Increasing the UV (ultraviolet) light output of a Xenon flash

Today about a increasing the output of a Xenon flash system aside from what I have posted here before. I have to issue a warning: ALL THE FOLLOWING INFORMATION CONTAINS INFORMATION THAT COULD CAUSE DAMAGE TO YOUR HEALTH AND SHOULD ONLY BE DONE IF AND WHEN THE NEEDED EXPERIENCE IS THERE AS WELL AS THE NEEDED SAFETY MEASURES SUCH AS EYE AND SKIN PROTECTION! ALL RISK WILL BE ON YOU IF YOU REPEAT FOR YOURSELF WHAT I WILL DESCRIBE IN THE FOLLOWING! Well, after having said that, let me briefly describe what I have done.

What I have done is, that after I have taken out the Xenon tube from a flash system I etched away the UV blocking metallic coating by bathing it for about 20-30 minutes in 30% HCL acid (Hydrochloric acid) using proper eye and hand protection, under a running exhaust, with cleaned water to rinse the tube while and after the procedure and making sure not to bump the Xenon tube anywhere, as it is under very high pressure and it may explode if not properly handled. Only the glass tube should be in contact with the acid, not the metallic conductors leading into the tube. Further, this only works, if the tube has a metallic ingnitor wire around it and NOT if the metallic coating also works as ignitor - etching that away renders the tube useless and it would most likely not fire anymore.

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Transmission of a Xenon tube before/while/after/:


So what you see here is the transmission of my Xenon tube before (pink line), while (yellow line) and after the procedure (red line). The difference is quite significant, yielding a total 1.8 stop increase in transmission = output power at 365nm and even more importantly, a much deeper reach into the UV region beyond 300nm. I'm not predicting that this will work with any tube, but that yellowish tube I had, turned out to be perfectly clear afterwards. Another method is to erase that coating using Cerium Oxide abrasive powder, but personally I haven't done that.

AGAIN; DON'T DO THAT IF YOU ARE NOT WELL AWARE OF THE INHERENT DANGER!!

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

[UV, FL] Roman Artifacts paint / glaze visibility

A study conducted for a friend using some excavated roman artifacts. The idea was to see, if deteriorated paint/lead glacing could be made visible after thousands of years, using these new high powered Nichia 4 dice UV LEDs (365nm + 385nm).

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1) Visible light shot: 


2) FL (385nm Nichia UV LED induced visible fluorescence): 


3) FL (365nm Nichia UV LED induced visible fluorescence): 


4) differential 1 - 2 


5) differential 1 - 3 


Interestingly enough, the induced fluorescence was quite different, although the LED emissions are just 20nm apart. A comparison was done to see, if a nearly monochromatic excitation using UV LEDs would provide a different result than a wide band filtered Xenon lamp (300-400nm) excitation, which was not the case (not shown here). 

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Aster hybride meets Noflexar 35mm lens

Today few shots of an Aster hybride using the Noflexar 3.5/35mm lens and various filters.
No noticeable patterns, as expected though.

[click on image to see a larger one]

visible light shot: 


UV shot (using Baader U-filter and Xenon flash): 


Butterfly vision shot (using my XBV2 filter): 


UV induced visible flourescence shot (using Baader UV/IR Cut filter and Nichia 365nm UV light): 


As boring as it might look like, this now is quite interesting (to me) as it shows UV induced IR fluorescence. Lights were all Nichia UV LED sources I could get hold of (to make sure not a bit of IR would be present), a B+W 092 cut filter (>65nm) in front of the lens and 30sec exposure in total darkness:
 


With the naked (but UV protected!!) eye quite a bit deep red fluorescence gets visible, but hard to ban that on a photo....

Same experiment but using a dark orange filter and same UV lighting setup in darkness (Nichia 4x 365nm LED using a front attached Baader U-filter to block any visible light!):



I have now found a reliable method to professionally infinity convert Noflexar 35mm lenses to Nikon mount - ask me if you need one!

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Fluorescence: Rudbeckia missouriensis using various light sources + filters

A quick series of tests done, showing the effects of various UV light sources + filters for UV stimulated visible fluorescence. Images just resized, straight from the cam.

[click on image to see a larger one]

0. Visible reference, 5600 Kelvin LED



1: Long wave UV lamp w. filtered mercury 2x 4 Watts lights ("blacklights"), 400-700nm dichroic cut filter on camera



2: Cree 385nm UV LED, 3 Watts, 400-700nm dichroic cut filter on camera (this LED leaks quite some blue light)




3: Cree 385nm UV LED, 3 Watts, filtered using 1.25" BaaderU-Filter , 400-700nm dichroic cut filter on camera



4: Nichia 385nm UV LED, 400-700nm dichroic cut filter on camera

5: Nichia 365nm UV LED, 400-700nm dichroic cut filter on camera

6: Nichia 365nm UV LED filtered using 1.25" BaaderU-Filter, 400-700nm dichroic cut filter on camera



7: High Power UV flash, filtered using Schott UG1, 400-700nm dichroic cut filter on camera



8: High Power UV flash, filtered using Schott UG1, Baader UV/IR cut filter on camera



9: High Power UV flash, filtered using Schott UG1, Schott BG38 + 400-700nm dichroic cut filter on camera



10: High Power UV flash, filtered using Schott UG1, 400-650nm dichroic cut filter on camera

Exposure times were between 15s (UV fluorescent lamp), 3-15s (UV LEDs) and 1/160s (Xenon flash), all shot using ISO400 and f11.

I did not try and make "the pattern" visible. The underlying assumption that the pattern using reflected UV and UV stimulated visible fluorescence should not be confused, since it is two completely different mechanisms and it might be just coincidential that both appear at the same time. It would be interesting to study that though, if these both are directly linked to each other (i.e. if the reflected UV pattern and the fluorescence pattern appear simultaneously and if so, why).

You may have noticed, that I tried to cut off the visible part of the exciting light source from about 395nm onwards using a 1.25" Baader U-filter in some of the tests. I wanted to see if that "leakage" of visble light (some blue usually) in the exciting light has an impact on the result - and quite obviously it has, with the exception of the Nichia 365nm UV LED, since that one has hardly any visible content. But still it makes a little, but noticeable difference.

The Xenon light source provides a continuous emission spectrum and using a UG1 like filter, I took out the UV part as exciting light. Now the question is, if the strong visible red in the results is a result of stimulated red+NIR fluorescence, or if it is caused by NIR leakage of the UG1 filter (i.e. reflected NIR). This is why I used three different  filters (BG38, Baader UV/IR cut and 400-650nm cut) to see the effect of them.

Here now the proof that IT IS indeed red/NIR leakage:

11: High Power UV flash, filtered using Schott UG1, 400-700nm dichroic cut filter on camera



12: High Power UV flash, filtered using Schott UG1 + UV passing IR blocking filter, 400-700nm dichroic cut filter on camera

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Creeping Zinna, multispectral, UV induced fluorescence, reflected UV etc.

A walk over the local market not only brought some nice white "Lambertheimer" asperagus and new "Galatiner" potatoes home, nope, also a nice "Creeping Zinna" (Sanvitalia procumbens) plant made it to my balcony.

An ideal target to test out the UV enhanced High Power Xenon, the XUVIR "one shot" filter, the Xcut2 filter as well as the well known Baader U filter.

Equipment used was: Nikon D70 (unmodified), UV Nikkor 105mm lens @ ISO400, f11, 1/180sec.

[click on image to see a larger one]

VIS using XCUT2 filter (400-650nm):


UV using Baader U-filter (310-390nm):


XUVIR multispectral filter (300-1000nm), UV Flash:


XUVIR filter (300-1000nm), unfiltered flash for multispectral recording


UV induced fluorescence using XCUT2 filter (400-650nm), UV flash:


Sanvitalias UV pattern is actually not that easy to shoot. That may been seen if you have a look at the reflection spectra which I took, since the UV reflection of the petal tip (white line) is less than 10%, just a little bit more than the rest of the petal (teal line) which has hardly any UV reflection. At the same time the IR reflection is very high. So very careful filtering and a strong UV source is needed :


So, as you may see, a variety of results may be produced....and yes, the asparagus was delicious...

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Carnivore plant shows UV pattern

A friend of mine, Dr. Andreas Wistuba, collects and breeds special forms of carnivore plants and we were both wondering if some would show some UV reflective patterns. Well indeed, some do on these "needles" which prevent their prey to escape!!

Shot using off the shelf D70, UV-Nikkor 105mm, SB-140 flash + 2" Baader U-filter (310-390nm) (resp. UV blocking filter for the fluorescence shot)
[click on image to see a larger one]
UV shot:


UV shot detail:


Fluorescence shot:

Not sure what caused that, but evolution surely had a reason to develop that UV pattern!

Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Filters for UV induced visible Fluorescence

Here now an overview and comparative test of filters for UV induced visible fluorescence, as an outcome of a recent test I made using a Phalaenopsis as a target. I was using for that test my newly developed High Power UV Flash with UV transmitting front filter to stimulate UV induced visible fluorescence.  As optics I used the X35 lens at f8, 1/160 exposure time and the various mentioned filters (but any good lens for visible photography would obviously do).

Just a reminder: The intention was to find a filter, which allows to record visible fluorescence in the 400-650nm range. Deep red or NIR flourescence >650nm is tricky to record, since it coincides with NIR (near infrared) transmitted from the flash, so it would be wiped out in the resulting images (IR leakage). To record that, either a NIR blocking but UV transmissive flash front filter has to be used (a bit tricky, but could be done by sandwiching a BG38 or BG40 filter in front of the UV transmissive flash filter), OR a excinting source like the Nichia 365nm UV LED has to be used, which emits no NIR/IR at all.

[click on image to see a larger version]

1. Schott BG38 filter, transmits UV, but filters out IR - NOT useful


2. Commercial noname IR Cut filter, obviously transmits UV, blocks IR - NOT useful


3. Omega UV cut, IR blocking filter (from 650nm onwards) - too much blue also cut off (missing blue)


4. Baader UV IR Cut filter - nice colors, but transmits to about 700nm, which creates an
issue with most UV transmissive flash filters, since NIR is transmitted (too bright reds)


5. Baader UV IR Cut filter + IR cut filter (from 650nm onwards) - nice and UV flash issue
also nicely covered; but needs two stacked filters


6. Xcut filter, UV + NIR cut, transmits ca 410-650nm - works nicely, the best, all in just one filter


7. Xcut2 filter, UV + NIR cut, transmits ca 400-650nm - works nicely, bit on the cold side with enhanced blue, all in just one filter


8. Tiffen Hotmirror - quite some UV bleed through - NOT useful
[identical to the Canon Hot Mirror Filter btw.]


9. B+W 489 IR blocking filter - quite some UV bleed through - NOT useful
[the B+W 486 digital UV IR cut filter cuts on at 370nm, so it will be about the same, NOT useful result]


10. Noname Hot Mirror Filter - quite some UV bleed through - NOT useful


...and just for the fun of it and for comparison....purely reflected UV...
Baader U-filter ("Venus") 310...390nm


Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

High Power UV Flash for stimulated visible Fluorescence

Here a recent test I made to see if my newly developed High Power UV Flash would be able with just one pop to stimulate UV induced visible fluorescence. I used the X35 lens at f8, 1/160 exposure time and a Xcut blocking filter (prototype) ,which only allows 400-650nm vivible light to pass and thus also controls the risk of IR leakage coming from the flash, since Xenon emits plenty of IR. The flash itself is modified for high UV output and uses a quartz flashtube plus a UV transmissive, visible light blocking filter.

The following pic is (C) Michigan State University and shows clearly the high IR output of a normal Xenon flash (red line). The blue line however shows the effect of a flash circuit modification, allowing more amps per square centimeter to pass through the Xenon plasma, so as to enhance UV output and suppress the usually high IR content.

Here now the shot and the proof that the High Power UV Flash idea works to stimulate visible fluorescence:

[click on image to see a larger version]

And now how fluorescent minerals look like using that flash.

All fluorescent minerals from the famous Franklin Mine/USA:

Stay tuned, more will follow on that fascinating subject... More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Teeth and UV I

Today about teeth and ultraviolet photography.

I found in some older books some contributions of Prof. Woods and esp. Ch. Lunnon about photograping teeth using ultraviolet light.

So here some results using my calibrated for UV X35 lens, a Baader 2" U-filter and my newly developed High Power UV flash.

The top image clearly shows, repairs, cracks, plaque etc. whereas the second one using a special filtering technique also shows bacteria build up (plaque) as reddish cast and repairs having being done. The small size of the images here do not really show the amount of detail which gets visible using these techniques.

[click on image let's you see a larger image]





Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos

Primula II ... UV induced visible Fluorescence

So today a flower fell of that beautiful Primula plant. I had bought that for my balcony, since I needed some colors around me after a long a dark winter, which is finally over here in Weinheim / Germany

I grabbed my camera, attached a long extention tube, plus that tack sharp UV Rodagon 60mm lens. This following shot was done using a tungsten cold fiber light: [as usual, a click on an image opens up a larger view]



So if we switch from visible light to UV light, in this case using my 365nm Nichia UV LED flash/lamp, we will see the pollen light up blueish / greenish and also the colors of the flower petals change. I had to remember to use a UV stopping filter in front of the lens, in this case the 2" Baader UV/IR Cut filter, which also stops IR light very efficiently, needed for modern DSLRs due to their very high IR sensitivity. This is the result now, called UV induced visible fluorescence, commonly called fluorescence [there are other forms of fluorescence, too, like UV fluorecence, IR fluorescence just FYI].



So lets look a bit more in detail to these wonderful bright blueish/greenish lighting up pollen, first in visible light...



...then using UV light which stimulates flourescence. These shots need to be done in darkness, since that effect is quite weak and needs long exposure times:




So I hope you enjoyed having a look at a flower using UV induced visible fluorescence!


Stay tuned, more will follow on that fascinating subject...

More info on this very interesting field may be found on my site http://www.pbase.com/kds315/uv_photos