images for comparison.

 

I tried filtering IR out of my cyan LED source (even though I don't think it outputs much of any, if any, IR in the first place). I did this using a triple stack of IR blocking/absorbing filters - and it did not make a difference (thus, I think that confirms IR contamination from the LED source is not an issue). Ambient IR is an issue of course - and as I'm sure you know, at 10-15s exposure it doesn't take much at all.

 

My next step in capturing CyIIRF is to figure out some way to calibrate the images. My idea is to include in the images some small target with known IR fluoresce. This would help to set exposure and get an idea of the relative intensity of the subject's fluorescence.

 

Now, if I can just find something which only fluoresces in IR... (any suggestions?)

[Andrea B.]

I agree that IR output from the LED does not appear to be a general problem for visible color LEDs. We should always verify that as best we can when using a new LED.

 

The problem with comparing Infrared fluorescence photos to Infrared reflection photos is that they can look alike. We have the same problem with visible fluorescence versus visible reflection. In either case we can only know that we have fluorescence because of our experimental setup: in the dark so there is no ambient contamination and use of strong excitation filtration and strong barrier filtration.

 

I went searching through various optical material manufacturer's websites for some kind of fluorescent standard. But so far only found visible fluorescence standards. In the medical literature it seems that various dyes and solutions or such things as microscopic fluorescent "beads" are used as standards for infrared fluorescence. I also found that there are entire books written about medical fluorescence imaging. They are not using DSLRs or mirrorless cameras, of course. This is all done with medical equipment. It's not clear to me that we could make use of any of their test standards even if we could somehow procure them.

 

I think swatches of certain pigments might work for IR-only fluorescence. Somewhere I have a link to pigment test pages. I'll return with that in a while.

 

I also recall from somewhere that plants which are monocots are prone to IR fluorescence. Monocots include plants like orchids, certain grasses like wheat or bluegrass, flowers grown from bulbs like tulips or lilies.

 

Identification of pigments by multispectral imaging; a flowchart method

by Albert Cosention

in Heritage Science, March 2014

https://heritagescie...6/2050-7445-2-8

In this work the Heliopan RG1000 filter was used for Infrared. That is seriously way up there!

Cadmium based pigments exhibit Infrared fluorescence.

 

 

Phycoerythrin-Cyanin7 = PE-Cy7 = PE/Cy7 is a dye combination whose peak excitation wavelength is 488 nm (cyan=490nm) and peak emission wavelength is 755 nm in the Infrared. http://www.bdbioscie...guide/index.jsp

[colinbm]

Hi Andrea, are there any of the dyes pigments in the Color Checker that fluoresce in UVIVF &/or VIIRF, please ?

Cheers

Col

[rfcurry]

Since you are getting Stoked, is anyone going for Anti-Stoked? I notice in another thread that Andy P. is using anti-Stoke pigments (photon upconversion phosphors) for recording 1550nm NIR. Are there natural pigments that fluoresce due to photon upconversion?

[Andrea B.]

Good question, Col.

I stepped into the dark closet for a quick check with the Nichia 365 UV-Led. There does seem to be some response on the CC Passport color patches. I'll get a photo of that later to post for everyone.

 

Reed, isn't anti-stoking rather rare??

[Cadmium]

Cadmium glows like a light bulb in VIIRF. It is the strongest IR fluorescing material I have tried.

I was only using a MAG-LITE flashlight with an incandescent/filament type bulb for this test below. The flashlight was filtered with a Schott VG9 + Schott S8612 stack.

The weak point of that setup was the flashlight power. Better to use a small filtered flood.

The cadmium fluoresces very strongly in IR, so be prepared for longer exposures to see IR fluorescence from most other materials.

 

[colinbm]

Thanks Andrea, all my UV photography gear is packed away, but will be coming out again soon.......

Col