Dabbling with fluorescence on a budget
Moderators: rjlittlefield, ChrisR, Chris S., Pau
@Johan : here you are.
Some theory first :
As you see, no light passes through both filters superimposed.
The setup is basic. Having a white background helps to identify possible problems : if you see the background in the picture you are not photographing luminescence...
Here is the result (Gloiocladia_repens).
Some theory first :
- the blue line is the transmission of the blue Lee 721 filter
the red one the transmission of the Heliopan red R25 filter
the green solid lines are the wavelengths that excite the chlorophylle
the dotted green lines the luminescence wavelengths
As you see, no light passes through both filters superimposed.
The setup is basic. Having a white background helps to identify possible problems : if you see the background in the picture you are not photographing luminescence...
Here is the result (Gloiocladia_repens).
This is a photo of the nichia led.
From the following link:
http://www.nichia.co.jp/en/product/uvled.html#NVSU333A
the only that matches is NCSU276A u365 at the middle of the page
typical optical power 780mw at 500ma.This is a yield of aprox 35%.Rather amazing i would say.
From the following link:
http://www.nichia.co.jp/en/product/uvled.html#NVSU333A
the only that matches is NCSU276A u365 at the middle of the page
typical optical power 780mw at 500ma.This is a yield of aprox 35%.Rather amazing i would say.
Here is everything anyone would ever want to know (and more!) about using milk to reduce laser speckle patterns below the threshhold of human vision:
https://www.google.com/url?sa=t&rct=j&q ... Au4j8vZLpA
See Chapter 7. Diluted whole milk is best.
https://www.google.com/url?sa=t&rct=j&q ... Au4j8vZLpA
See Chapter 7. Diluted whole milk is best.
Has to be homogenised. apparently!
I'm aware milk, gelatin, and Dettol are used, it's the spectral behaviour I queried.
The article doesn't mention fluorescense. Best would be to try it. Also UV may get absorbed somewhere.
I did find (P88)
I'm aware milk, gelatin, and Dettol are used, it's the spectral behaviour I queried.
The article doesn't mention fluorescense. Best would be to try it. Also UV may get absorbed somewhere.
I did find (P88)
Hmmm!“Tamron TT18” objective which has a focal length of 18 mm and a working distance of 9.7 cm.
Chris R
The laser was informative - I read, that in discussion of chlorophyll spectra
fluorescence spectra are invariate, and the same spectrum will be obtained regardless of which wavelengths are used for excitation:
I don't think that's entirely true, particularly in terms of amplitude, but with that in mind, these pop up in the first few Google hits::
and
and
Therefore, "about 405nm" leds are useful, because they're short without being too dangerous.
They provide spectral separation for either
filtering out the excitation colour from the light reflecting off the subject, or
filtering out the emission colour from the light hitting the specimen.
Chlorophyll in living plants, doesn't have exactly the same spectrum as in solution (such as ethanol).
Also, in the plant, there is a quenching effect. After first exposure to the excitation, the level of emission drops (Kautsky curve).
fluorescence spectra are invariate, and the same spectrum will be obtained regardless of which wavelengths are used for excitation:
I don't think that's entirely true, particularly in terms of amplitude, but with that in mind, these pop up in the first few Google hits::
and
and
Therefore, "about 405nm" leds are useful, because they're short without being too dangerous.
They provide spectral separation for either
filtering out the excitation colour from the light reflecting off the subject, or
filtering out the emission colour from the light hitting the specimen.
Chlorophyll in living plants, doesn't have exactly the same spectrum as in solution (such as ethanol).
Also, in the plant, there is a quenching effect. After first exposure to the excitation, the level of emission drops (Kautsky curve).
Chris R
Thanks, very interesting!jcb wrote:@Johan : here you are.
My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.
As you can see in the graphs (and my very limited experience agrees) the best red fluorescence of chlorophyll can be obtained around 450nm, a royal blue 450-455nm Cree XT-E is my most adequate light excitation source for it.
UV has the big advantage of providing blue fluorescence of cell walls like for example at the delightful Jacek's last images here:
http://www.photomacrography.net/forum/v ... hp?t=33177
UV has the big advantage of providing blue fluorescence of cell walls like for example at the delightful Jacek's last images here:
http://www.photomacrography.net/forum/v ... hp?t=33177
Pau
Good point, Pau - with Charles' image here, too http://www.photomacrography.net/forum/v ... 608#204608 .
Next question, If we use 365nm to excite, is a 420nm long pass filter better than say a 400nm?
What is it in the walls which fluoresces blue, and at what wavelength? Something over 450nm I would guess -?
Next question, If we use 365nm to excite, is a 420nm long pass filter better than say a 400nm?
What is it in the walls which fluoresces blue, and at what wavelength? Something over 450nm I would guess -?
Chris R
The devil is in the details, in principle 400nm or 420nm emission filters will work equally well for blue emission with 365nm excitation IF you actually use excitation radiation no longer than 400nm and the filter is perfect.
If you use the adequate excitation filter as I do with my filter cubes it is but in Charles setup without excitation filter the violet tail of the LED emission can obscure fluorescence, so the longer emission filter is much more adequate.
I've just ordered a Nichia UV NVSU233A-D1 365nm. When received and mounted I will be able to test it, at the moment my UV LEDs aren't adequate for this test.
This is a table fom a paper I downloaded*
https://www.google.ca/url?sa=t&rct=j&q= ... vfOCZrBx7g
So likely that blue fluorescence comes from cutin or lignin, more likely from cutin in epidermic cells
Cellulose is not fluorescent at this wavelength
http://chemistry.stackexchange.com/ques ... luorescent
If you use the adequate excitation filter as I do with my filter cubes it is but in Charles setup without excitation filter the violet tail of the LED emission can obscure fluorescence, so the longer emission filter is much more adequate.
I've just ordered a Nichia UV NVSU233A-D1 365nm. When received and mounted I will be able to test it, at the moment my UV LEDs aren't adequate for this test.
This is a table fom a paper I downloaded*
https://www.google.ca/url?sa=t&rct=j&q= ... vfOCZrBx7g
So likely that blue fluorescence comes from cutin or lignin, more likely from cutin in epidermic cells
Cellulose is not fluorescent at this wavelength
http://chemistry.stackexchange.com/ques ... luorescent
Pau
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Re: Dabbling with fluorescence on a budget
I just ordered two of these because they are extremely cheap (right now 50% discount according to the web site, although this seems to be the same for many other items on the site) compared to the MTE UV torches that probably use the same or similar LEDs (I think I paid about 250 US$ for one a few years ago). If they turn out to have a comparable UV emission, these new ones are a real bargain. In fact, they are even cheaper than the retail price for one of these LEDs from some online EU sources.Charles Krebs wrote:When I came across some relatively inexpensive flashlights with Nichia 365nm UV LEDs I decided to give it a try. These are the flashlights:
(picture)
They were purchased from this site:
http://www.gearbest.com/led-flashlights/pp_277704.html
Once they arrive, I can make a direct comparison of the two torch models.
--ES