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DIC vs Phase contrast. Is the latter one useless?

 
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dennisua



Joined: 31 May 2011
Posts: 98
Location: Kiev, Ukraine

PostPosted: Mon Jul 04, 2011 1:39 am    Post subject: DIC vs Phase contrast. Is the latter one useless? Reply with quote

Hi everyone,

Looking at Photography through microscope I noticed that most amazing pictures are made with DIC and there's very little with Phase contrast. This article suggests that phase contrast is weak in everything except birefrigent subjects http://micro.magnet.fsu.edu/primer/techniques/dic/dicphasecomparison.html
So my question is. Would you guys consider phase contrast useless in imaging live cells (say bacteria division, water microbes, etc.)
DIC is out of the question for financial reasons (also I coulnd't find any that suits my scope) and phase contrast kit is quite affordable here http://store.amscope.com/pct.html
Right now I close condenser diaphragm almost fully to make transparent subjects visible. Diffraction makes them visible but also kills resolution and gives halos around subjects. Example is below:
http://www.youtube.com/watch?v=-nZzYHEA9Fs
Will phase contrast allow for better imaging?
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Cactusdave



Joined: 09 Jun 2009
Posts: 1631
Location: Bromley, Kent, UK

PostPosted: Mon Jul 04, 2011 12:24 pm    Post subject: Reply with quote

No, phase contrast is not 'useless', but it's not DIC either. Phase contrast can give very worthwhile results on subjects of low contast including Protozoa, Rotifers, plankton etc, but the images never have the 'wow' factor of interference contrast techniques. The widespread posting of superb DIC images has perhaps made us too demanding in our expectations of our images. For me the best route to DIC-like images on a budget are the various forms of oblique illumination. These can give very 3D images which approach DIC in their revelation of transparent internal structure at modest or no outlay. If you search 'oblique illumination' on the forum you will find plenty of good examples and methods of achieving oblique effects. If your microscope will accept it, I strongly recommend the Lomo oblique condenser Ol-14, which if used in conjunction with suitable home made slit stops in its filter tray, can achieve remarkably DIC-like images. You may also find useful information on oblique illumination here:
http://www.microscopy-uk.org.uk/dww/articles/oblique.htm
http://www.microscopy-uk.org.uk/mag//artfeb00/pjoblique.html
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dennisua



Joined: 31 May 2011
Posts: 98
Location: Kiev, Ukraine

PostPosted: Tue Jul 05, 2011 2:10 am    Post subject: Reply with quote

Thanks again, Dave.
I'll try oblique illumination on small animals. Seems that it really does offer many interesting effects AND comparatively chep (even free if you cut your own diaphragms). I'm not actually after 3D effect but mostly interested in observing internal structure of transparent subjects. Do you know if it useful for bacteria, living cells internal processes, mitosis observation?
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Cactusdave



Joined: 09 Jun 2009
Posts: 1631
Location: Bromley, Kent, UK

PostPosted: Tue Jul 05, 2011 4:07 am    Post subject: Reply with quote

Oblique illumination is certainly useful for living cells and organisms of low intrinsic optical contrast, I can't speak to its value for very small organisms like bacteria, or for viewing unstained chromosomes during division. Circular oblique illumination is another lighting technique you might consider. You might like to look at this article on using circular oblique illumination (COL) on blood.
http://www.microscopy-uk.org.uk/mag//artmay04/pjblood.html
This is one of a series of articles on circular oblique illumination which can be found linked to it. Commercially made COL stops are available quite cheaply on Ebay.
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dennisua



Joined: 31 May 2011
Posts: 98
Location: Kiev, Ukraine

PostPosted: Tue Jul 05, 2011 6:53 am    Post subject: Reply with quote

Many thanks, Dave!

I somehow missed the whole http://www.microscopy-uk.org.uk/mag/libindex.html part of the site which has vast knowlege on the subject as well as other lightling techniques.
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dennisua



Joined: 31 May 2011
Posts: 98
Location: Kiev, Ukraine

PostPosted: Tue Jul 05, 2011 11:27 pm    Post subject: Reply with quote

Yesterday I tried oblique illumination. I put a piece of cardboard into filter holder (just below the condenser) and by rotating it I was able to do some sort of cresent shaped oblique illumintion. The effect was very impressive. 3D looking terrain with darting ciliates. What's interesting I was able to see waves produced by moving animals. And finally I was able to image the death of a large ciliate that had some sort of bump on it.
Dave, thanks again!


Last edited by dennisua on Wed Jul 06, 2011 12:21 am; edited 2 times in total
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Cactusdave



Joined: 09 Jun 2009
Posts: 1631
Location: Bromley, Kent, UK

PostPosted: Tue Jul 05, 2011 11:53 pm    Post subject: Reply with quote

Pleased to hear you are having some success with oblique illumination. There are many possible variations of the technique and the results can be impressive. It's certainly a lot cheaper than buying a DIC setup. Smile
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