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PostPosted: Mon Jun 11, 2018 7:50 am 
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Diatom Sample at 640X (40X Objective x 16X Eyepieces)
Single shot, Crop and Adjust Contrast / Brightness

Diatom was wet mount, but the surrounding water was dry up, some small drop can be seen in the photo.

The 40X Objective work well for Oblique Illumination.
The 16X Eyepieces magnify a little more than 10X Eyepieces, so small details can be seen easier.



Suphot


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PostPosted: Mon Jun 11, 2018 12:31 pm 
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Nice detail in that image!
Did you get a chance to measure it?
One of the nice things about oblique is that it lets you use most if not all of the NA of the objective.

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PostPosted: Mon Jun 11, 2018 3:57 pm 
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Great image!... Oblique attempts to mimic DIC, and this one approaches that.. It does not have the perfectly crisp outline that makes DIC shine, but great pic... Thanks for sharing...


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PostPosted: Thu Jun 14, 2018 6:48 am 
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Thank you very much for your comment 75RR and billbillt,


75RR, I have not a chance to measure it, the Oblique illumination look 3 dimensions to me especially the small water drop near diatom.


billbillt, Yes, I like the effect and it look like DIC in some degree, for 40X Objective.



Suphot


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PostPosted: Thu Jun 14, 2018 7:44 am 
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billbillt wrote:
Great image!... Oblique attempts to mimic DIC, and this one approaches that.. It does not have the perfectly crisp outline that makes DIC shine, but great pic... Thanks for sharing...


Shouldn't that be DIC mimics oblique? It must predate it by about a hundred years.


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PostPosted: Thu Jun 14, 2018 12:46 pm 
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photomicro wrote:
billbillt wrote:
Great image!... Oblique attempts to mimic DIC, and this one approaches that.. It does not have the perfectly crisp outline that makes DIC shine, but great pic... Thanks for sharing...


Shouldn't that be DIC mimics oblique? It must predate it by about a hundred years.



QUITE POSSIBLE.. BUT THE IMAGE QUALITY DOES NOT REACH THE LEVEL OF DIC.. IF A PERSON HAS DIC THERE IS NO REASON TO USE OBLIQUE..


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PostPosted: Thu Jun 14, 2018 1:30 pm 
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Bonjour
Jolie images en éclairage oblique.
Pour réaliser un beaux éclairage oblique il faut plus ou moins jouer avec le cache en carton ou plastique pour avoir plus ou moins effet rechercher.
Car suivant la nature de objet on régleras le cache en plastique pas de la même façon.
Celui que j'utilise le plus et la flèche de Mathias.
http://www.microscopies.com/DOSSIERS/Ma ... ATHIAS.htm
Elle permet avoir différent type éclairages et ça réalisation et facile à réaliser.
Cordialement seb

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PostPosted: Mon Jul 09, 2018 9:53 am 
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billbillt wrote:
photomicro wrote:
billbillt wrote:
Great image!... Oblique attempts to mimic DIC, and this one approaches that.. It does not have the perfectly crisp outline that makes DIC shine, but great pic... Thanks for sharing...


Shouldn't that be DIC mimics oblique? It must predate it by about a hundred years.



QUITE POSSIBLE.. BUT THE IMAGE QUALITY DOES NOT REACH THE LEVEL OF DIC.. IF A PERSON HAS DIC THERE IS NO REASON TO USE OBLIQUE..



Fair point Bill, though I often wonder how much of this is due to how much it has cost! Of course that doesn't stop lots of us wanting it.

I add my own image here...but not what method.

Mike


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PostPosted: Sat Jul 14, 2018 2:54 am 
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Thank you very much for all comments and sharing your opinion.

The photo from photomicro was very sharp and clear. You may share more information about your set up and illumination technique.


Suphot


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PostPosted: Mon Jul 16, 2018 8:54 pm 
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Suphot wrote:
Thank you very much for all comments and sharing your opinion.

The photo from photomicro was very sharp and clear. You may share more information about your set up and illumination technique.


Suphot


It is taken using a x20 objective, and using VAC, which is Variable Asymmetrical Contrast, after Arthur Strange (his two articles are 1987 and 1989 but not particularly practical in nature). It involves making a disc using polarising material to put in the condenser, and thus can be used with most of your normal objectives, and costs very little. For the amateur it is well worth setting up for any or all of your microscopes in my opinion.

Mike


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PostPosted: Thu Jul 19, 2018 4:14 am 
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Thank you very much Mike,

I don't know about Variable Asymmetrical Contrast before. It look very good in your photo. I have to find the polarize sheet to try this one. You may post your photo from this technique some more.

The Oblique illumination that I used, came from GUF Filter or Offset my Dark field patch to create Oblique. The Variable Asymmetrical Contrast is the next one to try.


Suphot


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PostPosted: Thu Jul 19, 2018 4:41 am 
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I tried finding info on VAC without luck, just a couple of photos. I'd love to know how to set it up.


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PostPosted: Thu Jul 19, 2018 9:14 am 
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photomicro wrote:
billbillt wrote:
photomicro wrote:

Shouldn't that be DIC mimics oblique? It must predate it by about a hundred years.



QUITE POSSIBLE.. BUT THE IMAGE QUALITY DOES NOT REACH THE LEVEL OF DIC.. IF A PERSON HAS DIC THERE IS NO REASON TO USE OBLIQUE..



Fair point Bill, though I often wonder how much of this is due to how much it has cost! Of course that doesn't stop lots of us wanting it.

I add my own image here...but not what method.

Mike

This is excellent and easily up there with ridiculously expensive and cumbersome DIC. The fact that it can be used with most existing objectives further elevates it beyond DIC as far as I am concerned.

Great photograph!

I see that many prize winning photomicrographs have used VAC, this one by Spike Walker, awarded Third Prize in Spot on Micro Competition 2015

Image

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PostPosted: Thu Jul 19, 2018 9:21 am 
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GaryB wrote:
I tried finding info on VAC without luck, just a couple of photos. I'd love to know how to set it up.



Here's a link to VAC from the old forum

http://www.microbehunter.com/forum/specimens-samples-and-slides/arthur-stranges-variable-amplitude-contrast-method-vac-2/

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PostPosted: Thu Jul 19, 2018 9:24 am 
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IanW - with/WITHOUT ridiculously expensive.....?
Also, may I add that DIC was invented for the sake of specimens, like living cells in culture, for which oblique would be inadequate.

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PostPosted: Thu Jul 19, 2018 9:50 am 
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Hobbyst46 wrote:
IanW - with/WITHOUT ridiculously expensive.....?

To clarify: it is up there with DIC but without using it:-)

"Also, may I add that DIC was invented for the sake of specimens, like living cells in culture, for which oblique would be inadequate."


Yes it does a great job at that - shame about the cost to the amateur. Still most of the fun is to be had in finding ways of doing more with less:-)

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PostPosted: Thu Jul 19, 2018 11:30 am 
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I see that IanW has given a reference to a short discussion elsewhere on the forum.

The original articles by Strange are;

1. Strange, A., New Developments in Variable Asymmetrical Contrast Microscopy. MICROSCOPE 1989 (37) p355-376.
2. Strange, A., Variable Asymmetrical Contrast Microscopy. MICROSCOPE 1987 (35) p279-290.

Unfortunately, whilst I have photocopies of these, I do not find them all that useful, as they give very little practical detail of how to do this with your stand, if at all.

Mr B Wilkinson, in the UK took up this technique, and demonstrated it at meetings in the UK over a period of years, and it was well received. I persuaded him in 2011 to write up his methods, with full practical details, which appeared in the April issue of 'Balsam Post' the journal of the Postal Microscopical Society. This ten page article showed how to adapt the technique to a number of stands, namely using a Zeiss standard Abbe on an LCE, and phase 'turret' type condensers on Zeiss West and Reichert stands. Advice is given on cutting the discs, their size for named objectives, where to put them, and how to tweak the effect. There was also a follow-up article by Mr Wilkinson, and another by Mr Chaplin showing how he fitted his Biolam (Russian LOMO) stand for this.

Unfortunately, the PMS website (https://postalmicroscopicalsociety.github.io/index.html) does not include the article text, only larger, colour versions of photographs used in the articles. Balsam Post is issued to members 4 times a year, and is in an A5 printed form, some 48 pages per issue.

I do have some back-copies of the issue containing the original article by Mr Wilkinson, and the Society can supply these, at a small cost. For overseas (ie. non UK) I may be willing to send a pdf of the article.

I am also willing to answer queries relating to this technique, as, like Mr Wilkinson, I feel that every microscopist should have it at their disposal. Personally, I have set it up on Zeiss (West), Reichert, CTS 2000, AO Series 10 and Nikon Optiphot stands with some success.

The articles mentioned above in Balsam Post are;

Strange's Variable Amplitude Contrast, Balsam Post 91.12, Brian Wilkinson (2011)

VAC Applications in Pond Life Microscopy, Balsam Post 100.22, B Wilkinson & J Wright (2013)

VAC 2 for Beginners, Balsam Post 102.34, Mick Chaplin (2014)

Lastly, to avoid folk thinking they are immediately going to get the effect that Spike Walker has in his shot of sponge spicules show below....he is a using a bi-polar filter.
I would suggest getting to grips with 'standard' VAC first.

Mike


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PostPosted: Thu Jul 19, 2018 2:33 pm 
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Hello Mike,

Thanks for the links and info on VAC.. looks interesting and another project to tinker with..

The Best,
BillT


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PostPosted: Thu Jul 19, 2018 6:47 pm 
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photomicro wrote:
I see that IanW has given a reference to a short discussion elsewhere on the forum.

The original articles by Strange are;

1. Strange, A., New Developments in Variable Asymmetrical Contrast Microscopy. MICROSCOPE 1989 (37) p355-376.
2. Strange, A., Variable Asymmetrical Contrast Microscopy. MICROSCOPE 1987 (35) p279-290.

Unfortunately, whilst I have photocopies of these, I do not find them all that useful, as they give very little practical detail of how to do this with your stand, if at all.

Mr B Wilkinson, in the UK took up this technique, and demonstrated it at meetings in the UK over a period of years, and it was well received. I persuaded him in 2011 to write up his methods, with full practical details, which appeared in the April issue of 'Balsam Post' the journal of the Postal Microscopical Society. This ten page article showed how to adapt the technique to a number of stands, namely using a Zeiss standard Abbe on an LCE, and phase 'turret' type condensers on Zeiss West and Reichert stands. Advice is given on cutting the discs, their size for named objectives, where to put them, and how to tweak the effect. There was also a follow-up article by Mr Wilkinson, and another by Mr Chaplin showing how he fitted his Biolam (Russian LOMO) stand for this.

Unfortunately, the PMS website (https://postalmicroscopicalsociety.github.io/index.html) does not include the article text, only larger, colour versions of photographs used in the articles. Balsam Post is issued to members 4 times a year, and is in an A5 printed form, some 48 pages per issue.

I do have some back-copies of the issue containing the original article by Mr Wilkinson, and the Society can supply these, at a small cost. For overseas (ie. non UK) I may be willing to send a pdf of the article.

I am also willing to answer queries relating to this technique, as, like Mr Wilkinson, I feel that every microscopist should have it at their disposal. Personally, I have set it up on Zeiss (West), Reichert, CTS 2000, AO Series 10 and Nikon Optiphot stands with some success.

The articles mentioned above in Balsam Post are;

Strange's Variable Amplitude Contrast, Balsam Post 91.12, Brian Wilkinson (2011)

VAC Applications in Pond Life Microscopy, Balsam Post 100.22, B Wilkinson & J Wright (2013)

VAC 2 for Beginners, Balsam Post 102.34, Mick Chaplin (2014)

Lastly, to avoid folk thinking they are immediately going to get the effect that Spike Walker has in his shot of sponge spicules show below....he is a using a bi-polar filter.
I would suggest getting to grips with 'standard' VAC first.

Mike


Mike,

In your experience, will VAC allow an 100x NA 1.25 oil achromat to resolve professionally mounted Frustulia diatom to dots? Thank you.


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PostPosted: Thu Jul 19, 2018 8:14 pm 
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zzffnn wrote:

Mike,

In your experience, will VAC allow an 100x NA 1.25 oil achromat to resolve professionally mounted Frustulia diatom to dots? Thank you.



I am afraid I have not tried it personally with higher powers than 40. However, in his article, Mr Wilkinson states;

"Fitted VAC stop 25mm. With centre 16mm. For Zeiss X100 Oil. Imm. na.1.3 (NB. The Apl. 1.4 condenser is used immersed for this 1.3 oil immersion objecive).
The Apl 1.4 W.G. Zeiss phase condenser that I have modified and reported on above will give excellent VAC with the immersion Zeiss Neofluor X 100 1.30 objective, when the condenser is itself oil immersed. Diatomists would find it impressive compared to the best bright field image possible without VAC. Only Nomarski D.I.C. surpasses (but not greatly so) and comes at a price. If oil immersion power is needed then this or a similar 1.4 oil immersion capability phase condenser should be chosen. "

I have no reason to doubt him on this, but rarely if ever use OI full stop. My own experience with diatoms (I collect, clean and make my own slides) is not in resolving the dots, though I do know that I can easily resolve Pleurosigma angulatum with several of my lenses, but that this is much easier using something to increase contrast. I am lucky in having some coated specimens, and Al-coated Pleurosigma is much easier then.

Klaus Kemp includes Frustulia rhomboides on his test plate, and am I right in thinking that the resolving power needed is similar to that required for Amphipleura pellucida?

Sorry I cannot be more affirmative for you.

Mike


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PostPosted: Fri Jul 20, 2018 6:46 pm 
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thanks for the added info.

Even with the diagrams shown on the old forum I'm still at a bit of a loss as to how it works, I guess I need to see an example implemented. I see how I *think* it might work, then suffer a brain fart once the gears start turning. I'm not as quick on the uptake as I was 40 years ago. :roll:


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