www.photomacrography.net :: View topic - Dabbling with fluorescence on a budget
www.photomacrography.net Forum Index
An online community dedicated to the practices of photomacrography, close-up and macro photography, and photomicrography.
Photomacrography Front Page Amateurmicrography Front Page
Old Forums/Galleries
 
 FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   RegisterRegister 
 ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Dabbling with fluorescence on a budget
Goto page Previous  1, 2, 3, 4, 5, 6  Next
 
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Macro and Micro Technique and Technical Discussions
View previous topic :: View next topic  
Author Message
Lou Jost



Joined: 04 Sep 2015
Posts: 2532
Location: Ecuador

PostPosted: Thu Feb 02, 2017 7:51 am    Post subject: Reply with quote

Chris, theoretically you can diffuse and de-cohere a laser beam by shining it through a colloidal suspension like milk.
_________________
Lou Jost
www.ecomingafoundation.wordpress.com
www.loujost.com
Back to top
View user's profile Send private message Visit poster's website
ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7763
Location: Near London, UK

PostPosted: Thu Feb 02, 2017 9:34 am    Post subject: Reply with quote

Might milk not impart its own colours?
_________________
Chris R
Back to top
View user's profile Send private message
Lou Jost



Joined: 04 Sep 2015
Posts: 2532
Location: Ecuador

PostPosted: Thu Feb 02, 2017 9:49 am    Post subject: Reply with quote

Not unless it flouresces; a monochromatic beam can't change color otherwise.
_________________
Lou Jost
www.ecomingafoundation.wordpress.com
www.loujost.com
Back to top
View user's profile Send private message Visit poster's website
ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7763
Location: Near London, UK

PostPosted: Thu Feb 02, 2017 11:20 am    Post subject: Reply with quote

Certainly but it might fluoresce! And the milk might "go off".
Perhaps gelatin, or grey paint.
A tank of liquid might absorb too much UV, too?
_________________
Chris R
Back to top
View user's profile Send private message
jcb



Joined: 11 Jun 2011
Posts: 43
Location: France

PostPosted: Thu Feb 02, 2017 11:26 am    Post subject: Reply with quote

@Johan : here you are.

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).

Back to top
View user's profile Send private message
harisA



Joined: 03 Jul 2011
Posts: 495
Location: Greece

PostPosted: Thu Feb 02, 2017 11:31 am    Post subject: Reply with quote

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.
Back to top
View user's profile Send private message
Lou Jost



Joined: 04 Sep 2015
Posts: 2532
Location: Ecuador

PostPosted: Thu Feb 02, 2017 12:08 pm    Post subject: Reply with quote

Chris, I don't know about gelatin. The idea is to have biggish diffractors moving around rapidly (relative to exposure time) in water.
_________________
Lou Jost
www.ecomingafoundation.wordpress.com
www.loujost.com
Back to top
View user's profile Send private message Visit poster's website
Lou Jost



Joined: 04 Sep 2015
Posts: 2532
Location: Ecuador

PostPosted: Thu Feb 02, 2017 12:35 pm    Post subject: Reply with quote

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=&esrc=s&source=web&cd=5&cad=rja&uact=8&ved=0ahUKEwj7nsHGkPLRAhUH92MKHR7vDpoQFgg8MAQ&url=http%3A%2F%2Fwww.ksp.kit.edu%2Fdownload%2F1000012434&usg=AFQjCNHOD3V5ZyqfQBPrCK1jqN5zOM_iBQ&sig2=cQ-Sw7j6oW9LAu4j8vZLpA

See Chapter 7. Diluted whole milk is best.
_________________
Lou Jost
www.ecomingafoundation.wordpress.com
www.loujost.com
Back to top
View user's profile Send private message Visit poster's website
ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7763
Location: Near London, UK

PostPosted: Sun Feb 05, 2017 5:02 am    Post subject: Reply with quote

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)
Quote:
“Tamron TT18” objective which has a focal length of 18 mm and a working distance of 9.7 cm.
Hmmm!
_________________
Chris R
Back to top
View user's profile Send private message
ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7763
Location: Near London, UK

PostPosted: Sun Feb 05, 2017 5:48 am    Post subject: Reply with quote

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).
_________________
Chris R
Back to top
View user's profile Send private message
johan



Joined: 06 Sep 2011
Posts: 980

PostPosted: Sun Feb 05, 2017 7:11 am    Post subject: Reply with quote

jcb wrote:
@Johan : here you are.
Thanks, very interesting!
_________________
My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.
Back to top
View user's profile Send private message Visit poster's website
Pau
Site Admin


Joined: 20 Jan 2010
Posts: 4386
Location: Valencia, Spain

PostPosted: Sun Feb 05, 2017 10:06 am    Post subject: Reply with quote

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/viewtopic.php?t=33177
_________________
Pau
Back to top
View user's profile Send private message
ChrisR
Site Admin


Joined: 14 Mar 2009
Posts: 7763
Location: Near London, UK

PostPosted: Sun Feb 05, 2017 11:43 am    Post subject: Reply with quote

Good point, Pau - with Charles' image here, too http://www.photomacrography.net/forum/viewtopic.php?p=204608#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 -?
_________________
Chris R
Back to top
View user's profile Send private message
Pau
Site Admin


Joined: 20 Jan 2010
Posts: 4386
Location: Valencia, Spain

PostPosted: Sun Feb 05, 2017 12:40 pm    Post subject: Reply with quote

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=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwi_-seu2_nRAhXExYMKHUFRDeQQFggjMAE&url=https%3A%2F%2Fwww.insti-fluor.com%2Fcst%2FCSTFluorescenceCourse34.pdf&usg=AFQjCNHFDqgYsWkDOOXjmFzVvfOCZrBx7g

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/questions/9713/why-is-filter-paper-fluorescent
_________________
Pau
Back to top
View user's profile Send private message
enricosavazzi



Joined: 21 Nov 2009
Posts: 1025
Location: Stockholm, Sweden

PostPosted: Sun Feb 05, 2017 12:55 pm    Post subject: Re: Dabbling with fluorescence on a budget Reply with quote

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

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.

Once they arrive, I can make a direct comparison of the two torch models.
_________________
--ES
Back to top
View user's profile Send private message Visit poster's website
Display posts from previous:   
Post new topic   Reply to topic    www.photomacrography.net Forum Index -> Macro and Micro Technique and Technical Discussions All times are GMT - 7 Hours
Goto page Previous  1, 2, 3, 4, 5, 6  Next
Page 2 of 6

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum


Powered by phpBB © 2001, 2005 phpBB Group