Re: Numerical aperture and spatial resolution

Posted by Zdenek Svindrych-2 on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Numerical-aperture-and-spatial-resolution-tp7591293p7591299.html

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Hi George and Javier,

regarding aperture and resolution of DSLR (actually mirror-less) I put some
photos together here:
https://drive.google.com/file/d/1vDYqDBPgapZYad3JahRm8R5W5Bkwu4T6
But, it will only work with some lenses (well, with most, but not in the
full F-stop range), and only with some cameras (more pixels is better here,
kind of an exception :-).

Davide, the Evenett's video is great! Many demonstrations were quite
surprising, and I have nothing to add to it (maybe a note, that the phase
contrast method in all its simplicity still yielded Zernike a Nobel prize!).
But even though one thought follows from another nicely, at the end if you
ask your students "So why does higher NA mean higher resolution?" they'll
say "Well, uhm..." It's not very likely they'll gain a deeper understanding
of how all these concepts fit together.

Good luck!

zdenee

On Sat, Sep 19, 2020 at 12:25 PM George McNamara <[hidden email]>
wrote:

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>
> Hi Javier,
>
> I suggest you ask the class if they have any interest in taking photos
> with their smartphone or DSLR camera, and if they do, bring in a DSLR
> and tripod and computer/projector (if the room does not have that
> already), explain f/stop and NA are inverse of each other, and
> demonstrate NA (resolution, intensity, depth of field) on the class by
> focusing on faces in the middle row. Wavelength: yes, you could buy some
> filters for the camera lens (or deal with separating channels in
> Photoshop, fiji ImageJ, etc), but probably better done on a microscope.
>
> George
>
> p.s. this post was inspired by a conversation yesterday -- Friday happy
> hour -- with a colleague, Prof. Jim Potter, who told me about a
> conversation he had with someone with a very expensive digital camera
> hobby, who only used their cameras set to auto. Jim explained f/stop,
> ISO and more (framing scene etc). My thanks to Jim for good story with
> nice timing and especially foraging for the beverages.
>
> A fun (in theory, but probably not practical or wise) wavelength test
> would be to use bring in blue (~400 nm) and NIR (~800nm would be nice,
> values chosen to be 2 fold, not necessarily practical) and a smoke
> machine (and some 400nm and NIR friendly lighting in case room lights
> too dim at those wavelength), and demonstration resolution vs ability to
> see through the smoke (Mie scattering etc). If you do this, and the
> smoke alarm turns on, your school may not be happy with you (though all
> the students may be happy to escape class early).
>
> Of course if they vote no to learning about f/stop and NA, you can ask
> them how they expect to get to a million TikTok followers each without
> knowing how to take good quality videos. Come ot think of it, if they do
> vote yes, and you put your demo on your TikTok feed and make a lot of
> money, you can send me the URL and a thank you check.
>
> On 9/19/2020 5:38 AM, F Javier Diez Guerra wrote:
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > Hello,
> >
> > I wonder if anybody in the list could help.
> >
> > I want to convey to biology undergraduate students (very allergic to
> > physics and mathematics) the understanding of the relationship between
> > numerical aperture and spatial resolution.
> >
> > I have already given them links to the different microscopy primer
> > sites. They find difficult to understand why the airy disk is
> > generated in the image plane, how the diffraction orders affect
> > resolution and why increasing NA reduces the image spot.
> >
> > Could anybody share a basic and intuitive infographic slide, animation
> > or any other resource that could help to ease comprehension in this
> > context?
> >
> > Thanks
> >
> > Javier
> >
> >
>


--
--
Zdenek Svindrych, Ph.D.
Research Scientist - Microscopy Imaging Specialist
Department of Biochemistry and Cell Biology
Geisel School of Medicine at Dartmouth