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Food under UV Induced Fluorescence

Fluorescence
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#21 Damon

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Posted 03 January 2015 - 23:00

Oh ok.
So a wavelength can't induce it's own wavelength?

#22 Damon

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Posted 03 January 2015 - 23:38

I didn't think my Blak-Rays produced an IR at all.
Or if they do, it was filtered by the glass.

Edited by Damon, 03 January 2015 - 23:39.


#23 baffe

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Posted 03 January 2015 - 23:40

Oh it can induce it's own wavelength. Some lasers use that effect.

But in that case you will not be able to separate induced fl from pumping energy. Both have the same "colour" but the induced is always smaller in amount.

And if you separate them by the time delay between pumping energy in and monitoring the light coming out then it is phosphorescence per definition.

But this could make beautiful pictures too!

(I read that there is also a "spin criterion" to define fl but I read without understanding that)

#24 baffe

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Posted 03 January 2015 - 23:43

The filter glass on my BL cuts vis, but is transparent for both IR and UV. The glass is similar to UG11

#25 Damon

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Posted 04 January 2015 - 01:16

Thanks for the info. I am beginning to understand that now.

Re:Blak-Rays--
Oh your right. At least for now though, it seemed I didn't need to worry about IR as my lens and camera/sensor are unmodified thus blocked the IR. (although Andrea is becoming skeptical so I better get a filter soon).

-D

#26 Damon

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Posted 04 January 2015 - 03:19

Hots Dogs - yummy


Next time you are at a barbecue and your friend says "hey you gettin' in on a couple of these dogs or what?" -- remember these photos.

Visible: Canon 30D Unmodified, Canon EF24-105mm f/4L IS USM, Incandescent light, .6 s @ f/11 ISO 320, No Filters.
Attached Image: Hot Dogs_Visible light©DNoe_resize.jpg



I put a piece of egg shell in there to use as white balance FWIW
UVIVFL: Canon 30D Unmodified, EF24-105mm f/4L IS USM, 2 Blak-Rays ML-49, 30 s @ f/11 ISO 320, No Filters.
Attached Image: Hot Dogs_UVIVFL©DNoe_resize.jpg


Diptych
Attached Image: Hot Dogs©DNoe_resize.jpg



Just a note: I tried a different Blak-Ray with this pic that has a really wide throw. They show the same color to my eyes as my B100AP's but they also show more purple on the surface of some things.



-D

#27 colinbm

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Posted 04 January 2015 - 03:35

If you are going to keep doing this Damon, you could improve on your house-keeping skills ?
"I tried a different Blak-Ray" ?? What different Blak-Ray please ?
Col

#28 Damon

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Posted 04 January 2015 - 04:08

If you are going to keep looking at these things, could you improve on your reading skills?

It's in the description of my equipment above each photo, every time I post.

:P :lol: :lol:

-D

#29 colinbm

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Posted 04 January 2015 - 04:20

READ....that is only for eggucated people.....I just look at the pictures....they say a picture is worth a thousand words, so I don't waste my time with all that black scratchy stuff on the page :P
Col

#30 Damon

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Posted 04 January 2015 - 04:54

You are not as egg headed as I once thought.

I think the ML-49's are going to be great for walking around outside with. They will supposedly last 20 hours or so and are @365nm. I am quickly becoming bothered by the purple from the fluorescent bulb when associated with picture taking. The hot dogs looked identical with the ML's and the B100AP's but some stuff gets a purple cast that I am not liking.
So most likely, I will relegate the 2 I have to field searching. They seem to fluoresce everything the B100AP's do, which they should. So that much I like. Perhaps I can wander with those and collect stuff and then use the AP's for photography. It's a work in progress. You don't know for sure unless you try it yourself.

-D

#31 colinbm

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Posted 04 January 2015 - 05:53

That is interesting that you are finding the ML-49 useful, I had thought they would have been as useful as an ash tray on a motor bike.
Magenta isn't in the rainbow either, & I wish it would keep out of my photos too.
Col

#32 baffe

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Posted 04 January 2015 - 08:24

Damon I use the IR-filter inside the cam like you do.

It usually works.

#33 baffe

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Posted 04 January 2015 - 08:51

My blackrays (left 125W right 21W) 1/100s ISO400 aperture for full f5.6 for IR f4:

FullSpectrum:
Posted Image

With Tokina R72 IR Filter:
Posted Image

Seems to me like they make more IR than UV!

Edited by baffe, 04 January 2015 - 09:04.


#34 colinbm

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Posted 04 January 2015 - 09:23

Lots of visible too Stefan, but yes too much IR.
Col

#35 baffe

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Posted 04 January 2015 - 09:32

VIS is not that much. May seem so, but the glass door (2x2m) left the beamers was not covered/closed and there was some daylight from outside.

In my opinion big problem is IR, not VIS !

But the HM usually manages that if one doesn't use a fullspec cam.

#36 colinbm

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Posted 04 January 2015 - 09:45

Yes, depending on what you want to do with them. The Baader U2 & the Schott S8612 do a good work at eliminating the IR from reaching the cameras sensor..
Col

#37 Shane

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Posted 04 January 2015 - 17:15

[quote]Is there such a thing as UV-induced UV Fluorescence?[/quote]
Yes, for example 365nm UV excitation can cause 390nm emission in some diamonds.

[quote]Is there such a thing as Visible-induced IR fluorescence?[/quote]
Yes, typically blue light and less likely green light and even more unlikely red light.
I have recorded blue excitation/IR emission in some gem materials,
In addition, your eggs shells are fluorescing red due to porphyrins and are also emitting IR as a result of porphyrin excitation.
Plant leaves also exhibit this. I used to have am emission spectrum of a geranium leaf on my website but only visible by direct link which my current security is blocking so I will try and repost it.

[quote]--darkness thus not required--could be in full sun?[/quote]
It occurs but it is too weak, with respect to reflectance, to be recorded without darkness.

[quote](I read that there is also a "spin criterion" to define fl but I read without understanding that)[/quote]

You are referring to the singlet and triplet spin states of fluorescence and phosphorescence. However, the definitions only apply in certain scientific circles. You will notice that the time scale for triplet spins states is in fractions of a second. For UV excited phosphorescence, this basically means that phosphorescence would cease to occur fractions of a second after turning of the UV source. Most of us have observed that "phosphorescence" (as used by the community in general) can last seconds, minutes (typical household fluorescent tubes) and even hours and days. In many cases this type of "phosphorescence" is most likely room temperature thermoluminescence, where the electron traps are emptied slowly by ambient the temperature.

Did some interesting experiments in the past that involved heating samples in darkness to empty the electron traps, then cooling to -180C and allowing the sample to come to room temperature while recording any luminescence emission (which was none) then repeating the experiment but filling the empty traps with UV at -180C. In the latter case the samples in question would often emit several different colours as temperature slowly increased. The different colours were a result of different electron trap "depths" that require different temperature to empty them. In some circles the emission would be referred to as phosphorescence but it clearly is thermoluminescence.

#38 Shane

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Posted 04 January 2015 - 17:19

Geranium leaf porphyrin fluorescence exhibiting IR emission.
Ignore the incorrect y-axis title.

Attached Images

  • Attached Image: Geranium leaf-nolink.jpg

Edited by Shane, 04 January 2015 - 17:20.


#39 Damon

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Posted 04 January 2015 - 19:01

Pretty neat & interesting stuff there Shane.

So the above graph is IR fluorescence?
What was the source of light that caused this?
Could this be caught on a proper camera?


Thanks,
-D

#40 Shane

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Posted 05 January 2015 - 01:49

Yes this is IR fluorescence excited by blue-green light centered around 490nm but UV works just as well for porphyrins, in this case chlorophyll.
So basically the excitation was selected for an approximation of the solar emission maxima for a standard solar spectrum.

This can easily be photographed using a broad band modified digital camera with the appropriate filters.