First attempt with DIY polarization - Help needed

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Javier
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First attempt with DIY polarization - Help needed

#1 Post by Javier » Sun Sep 11, 2022 2:44 am

Today I did my first attempt with DIY polarization technique. I found a little snail with a colony of Peritrich CIliates attached to it. This technique is absolutely beautiful to observe through the eyepieces, but quite demanding for the camera in terms of dynamic range and for the illumination systems in terms of power. The 1W LED of my scope is not up to the task for taking videos, but it works OK up to 200 x and decently up to 400 x for observation.

I'm somehow confused about how to use the condenser aperture diaphragm, leaving it wide open causing poor contrast but closing it seems to be detrimental for the polarization effect. Any tips on this regard?

Also, is there a way to evaluate the amount of polarization used? Is a matter of taste or are there some guides on this aspect depending on the specimen?

Thanks in advance,
Javier.

Video: iPhone 5s through Amscope C 120b - DIY polarized light using two lunar variable polarization filters.


PeteM
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Re: First attempt with DIY polarization - Help needed

#2 Post by PeteM » Sun Sep 11, 2022 3:59 am

Three thoughts:

1) High quality polarizers - which go to near complete extinction when crossed and have good transmission when aligned - make a significant difference. Cheap camera polarizers can work with highly birefrigent specimens - noting that the circular ones need to be oriented properly. But better results can be had.

2) Not sure where you placed your polarizers, but getting them away from any of the image planes where dust or defects might show up is is a good idea. And while bare polarizing sheet film will work, an optically flat polarizer (sandwiched between glass) provides better contrast in my experience.

3) As you've already noticed, polarization (along with phase contrast, darkfield, DIC, and image-stopping camera speeds) is a good reason to buy or retrofit a scope so it provides enough illumination.

Phill Brown
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Re: First attempt with DIY polarization - Help needed

#3 Post by Phill Brown » Sun Sep 11, 2022 11:03 am

IMG-20220815- WA0001.jpg
Image of sand grains.Great to see DIY polarization,looks like you are using complete CPL which will only go to a deep blue unless you use a DF patch. It's also possible to misalign the patch or condenser to give a range of effects that doesn't effect the budget.
Linear polarization will go to extinction showing birefringent material only on a black background.
1w LED is the only real issue,I have a Chinascope with 3W neo LED that just about cuts it in DF with CPL below and above oriented to blue background.
20w halogen is enough for moving subjects, infrared filter will stop a drop of water boiling with 30w+ halogen.
CPL will still work with phase which is why I have no wish to go to DIC.
Introducing a layer of acrylic on top of the lower filter should give any choice of background colour.
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Javier
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Re: First attempt with DIY polarization - Help needed

#4 Post by Javier » Sun Sep 11, 2022 1:46 pm

Thank you, Pete and Phill.

I really don' know much about the quality of these filters. For the video I used a Cozo Japanese one, and one from a lunar variable polarizer that I bought specially to do this technique because of the size needed to mount on the head of the scope (images attached). I haven't experienced problems with the power of the 1 W LED previously doing light and dark field, but this is more challenging... will see.
Phill Brown wrote:
Sun Sep 11, 2022 11:03 am
looks like you are using complete CPL which will only go to a deep blue unless you use a DF patch
I' m so glad you posted this. It seems that the Japanese filter is CPL (I assume this is circular polarization) and combined with the linear polarized filter of the lunar variable gives that deep blue. I just checked how the two lunar polarizers interact and they go to full black extinction, rather than the dark blue. This is very interesting, it is nice to have different options. I will post videos using the two different combination on this thread.
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Last edited by Javier on Sun Sep 11, 2022 3:00 pm, edited 5 times in total.

Javier
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Re: First attempt with DIY polarization - Help needed

#5 Post by Javier » Sun Sep 11, 2022 1:52 pm

By the way, the video is at 100 x and 200 x. The lack of detail and contrast of the Peritrich Ciliates seems to be because they were not reactive to the polarized light. There was a shiny Hypotrich that I couldn't record because it got under the snail, and I had to return the sample to the jar because I didn't want the poor snail to die under the coverslip.

Phill Brown
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Re: First attempt with DIY polarization - Help needed

#6 Post by Phill Brown » Sun Sep 11, 2022 3:04 pm

I should have added the filter above objective is the analyser, I wouldn't expect best results from plastic film as it scratches easily.
Leaving dust or residue on glass isn't best practice, under the head should be low maintenance.

Javier
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Re: First attempt with DIY polarization - Help needed

#7 Post by Javier » Sun Sep 11, 2022 6:42 pm

The one on the head is also glass, ther is no plastic on the optical path.

Javier
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Re: First attempt with DIY polarization - Help needed

#8 Post by Javier » Mon Sep 12, 2022 10:20 pm

1W LED is really a problem for this technique... specially when the polarizers are fully crossed. Looking nice on visual though...


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imkap
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Re: First attempt with DIY polarization - Help needed

#9 Post by imkap » Mon Sep 12, 2022 10:25 pm

Looks great, no doubt you'll make it even better. I still don't understand how it works exactly, but I'll examine the matter soon... :D

Javier
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Re: First attempt with DIY polarization - Help needed

#10 Post by Javier » Mon Sep 12, 2022 10:30 pm

imkap wrote:
Mon Sep 12, 2022 10:25 pm
Looks great, no doubt you'll make it even better. I still don't understand how it works exactly, but I'll examine the matter soon... :D
Thank you! I don't think I'll be able to make it better this time, light intensity is a real limitation for this technique and videos turn noisy and with low resolution. But hey, this is a 250 dollars scope...

How it works optically? I'll let some one else explain it to you :lol:

Phill Brown
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Re: First attempt with DIY polarization - Help needed

#11 Post by Phill Brown » Tue Sep 13, 2022 12:55 pm

A great example of why I haven't sunk a medium sized fortune into DIC.
Considering a used 160mm setup from Nikon or Olympus can be had for not much more.
I've only got this type of setup to work well as far as x45 .65na with a 1.5 head, Using a 14x eyepiece projected onto an APS C.
I'm lucky enough to have a lathe so no sticky tape needed.
Stray light at the camera end is suboptimal, phone cameras don't seem to mind it so much.

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essence25
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Re: First attempt with DIY polarization - Help needed

#12 Post by essence25 » Sat Oct 15, 2022 4:56 am

Wow amazing! If I want to do this to my newly acquired Eclipse E200 MV LED MV R, with best possible option of polarizers where do I buy them and what exactly do I need?

On another note, at my local Science and Surplus store I saw set of LOMO glass polarizers and set of LOMO DIC Prisms.
$19 each for polarizers top/bottom and $50 DIC prisms each upper and lower.
I could probably pop out the polarizers from their LOMO holders if those would be good to use.
What can i do with those LOMO DIC prisms in my Eclipse scope?

Phill Brown
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Re: First attempt with DIY polarization - Help needed

#13 Post by Phill Brown » Sat Oct 15, 2022 9:49 am

I got 27mm CPL filters from eBay but recently not found any 27mm available.
The space under the head is limited diameter for the analyser.
Can't help with the DIC conversion but I would imagine it's a precision engineering job that won't get complicated due to some incompatible parts.

Javier
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Re: First attempt with DIY polarization - Help needed

#14 Post by Javier » Sat Oct 15, 2022 2:24 pm

essence25 wrote:
Sat Oct 15, 2022 4:56 am
Wow amazing! If I want to do this to my newly acquired Eclipse E200 MV LED MV R, with best possible option of polarizers where do I buy them and what exactly do I need?

On another note, at my local Science and Surplus store I saw set of LOMO glass polarizers and set of LOMO DIC Prisms.
$19 each for polarizers top/bottom and $50 DIC prisms each upper and lower.
I could probably pop out the polarizers from their LOMO holders if those would be good to use.
What can i do with those LOMO DIC prisms in my Eclipse scope?
I guess every scope is different. I'm using lunar variable polarization filters. One is permanently mounted on the head of the scope and I just put the other over the lamp of the scope.

I think this video from "microuruguay" might be useful for you:

https://www.youtube.com/watch?v=Z4ukQMTBeB8

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