IR Fluorescence

Some examples of IR, UVIVF, and IR fluorescence. I used a Sony RX100 MK 2. All image, at wide angle 28mm. IR and UVIVF photos were added, for comparison. UVIVF (Visible fluorescence from UV, in B&W) with Full Spectrum camera and external Hot Mirror. ~10 seconds. Single Nichia 365nm UV Flashlight, ISO 160, F/8

IR at ~850nm using single IR led with Full Spectrum camera F/8, ~1 second

with Full Spectrum camera, 365nm Nichia Flashlight, and 30" at F/2 ISO 160 using 850nm filter

Nice but I prefer to see UVIF in colour, the induced florescence does tend  to be quite colourful (and is actually easier to capture without a modified camera). The UV image is in my experience much more difficult to achieve, even with a modified body.

My own experiments with UVIF have so far nearly all been with artificial subjects which fluoresces very easily (allowing less care in blocking out ambient light). It's high time I tried doing it properly 

The UV induced IR Fluorescence image made me wonder if the parts fluorescing are the same as the parts absorbing UV. i.e. Darker parts in a reflected UV image are not where UV is simply absorbed, but rather where the energy from the UV light is partly absorbed, then reflected back as IR.

However, doing a quick very non-scientific test with a daisy I couldn't see this. Not sure if this is just my poor test setup (it wasn't light tight so I would get an IR image even without any UV light sources). Or it's that UV absorption in flowers does not guarantee UV induced IR fluorescence, and it varies between species.

After trying my test though, I think you must have a very good light tight setup considering the excellent images you produced and the exposure times.

DavidKennard wrote:

The UV induced IR Fluorescence image made me wonder if the parts fluorescing are the same as the parts absorbing UV. i.e. Darker parts in a reflected UV image are not where UV is simply absorbed, but rather where the energy from the UV light is partly absorbed, then reflected back as IR.

However, doing a quick very non-scientific test with a daisy I couldn't see this. Not sure if this is just my poor test setup (it wasn't light tight so I would get an IR image even without any UV light sources). Or it's that UV absorption in flowers does not guarantee UV induced IR fluorescence, and it varies between species.

After trying my test though, I think you must have a very good light tight setup considering the excellent images you produced and the exposure times.

oh wow! and after reading that, I realized that I had at one time thought along the same line. If that's the case indeed, then I could at least in theory create a UV-reflectance image (at least of small subjects and areas) using meticulous advanced processing. I might need to think about it quite comprehensively to know whether such processing would exactly recreate a UV-image, but not totally out of the question. As for the setup being light tight- yes, I've typically tried to get things perfect in photography, especially after reading some forum posts over at Ultravioletphotography.com about UV-induced IR. It's quite an interesting website. if you ever get a chance, you might want to check it. I've had trouble becoming a member, mainly because I've not figured how to access the sign-in process. at the time of the photo, I actually was using a filter adapter onto which I attached two stepping rings, to be able to attach the 58mm IR onto the 49mm filter adapter for the Sony RX100 MK2.

If you don't have a UV pass filter to give you reflected UV images, you might be able to find suitable reference images online that others have taken. On the hand, given how long your UV induced IR fluorescence exposure was and how light tight your setup appears to be, I suspect you could get a UV image just using a UV light source with no filtration on the camera necessary.

In my quick test for the reflected UV image I was getting 2s @ ISO 200 f/5.6 with a EL-Nikkor 63mm/2.8 N lens and Baader U filter, lit with a Convoy S2+ Nichia 365nm flashlight (placed pretty close to the flowers). So assuming the light doesn't output in the IR (not 100% sure if this is the case) it should give you an image where the vast majority of light recorded is UV.

I agree on the ultravioletphotography.com recommendation. I don't think I am a member there, but there is a wealth of excellent information freely available to read there.

DavidKennard wrote:

If you don't have a UV pass filter to give you reflected UV images, you might be able to find suitable reference images online that others have taken. On the hand, given how long your UV induced IR fluorescence exposure was and how light tight your setup appears to be, I suspect you could get a UV image just using a UV light source with no filtration on the camera necessary.

In my quick test for the reflected UV image I was getting 2s @ ISO 200 f/5.6 with a EL-Nikkor 63mm/2.8 N lens and Baader U filter, lit with a Convoy S2+ Nichia 365nm flashlight (placed pretty close to the flowers). So assuming the light doesn't output in the IR (not 100% sure if this is the case) it should give you an image where the vast majority of light recorded is UV.

I agree on the ultravioletphotography.com recommendation. I don't think I am a member there, but there is a wealth of excellent information freely available to read there.

Interestingly, the Sony RX100 II lens might be able to block an enormous amount of UV. I had hopes for possibly obtaining a UV filter for it in the past, but I shined the UV flashlight for a moment at the lens, which seemed very hazy and fogged up, as UV-blocking glasses also did. I assumed that the lens might contain strong UV-coating on it. The lens has the Zeiss T* logo on it, which from my immediate memory might've indicated the coating but I might be able to google it here in a moment.

I've seen an example online somewhere of a color sensor being able to see UV-A as blue, while UV-B could be seen as green. That could be really interesting, especially combining in various ways with visible channels and IR. In addition, I've also been looking for something like Schott RG1000.

MacM545 wrote:

DavidKennard wrote:

If you don't have a UV pass filter to give you reflected UV images, you might be able to find suitable reference images online that others have taken. On the hand, given how long your UV induced IR fluorescence exposure was and how light tight your setup appears to be, I suspect you could get a UV image just using a UV light source with no filtration on the camera necessary.

In my quick test for the reflected UV image I was getting 2s @ ISO 200 f/5.6 with a EL-Nikkor 63mm/2.8 N lens and Baader U filter, lit with a Convoy S2+ Nichia 365nm flashlight (placed pretty close to the flowers). So assuming the light doesn't output in the IR (not 100% sure if this is the case) it should give you an image where the vast majority of light recorded is UV.

I agree on the ultravioletphotography.com recommendation. I don't think I am a member there, but there is a wealth of excellent information freely available to read there.

Interestingly, the Sony RX100 II lens might be able to block an enormous amount of UV. I had hopes for possibly obtaining a UV filter for it in the past, but I shined the UV flashlight for a moment at the lens, which seemed very hazy and fogged up, as UV-blocking glasses also did. I assumed that the lens might contain strong UV-coating on it. The lens has the Zeiss T* logo on it, which from my immediate memory might've indicated the coating but I might be able to google it here in a moment.

I've seen an example online somewhere of a color sensor being able to see UV-A as blue, while UV-B could be seen as green. That could be really interesting, especially combining in various ways with visible channels and IR. In addition, I've also been looking for something like Schott RG1000.

That's quite common. Modern anti reflective coatings are designed to maximise visual transmission & this can cause non visual wavelengths to be significantly reduced, add to that the typically poor UV transmission of normal glasses & the amount of glass in complex lenses...

The el-nikkor lens used by David is one that is well known for good UV transmission - not up to the standards of special Quartz hyper-chromatic lenses but at least $1000 cheaper.

petrochemist wrote:

MacM545 wrote:

DavidKennard wrote:

If you don't have a UV pass filter to give you reflected UV images, you might be able to find suitable reference images online that others have taken. On the hand, given how long your UV induced IR fluorescence exposure was and how light tight your setup appears to be, I suspect you could get a UV image just using a UV light source with no filtration on the camera necessary.

In my quick test for the reflected UV image I was getting 2s @ ISO 200 f/5.6 with a EL-Nikkor 63mm/2.8 N lens and Baader U filter, lit with a Convoy S2+ Nichia 365nm flashlight (placed pretty close to the flowers). So assuming the light doesn't output in the IR (not 100% sure if this is the case) it should give you an image where the vast majority of light recorded is UV.

I agree on the ultravioletphotography.com recommendation. I don't think I am a member there, but there is a wealth of excellent information freely available to read there.

Interestingly, the Sony RX100 II lens might be able to block an enormous amount of UV. I had hopes for possibly obtaining a UV filter for it in the past, but I shined the UV flashlight for a moment at the lens, which seemed very hazy and fogged up, as UV-blocking glasses also did. I assumed that the lens might contain strong UV-coating on it. The lens has the Zeiss T* logo on it, which from my immediate memory might've indicated the coating but I might be able to google it here in a moment.

I've seen an example online somewhere of a color sensor being able to see UV-A as blue, while UV-B could be seen as green. That could be really interesting, especially combining in various ways with visible channels and IR. In addition, I've also been looking for something like Schott RG1000.

That's quite common. Modern anti reflective coatings are designed to maximise visual transmission & this can cause non visual wavelengths to be significantly reduced, add to that the typically poor UV transmission of normal glasses & the amount of glass in complex lenses...

The el-nikkor lens used by David is one that is well known for good UV transmission - not up to the standards of special Quartz hyper-chromatic lenses but at least $1000 cheaper.

Makes sense. I've been really thinking about using a specialty lens along with a full spectrum Micro 4/3rds, or a Canon SLR (is mirrorless possible?). I read from ebay, of lenses specially made for UV that are under $150. Panasonic GX85 or G7 might be an interesting choice for such a lens. As for the el-nikkor lens, I've read about UV-capable lens comparisons before. Thanks that might also be a lens I might consider.

Regarding lenses suitable for UV photography, I had good luck buying one with good filters from e Bay seller "igoriginal". The set I bought was like this: https://www.ebay.ca/itm/273863933139?hash=item3fc38ffcd3:g:CEMAAOSwvv9ZgSTM

Best wishes,
Sterling
--
Lens Grit

SterlingBjorndahl wrote:

Regarding lenses suitable for UV photography, I had good luck buying one with good filters from e Bay seller "igoriginal". The set I bought was like this: https://www.ebay.ca/itm/273863933139?hash=item3fc38ffcd3:g:CEMAAOSwvv9ZgSTM

Best wishes,
Sterling
--
Lens Grit

oh yeah, he's even posted more lenses, for various camera brands. That's the seller I was going to get one from.

petrochemist wrote:

MacM545 wrote:

DavidKennard wrote:

If you don't have a UV pass filter to give you reflected UV images, you might be able to find suitable reference images online that others have taken. On the hand, given how long your UV induced IR fluorescence exposure was and how light tight your setup appears to be, I suspect you could get a UV image just using a UV light source with no filtration on the camera necessary.

In my quick test for the reflected UV image I was getting 2s @ ISO 200 f/5.6 with a EL-Nikkor 63mm/2.8 N lens and Baader U filter, lit with a Convoy S2+ Nichia 365nm flashlight (placed pretty close to the flowers). So assuming the light doesn't output in the IR (not 100% sure if this is the case) it should give you an image where the vast majority of light recorded is UV.

I agree on the ultravioletphotography.com recommendation. I don't think I am a member there, but there is a wealth of excellent information freely available to read there.

Interestingly, the Sony RX100 II lens might be able to block an enormous amount of UV. I had hopes for possibly obtaining a UV filter for it in the past, but I shined the UV flashlight for a moment at the lens, which seemed very hazy and fogged up, as UV-blocking glasses also did. I assumed that the lens might contain strong UV-coating on it. The lens has the Zeiss T* logo on it, which from my immediate memory might've indicated the coating but I might be able to google it here in a moment.

I've seen an example online somewhere of a color sensor being able to see UV-A as blue, while UV-B could be seen as green. That could be really interesting, especially combining in various ways with visible channels and IR. In addition, I've also been looking for something like Schott RG1000.

That's quite common. Modern anti reflective coatings are designed to maximise visual transmission & this can cause non visual wavelengths to be significantly reduced, add to that the typically poor UV transmission of normal glasses & the amount of glass in complex lenses...

The el-nikkor lens used by David is one that is well known for good UV transmission - not up to the standards of special Quartz hyper-chromatic lenses but at least $1000 cheaper.

Thanks petrochemist. but only $1000?! I thought that Quartz lenses are at least $6,000. I've looked up a "Like New" condition lens- exactly the one nikkor you've mentioned that David has used. It seemed extremely cheap. I don't remember as of now exactly how much it cost, but less than $400, maybe even below $300.

Hi David. I don't know if you've got time, but I've found something really interesting about the UV transmission of the Sony lens. I used the Nichia 365nm torch, which I shined through a polarized glass lens from a set of sunglasses. Before I go on though. I was going to mention, polarized glasses look pretty much transparent out in sunlight with a full spectrum camera with 850nm IR filter- in fact, from my memory, they might've been clear as a window. The Sony was pointed at the 365nm torch, which was shining through the polarized glass. Interestingly, there seemed to be some darkening going on versus the torch being pointed at the camera from the same angle and distance, without any filtration but with the 850nm filter. It was akin to using maybe a 3-stop to 4-stop, maybe 5-stop, ND in front of a regular (unmodified camera)!

Come to think about it during writing this post though, it might've been an IR LED instead. I might need to redo this test to see what exact light source was involved, but I might also do a test with a prism in sunshine, using the prism in order for the creation of a rainbow; this way, it might be easier and more definitive than the aforementioned polarized/IR idea. of course, the prism must be able to transmit UV light in addition to the visible light, but the entire thought about this stuff has made me want to get a spectrometer.

MacM545 wrote:

Thanks petrochemist. but only $1000?! I thought that Quartz lenses are at least $6,000. I've looked up a "Like New" condition lens- exactly the one nikkor you've mentioned that David has used. It seemed extremely cheap. I don't remember as of now exactly how much it cost, but less than $400, maybe even below $300.

Probably at least $6000, yes. I hadn't seen one for sale for a while & couldn't be bothered to look. I should have said 'much more than' rather than 'at least'

MacM545 wrote:

Hi David. I don't know if you've got time, but I've found something really interesting about the UV transmission of the Sony lens. I used the Nichia 365nm torch, which I shined through a polarized glass lens from a set of sunglasses. Before I go on though. I was going to mention, polarized glasses look pretty much transparent out in sunlight with a full spectrum camera with 850nm IR filter- in fact, from my memory, they might've been clear as a window. The Sony was pointed at the 365nm torch, which was shining through the polarized glass. Interestingly, there seemed to be some darkening going on versus the torch being pointed at the camera from the same angle and distance, without any filtration but with the 850nm filter. It was akin to using maybe a 3-stop to 4-stop, maybe 5-stop, ND in front of a regular (unmodified camera)!

Come to think about it during writing this post though, it might've been an IR LED instead. I might need to redo this test to see what exact light source was involved, but I might also do a test with a prism in sunshine, using the prism in order for the creation of a rainbow; this way, it might be easier and more definitive than the aforementioned polarized/IR idea. of course, the prism must be able to transmit UV light in addition to the visible light, but the entire thought about this stuff has made me want to get a spectrometer.

In terms of sunglasses looking transparent when photographed in IR, I would think this is not to do with the polarisation, but rather with the dyes / material the sunglasses are made from. Likely they are only made to reflect / reduce visible light, not IR. Cheaper plastic ND filters have the same effect - they will reduce the visible light, but not the IR.

In terms of pointing a UV light through sunglasses, I would think that most glasses would have UV blocking coatings that block most of the UV.

Do you mean with your experiment you shone a UV light through polarised sunglasses, and the resultant image looked like it was taken with visible light and a strong ND filter? I can't really offer any explanation for that. (I guess technically it is possible the UV light could be converted to visible, but I would think a light leak from a visible source would be more likely).

DavidKennard wrote:

MacM545 wrote:

Hi David. I don't know if you've got time, but I've found something really interesting about the UV transmission of the Sony lens. I used the Nichia 365nm torch, which I shined through a polarized glass lens from a set of sunglasses. Before I go on though. I was going to mention, polarized glasses look pretty much transparent out in sunlight with a full spectrum camera with 850nm IR filter- in fact, from my memory, they might've been clear as a window. The Sony was pointed at the 365nm torch, which was shining through the polarized glass. Interestingly, there seemed to be some darkening going on versus the torch being pointed at the camera from the same angle and distance, without any filtration but with the 850nm filter. It was akin to using maybe a 3-stop to 4-stop, maybe 5-stop, ND in front of a regular (unmodified camera)!

Come to think about it during writing this post though, it might've been an IR LED instead. I might need to redo this test to see what exact light source was involved, but I might also do a test with a prism in sunshine, using the prism in order for the creation of a rainbow; this way, it might be easier and more definitive than the aforementioned polarized/IR idea. of course, the prism must be able to transmit UV light in addition to the visible light, but the entire thought about this stuff has made me want to get a spectrometer.

In terms of sunglasses looking transparent when photographed in IR, I would think this is not to do with the polarisation, but rather with the dyes / material the sunglasses are made from. Likely they are only made to reflect / reduce visible light, not IR. Cheaper plastic ND filters have the same effect - they will reduce the visible light, but not the IR.

In terms of pointing a UV light through sunglasses, I would think that most glasses would have UV blocking coatings that block most of the UV.

Do you mean with your experiment you shone a UV light through polarised sunglasses, and the resultant image looked like it was taken with visible light and a strong ND filter? I can't really offer any explanation for that. (I guess technically it is possible the UV light could be converted to visible, but I would think a light leak from a visible source would be more likely).

Most polarisers transmit NIR but there are some expensive models made that polariser IR too.

I've used a spectrometer to test transmission of a variable ND filter (which is 2 polarisers in series) With the polarisers crossed to block all visual light, I saw transmission starting about 740nm (1% transmitted) by about 775nm this had reached 10% and from 900nm to 1100nm values of 70 to 80% where seen.

With the polarisers aligned (it's palest setting) transmission started at 390nm (1%)

Mine reached 10% at 399nm & 30% by 425nm and continued to rise gradually throughout the visible range (keeping between 40 & 50% from 480nm to 730nm) Most of the IR transmission was very close to that seen at the darker setting.

Some of the fancy coloured polarisers I have show trace transmission in UV, one of them getting close to 0.5% at 350nm.

If a UV light is producing a recordable light level when shone through a polariser it seems likely that the polariser dye is exhibiting some Ultra violet induced fluorescence, quite common where intense UV lights are used. However transmission testing with a camera is generally not very accurate. Stray light is a major cause of errors in such testing and is seen even in advanced laboratory spectrometers our dual monochromator research instrument gets unreliable below 0.1% despite being fully enclosed with multiple light baffles...