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Zeiss West DIC with Mismatched Objectives
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Cactusdave



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PostPosted: Tue Jul 19, 2016 8:35 am    Post subject: Zeiss West DIC with Mismatched Objectives Reply with quote

I have a Zeiss West DIC system, this is the latest Zeiss 160mm Zeiss DIC system which uses individual sliders for each objective. I have two sliders, one nominally for the X16 Zeiss Planachromat, and one nominally for the X40 Planachromat. I also have a Zeiss DIC condenser with prisms I, II and III, phase rings Ph1 and Ph2 and brightfield. I was interested in the discussion in this thread http://www.photomacrography.net/forum/viewtopic.php?p=191773#191773 . The thread discusses the possibility that objectives other than the ones actually recommended by Zeiss might give usable DIC with the Zeiss prism sliders. My experience with the Zeiss 40X, 0.95 planapochromat http://www.photomacrography.net/forum/viewtopic.php?p=183205#183205 and with the very different DIC system on my Nikon Diaphot suggested that indeed there is a degree of tolerance and that unexpected objectives can give good DIC. For example the Lomo 20X, 0.65 apochromat gives excellent DIC with the Nikon 40X condenser DIC prism http://www.photomacrography.net/forum/viewtopic.php?p=160515#160515 . I was therefore particularly interested in this link http://www.microscopeitaly.it/2009/11/30/zeiss-nomarski-d-i-c-160mm-terza-e-ultima-versione/ . Although this is from an Italian microscopy site, much is translated into English, highlighted in yellow further down the page and in any case it is presented in an easily understandable form. It gives some very useful suggestions of potential pairings of objectives and sliders for the Zeiss DIC system, including some quite unexpected combinations, and with the added twist that some objectives give good DIC with the slider inserted upside down!

One deficiency in my DIC setups is the absence of a low power DIC option. In all my trials with the Nikon Diaphot DIC, I haven’t found a reliable combination of objective and condenser prism for less magnification than offered by a X10 objective. Since the Italian link reported successful pairings at X6.3 and even X4, I was keen to start at this end of the magnification range. I have now looked at these magnifications pretty thoroughly with the objectives I own, and have expanded further to find good DIC options at X10, X20 and X25.

Before going through the results in detail, it is worth making some general comments. The Zeiss DIC sliders are flimsy, delicate and very expensive second hand. If you are inspired to experiment please be careful when handling these sliders, as you may be swapping them round a lot. Don’t over tighten or loosen the knurled knob on the end of the DIC slider, which is one of the adjusters you’ll be using frequently. Be very careful not to touch the prism surfaces with fingers when handling them.
You will need to optimise every factor under your control when trying to get good DIC. This includes the orientation of the slider, the knurled knob on the slider itself, the two controls on the condenser, the same ones you use to centre the phase rings, the height of the condenser, the centring of the condenser, and the setting of the condenser diaphragm aperture. For objectives X6.3 or lower the NA 1.4 aplanatic/achromatic top lens may need to be unscrewed from the condenser to allow full field illumination.
Some of the objectives I recommend are non-DIN length so-called short, or RMS objectives. These do not need to have a DIN extender fitted to reach focus. The mount for the DIC slider acts as an extender, and should allow these short objectives to reach focus. However be aware that parfocality with other objectives in the nosepiece will be completely lost, so take great care when moving between objectives to avoid crashes.

There are a couple of other things to think about when doing this kind of mix and match approach. It is possible to be fooled by some rather DIC-like oblique effects which can be present when there is just a strong dark band of contrast across the field in the back lens, viewed without an eyepiece, rather than reasonably even DIC. See this thread http://www.photomacrography.net/forum/viewtopic.php?p=25941#25941 and other posts on ‘VOILA’ illumination.

Another thing to be aware of is that as mismatched objectives are being used, almost by definition there is going to be chromatic aberration, which isn’t too serious at low power, but can be a problem at higher powers. Also do not expect the really even grey backgrounds that can be achieved with perfectly matched objectives and sliders. This needs to be accepted and dealt with in post processing if problematic. Yet another factor is differences in the quality of DIC obtained between individual slides and coverslips. I work a lot with vintage Victorian prepared mounts and I have found that these sometimes give much better DIC than modern mounts, either permanent, or temporary pond sample mounts. I always use a modern diatom mount and some kind of living sample in my tests.

Now the results. I will illustrate these with some images, but I’ll probably post more in the ‘Photography through the Microscope’ section.

X2.5. I have not found any combinations which give workable DIC at X2.5. This is probably just a step too far.

X4. Now it starts to get more interesting. I have found three objectives that give reasonably useful DIC.

I have not been able to replicate the beautiful example of DIC of a Charchesium colony in the Italian report, using the Zeiss Planapo X4, 0.14 and the conditions described there. However I have got usable DIC with this objective. The settings that work with this objective are as described in the Italian report. X40 prism slider inverted, position II condenser prism and no top lens. The first image with this combination shows a section from a modern arrangement of diatoms by Steve Beats. This has had basic colour correction and Levels adjustment and some sharpening of the web-resized image, but the uneven background is representative.



The second image shows a crop from a stitched image of a coiled moth proboscis (tongue) a Victorian mount by C.M. Topping. The image illustrates the more even DIC with this old slide.




The second objective I got reasonable results with is the Leitz plan fluorite X4, 0.14. This is an older 170mm tube length, 'short' objective. Settings are again X40 prism slider inverted, position II condenser prism, and no top lens. The image shows the same Beats diatom arrangement.



The background is representative. This lens gives a better DIC image than the Zeiss Planapo with this test subject at least. I have not tested it further.


The third X4 lens that gives usable DIC is the more modern Leitz 160mm tube length Planapo X4, 0.14. The settings are once more X40 prism slider inverted, position II condenser prism and no top lens. The image shows the same diatom arrangement again.



This lens again gives nice DIC with a more even background than the Zeiss. It also works well with an old Victorian mount of a cat tongue injected to show capillary network, another of my favourite test mounts. This image is cropped from a 23 image stitch made with Microsoft ICE.





To be continued.
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Cactusdave



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PostPosted: Wed Jul 20, 2016 7:47 am    Post subject: Reply with quote

X6.3. I have found several objectives that give good results, but two are outstanding and give DIC images that are as good as I would expect from a dedicated objective and slider pair. The objective I have used most and tested with the greatest variety of subjects is the Zeiss Jena X6.3, 0.20 Apochromat. This is a DIN length standard 160mm objective and the example I have performs extremely well in both DIC and brightfield applications. It is one of those ‘unsung’ Apochromats from Zeiss Jena and Lomo that can be picked up without breaking the bank.

The settings that work best with this objective in my hands are X16 objective prism inserted upside down, and the DIC condenser prism in the I position. These are different from the settings suggested in the Italian report. In my hands the X40 slider used reversed as in that report does not work with this or any other X6.3 objective I have tried.

The first illustrative image uses my Steve Beats modern diatom mount.



This image has just has colour correction. Levels adjustment and light sharpening.

The second image made with this objective shows a section of cat tongue with a large filiform papilla used by the cat in rasping food and grooming. The image is a crop from a larger stitch of 43 images. The background has been homogenised in this image.




The third image using this objective is a crop from a stitched image of the moth proboscis. The background has been evened using Gaussian blurring. I think this image gives a good impression of the optical quality of this objective and what good DIC it gives.




The second X6.3 I have got really good DIC with is the Zeiss West Neofluar X6.3, 0.20. This objective works with the same settings as the Zeiss Jena lens, X16 objective prism inserted upside down, and the DIC condenser prism in the I position. I have not tried this lens as extensively as the Jena X6.3, but it may be as good as that lens for DIC.

First image is the Beats diatom arrangement. Again only colour correction, Levels and light sharpening.



The second image shows the filiform papilla from the cat tongue again, this time cropped from a smaller 14 image stitch. the background has not been modified.



X10 next!
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Charles Krebs



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PostPosted: Wed Jul 20, 2016 3:15 pm    Post subject: Reply with quote

Very interesting. From these examples the 6.3X DIC looks excellent... better than I get at 10X with the Olympus or Nikon Diaphot.
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Cactusdave



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PostPosted: Thu Jul 21, 2016 7:38 am    Post subject: Reply with quote

You raise an interesting question there Charles. How to compare DIC quality on different manufacturers' stands? I only have only personal experience of the Nikon Diaphot with the DIC LWD 0.52 NA condenser and the last 160mm iteration of Zeiss DIC on a Zeiss Standard 18 with a Zeiss DIC condenser with the NA 1.4 aplanatic/achromatic strain free top lens that can be unscrewed to reveal a NA 0.32 lens underneath. When I'm comparing like with like, i.e. DIC with objective NA less than or approximately equal to condenser NA, then yes the Zeiss DIC when everything is perfectly optimised is probably better than the Diaphot DIC. I'd have to make some qualification of that. My experience of X10 DIC on the Diaphot with the Nikon Plan X10, 0.25 DIC objective and my condenser has been that it is excellent. While I have had good DIC on the Diaphot with other X10 objectives, X20 objectives and X40 objectives, nothing quite matches the Nikon Plan X10, 0.25 DIC for uniform background and DIC depth. I would also say that I've seen some beautiful DIC images at X10 with the Olympus BHS that more than matched in image quality anything that I can get on either my Zeiss or Diaphot. http://www.photomacrography.net/forum/viewtopic.php?p=128891#128891 for example Wink Very Happy
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zzffnn



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PostPosted: Thu Jul 21, 2016 8:32 am    Post subject: Reply with quote

Interesting thread. How do images look when you go over NA 0.5?

I remember an Italian microscopist (in his web site) showed that even at higher NA, mismatch DIC can still work reasonably well.

I am guessing at around NA 0.25, one may not see a big difference (at such low NA, many simple DIY illumination can perform quite close to DIC anyway)?
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Cactusdave



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PostPosted: Thu Jul 21, 2016 1:35 pm    Post subject: Reply with quote

Zzffn, the Italian microscopist you refer to is the one linked in my first post in this thread. It is true that DIC-like effects can be obtained on a budget with a variety of techniques especially variations on oblique lighting such as the universal gradient filter you have experimented with yourself, circular oblique illumination, http://www.microscopy-uk.org.uk/mag/artjan03/pjcol2.html and amplitude contrast techniques like VAC-2 http://www.microbehunter.com/forum/specimens-samples-and-slides/arthur-stranges-variable-amplitude-contrast-method-vac-2/ . However proper DIC when it works well gives better results, more predictable, less prone to artefacts and with a more even background. It can also be used at higher magnification and higher numerical aperture, where some other methods fail. Yes, mismatch objective DIC does work with higher magnification, and higher NA objectives, but I haven't explored this in any detail with objectives above NA 0.65 yet.
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Pau
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PostPosted: Thu Jul 21, 2016 1:41 pm    Post subject: Reply with quote

Nice to get DIC at so low magnification! I whish to have it.

lf you have the 0.63 lens cap for this condensers it's also worth a try: with my older system it provides the best DIC for 25X, both with Planapo and NPL Fluotar
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zzffnn



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PostPosted: Thu Jul 21, 2016 2:57 pm    Post subject: Reply with quote

Thank you very much, Dave.

Sorry, I missed that part of your first thread. Indeed, that Italian microscopist mentioned that his (3rd gen) Zeiss DIC system works well with short LOMO 40x NA 0.95 apo. But not so well with LOMO 60x oil apo, for example.

I have no doubt that DIC, perhaps even with some mismatched objectives, wins at higher NA over DIY methods (shadow-free optical sectioning ability of DIC is unique). I have tried most of those DIYs myself and prefer offset COL over UGF/GUF at NA of over 0.65.
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Cactusdave



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PostPosted: Fri Jul 22, 2016 2:13 am    Post subject: Reply with quote

Pau, I don't have the 0.63 NA lens cap, but I can probably borrow one. Your suggestion is an interesting one. At X10 and above I have been using the 1.4 NA top lens. At X6.3 I get good DIC both with and without the top lens. At X4 I need to remove the top lens to fully illuminate the field. At X10, X16, X20, and X25, I get good results with the high NA top lens on.

X10. I struggled to find an objective slider combination that gave good DIC at this magnification. I tried a good many that didn't work with either of the sliders that I have available. Failures included the Zeiss Planapo X10, 0.32; the Wild Fluotar X10, 0.45; the Lomo Achromat X10, 0.40, and the Vickers Planapo X10, 0.32 amongst others. I don't have a Zeiss X10 Planachromat which I would have liked to test. I did eventually find an objective that works very well for DIC. This is the Leitz Plan fluorite X10, 0.30 170mm. This is a 'short' non-DIN lens. It gives very good DIC with the X40 objective slider inserted the right way up and the condenser prism set to position I. I also get DIC with the condenser prism in position II, but I seems to work best. The 1.4 NA top lens is in place.

The quality of the DIC is very good and it is possible to get 'full extinction'. The first image shows close to full extinction with some diatoms from the Steve Beats arrangement.



The second image shows part of the moth proboscis including the tip. this is a single unstacked frame. Background has been modified only by Gaussian blurring. Colour correction, Levels and light sharpening has been applied.



The third image shows a single tongue papilla cropped from an image of a Victorian cat tongue section involving 83 stitched images.



The final image is an abstract of congealed excess Canada balsam at the edge of a coverslip after a rather bad bit of mounting (not mine)! This has been converted to black and white in Photoshop CS6, and is a nice illustration of the DIC 3D effect.




All in all I was very pleased with the DIC from this objective/slider combination. There are many other X10 objectives, especially Leitz it would be worth trying, but this is a very good objective in its own right and I shall continue to use it for DIC as well from now on.
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Pau
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PostPosted: Sat Jul 23, 2016 3:51 pm    Post subject: Reply with quote

Excellent 10X DIC!
The only of my 10X objectives that delivers DIC is the Pl Fluotar 10/0.30 *160 with prism 2 and no condenser cap
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Cactusdave



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PostPosted: Sun Jul 24, 2016 7:51 am    Post subject: Reply with quote

Thanks Pau. Generally I'm very impressed with the quality of the DIC I get from the Zeiss Standard DIC system I have. It's quite fiddly, I don't know if that's a word that translates well, maybe complex is better, to set up and get the very best for any given combination of objective, slider and condenser prism setting. There are a lot of things that can affect the quality of the DIC, as I mention in my first post in this thread. Seemingly small changes, for example to condenser height, can make a dramatic difference to DIC quality. The Nikon Diaphot DIC is easier to set up and more 'forgiving' in this respect.
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PostPosted: Mon Jul 25, 2016 10:25 am    Post subject: Reply with quote

Great thread Dave! Early on you mentioned centering of the condenser being important. I've only used that to align condenser diaphragm(s) with objective apertures. Does adjustment (de-centering) make appreciable differences to the subject and/or background DIC rendering for you? I had a very quick fiddle with it but not much changed - bar a very slight shift of background gradient. My Zeiss DIC only uses I and II prisms so it's possibly a later version than yours.

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Cactusdave



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PostPosted: Mon Jul 25, 2016 2:16 pm    Post subject: Reply with quote

Thanks Beatsy. My original comment on the importance of centring the condenser was really a general one. When making many different changes that can affect an image, it's not a bad discipline to try to keep the condenser centred. In practice I find that precise condenser centration doesn't have a big impact on low magnification DIC at X10 and below, when condenser height has a much bigger impact. This is as noted in the Italian author's report. At X16 and above, getting the condenser centred has definite benefits.

X16 I plan to show some results with a X20 objective next. X16 is covered nicely by the Zeiss West X16, 0.35 Planachromat which is the designated lens for the X16 objective slider. This combination gives excellent DIC, and I haven't felt the need to look for an alternative at this magnification as the image quality of the objective itself is very good.
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Ichthyophthirius



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PostPosted: Tue Jul 26, 2016 2:53 am    Post subject: Reply with quote

Hi Dave,

You found some excellent combinations; thanks for sharing this here.

I hope I didn't miss this in your text but what condenser are you using? It sounds like an "Old DIC" condenser.

There are two distinct Zeiss DIC concepts for 160 mm microscopes:

"Old DIC" http://www.mikroskopie.de/mikforum/read.php?1,18235,18235 INKO with prisms I, II, III and sometimes IIII and a common large slider in the intermediate tube

"New DIC" http://www.microscopeitaly.it/2009/11/30/zeiss-nomarski-d-i-c-160mm-terza-e-ultima-versione/ with two different condensers ("46 52 85" for NA 1.4 and "46 52 73" for NA 0.63) and the little sliders and slider holders for each objective. There are 4 different prisms that can be found in the condenser, n.A. < 0.5 434404/>0.5 434405 in condenser "46 52 85" for NA 1.4 as well as n.A. < 0.5 434406/>0.5 434407 in condenser "46 52 73" for NA 0.63 http://img4.fotos-hochladen.net/uploads/zeissdicneu1847cf9d2n.jpg but sometimes they were mixed up by previous users.

Which condenser do you use? This would be useful to know for other users. Normally, old DIC and new DIC don't mix because the distances of the interference fringes is different (their orientation might also be different, I don't remember) but if you also change the objectives, you will get some useful combinations regardless.

Changing the lens cap from NA 1.4 to 0.63 also changes the distance of the interference fringes (you can see the effect by looking through the tue with eyepieces removed) and this will give you additional combinations to try out!

Kind regards,

Ichthy
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Cactusdave



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PostPosted: Tue Jul 26, 2016 6:21 am    Post subject: Reply with quote

Icthyophthirius --- I tried to describe the Zeiss DIC system I am using in my first post, but possibly it wasn't clear. I should have given the DIC condenser part number for greater clarity. It is what you call Zeiss 'New DIC', the last DIC version that Zeiss made for 160mm finite microscopes AFAIK. This is described in some detail in the Italian report you reference, and I also quoted in my first post in the thread, and also here http://www.the-ultraphot-shop.org.uk/faq.htm about half way down the page. This version uses individual sliders for objectives, and I have the slider designed for the Zeiss X16 Planachromat and the one designed for the Zeiss X40 Planachromat.

My condenser is 465285-9901 which has the removable NA 1.4 Aplanatic/Achromatic top lens with a 0.32 NA lens under. This condenser has prisms I, II and III in place and all are functional. it also has Ph2 and Ph3 phase rings and the J brightfield position. It is mounted in what I believe is a Zeiss Standard 18 frame with trinocular head, which has a simple polariser below the condenser in the light exit, and a flip in/out analyser below the head, controlled by a rod. The polariser can be rotated but the analyser is fixed.

Unfortunately I don't own a NA 0.63 top but I'm hoping to borrow one to experiment with.
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