How is this not DIC? Oblique illumination? HOW?

Here you can discuss different microscopic techniques and illumination methods, such as Brightfield, Darkfield, Phase Contrast, DIC, Oblique illumination, etc.
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fibreoptix
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How is this not DIC? Oblique illumination? HOW?

#1 Post by fibreoptix » Sat Aug 11, 2018 1:42 am

Please explain it like I'm 5.
Is there a YouTube video explaining how to do it?


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KurtM
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Re: How is this not DIC? Oblique illumination? HOW?

#2 Post by KurtM » Sat Aug 11, 2018 6:11 pm

Ummm ... why is it not DIC? Certainly looks like DIC to me.
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MichaelG.
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Re: How is this not DIC? Oblique illumination? HOW?

#3 Post by MichaelG. » Sat Aug 11, 2018 6:52 pm

KurtM wrote:Ummm ... why is it not DIC? Certainly looks like DIC to me.
The author's notes read:
Published on 17 May 2014
Aeolosoma sp.

Oblique illumination.
Objective: Plan Achromat 20x
Camera: Sony NEX-5R

'though I'm not sure what that proves.

His other videos are also worth a look.

MichaelG.
Too many 'projects'

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KurtM
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Re: How is this not DIC? Oblique illumination? HOW?

#4 Post by KurtM » Sat Aug 11, 2018 11:39 pm

Got it, thanks -- I didn't mosey over to Youtube the first time around.

I never had any luck getting good effective oblique illumination and crisp clean resolution at the same time, but I have seen where others have done remarkably well. And there's a background gradient in this video that looks like the effect of DIC, but it might be a gradient universal filter? I've seen folks do remarkable well with them too. Either way it's a very nicely done video, that much is for sure.

Gradient Universal Filter: http://www.photomacrography.net/forum/v ... hp?t=15142
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Kurt Maurer
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admin
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Re: How is this not DIC? Oblique illumination? HOW?

#5 Post by admin » Sun Aug 12, 2018 6:02 am

Hello,

I once wrote an article about it, but will also do a video soon:
http://www.microbehunter.com/oblique-illumination/

Oliver
Science may set limits to knowledge, but should not set limits to imagination.
(Bertrand Russell)

billbillt
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Re: How is this not DIC? Oblique illumination? HOW?

#6 Post by billbillt » Sun Aug 12, 2018 1:05 pm

admin wrote:Hello,

I once wrote an article about it, but will also do a video soon:
http://www.microbehunter.com/oblique-illumination/

Oliver
Thanks Oliver for such a clear explanation... I know that oblique appears to perform as DIC, but DIC it is not....

BillT

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Re: How is this not DIC? Oblique illumination? HOW?

#7 Post by GaryB » Mon Aug 13, 2018 11:19 am

I subscribed to his channel a while back. He manages some remarkable depth and if it is oblique, I have no idea how he manages to achieve that look. I've tried a bazillion oblique techniques and none are close to his.
I'd love to know what he does.

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Re: How is this not DIC? Oblique illumination? HOW?

#8 Post by admin » Mon Aug 13, 2018 9:37 pm

Oblique illumination - several points:
1. Not all specimens will produce a good result. To test it, I would try to make leaf-impressions with glue and then observe the glue, because this worked fine for me. White glue on bottom side of leaf, let it dry, peel it off, observe it. Stomata should be visible.
2. Size of patch stop depend on objective used. I would try first to get dark field working well and then block out half to 2/3 of the light on one side.
3. Try to move the condenser left/right (if your microscope allows you to do this).
4. Make sure that the central part of the patch stop blocks out the main light completely.
5. Experimentation is needed but you must make sure that the patch stop really blocks light completely. If you print it on overhead foil, then this might not be dark enough. In this case stack several patch stops.

Links:
http://www.microscopy-uk.org.uk/mag/artjul98/mddic.html

On page 26, it is shown how you can get a DIC effect using photoshop alone:
http://www.microbehunter.com/wp/wp-cont ... 011_12.pdf

Oliver.
Science may set limits to knowledge, but should not set limits to imagination.
(Bertrand Russell)

Tom Jones
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Re: How is this not DIC? Oblique illumination? HOW?

#9 Post by Tom Jones » Tue Aug 14, 2018 2:39 am

He explains his technique in the comment section of another video: https://www.youtube.com/watch?v=7xvkEssi-Ss

He doesn't use a patch stop, but de-centers the Abbe condenser, and sometimes uses a Raynox DCR-250 macro lens sitting on top of the illumination port.
Oblique effect is obtained by condenser only, you don't need anything else. No stops, no other attachments, just mentioned condenser and optionally Raynox lens. Steps are almost the same as for Koehler illumination. After proper Koehler settings you have to de-center condenser (off optical axis), and then play with condenser's iris diaphragm, field iris diaphragm and with vertical position of condenser.
He seems to have the technique down pretty well!

Tom

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fibreoptix
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Re: How is this not DIC? Oblique illumination? HOW?

#10 Post by fibreoptix » Tue Aug 14, 2018 2:56 am

He should do a video on it.

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Re: How is this not DIC? Oblique illumination? HOW?

#11 Post by RobBerdan » Sun Dec 09, 2018 9:25 pm

Oblique illumination can often be achieved by simplying having a filter tray under the condenser partlially blocking the light, one can also use various shaped filters below the condenser - these filters can be made with a sheet of glass and black tape or other opaque material cut in various shapes. I have experimented with many of these and sometimes certain subjects will resemble DIC in oblique lighting but they never look as good as DIC in my opinion. Oblique lighting costs next to nothing whereas DIC can cost thousands of dollars to add so its just not affordable for most folks unless one gets lucky to find a good used DIC microscope. Still Rheinberg lighting, Oblique illumination and Darkfield lighting can result in some stunning photos and these can be added to any light microscope cheaply using coins, darkfield filters and Rheinberg filters available for sale on E-bay for about $30. .

I posted some information on Rheinberg, Oblique, Hoffman Modulation, Positive and Negative Phase contrast here:
https://www.canadiannaturephotographer. ... s2017.html if interested.

I also find it valuable to experiment with the "wrong" settings using phase contrast rings, or my condensor and also combing different types of lighting e.g. Rheinberg and Darkfield can sometimes produce interesting results. Also polarizing filters, wave plates (or scotch tape, saran wrap) can add interference colours. If you have a microscope and have mastered the basics its great to explore new ideas. I read a science paper on how to convert a light microscope to perform optical diffraction using a small pin hole - and it worked.
Attachments
Cladoceran Darkfield illumination
Cladoceran Darkfield illumination
rberdan_14.jpg (113.33 KiB) Viewed 3873 times
Wrong Phase ring - created a sketch like effect on my Axioscope
Wrong Phase ring - created a sketch like effect on my Axioscope
PhaseI_20X_DSC_0285.jpg (262.05 KiB) Viewed 3873 times
DIC illumination
DIC illumination
DSC_0271.jpg (159.16 KiB) Viewed 3873 times
Oblique illumination
Oblique illumination
rotifer_DSC_0210.jpg (111.73 KiB) Viewed 3873 times
Rheinberg
Rheinberg
DSC_0757.jpg (293.83 KiB) Viewed 3873 times

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