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Zeiss West DIC with Mismatched Objectives
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Cactusdave



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

PostPosted: Tue Jul 26, 2016 7:13 am    Post subject: Reply with quote

X20. The first objective option I tried at this magnification fortuitously worked well. This is the Lomo X20, 0.65 Apochromat, a short non-DIN length lens. It is another high quality 'unsung' Apochromat that can be bought quite cheaply, but undoubtedly there are bad examples around, so the usual warnings apply. To get DIC with this lens I found the best results with the X40 slider used in the orthodox upright orientation, condenser prism position II and the NA 1.4 top lens in place. The quality of the DIC was good, with almost complete extinction possible, and reasonably even DIC across the field. There was some noticeable, but not catastrophic chromatic aberration and the images were a little soft, requiring stronger Levels adjustment.

The first two images show diatoms from the same arrangement by Steve Beats that I have used previously. The first image has had the background homogenised, the second is more representative. The resolving power of this little lens is very good.








The next image shows a 17 image stack using Helicon method B of the tip of the moth proboscis. The background has had Gaussian blurring applied.



The fourth image shows the resolution of cross striations (I and A bands) in voluntary muscle of the cat tongue .



The final image shows the insertion point of muscle blocks in the cat tongue with associated capillary blood supply. These last two images are from vintage Victorian-era slide mounts.




Again very usable DIC overall and I hope a chance to show what this 'cheap' Lomo Apochromat can do. Smile
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Beatsy



Joined: 05 Jul 2013
Posts: 1540
Location: Malvern, UK

PostPosted: Tue Jul 26, 2016 9:02 am    Post subject: Reply with quote

Wow - those actin/myosin bands on the muscle shots are really rendered very nicely. Neat stuff.

It occured to me that the one thing I (we?) can't do with the prisms is tilt them away from orthogonal to the illumination axis. At least not without potentially catastrophic surgery on the mounts in my case. I wonder if that would be a useful variable to explore...

You first Smile
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Eddie



Joined: 18 Oct 2012
Posts: 141

PostPosted: Tue Jul 26, 2016 11:14 am    Post subject: Reply with quote

There is a document which shows 10 different Zeiss DIC slides are available for 11 Zeiss objectives, for use with the two DIC prisms in their newer 'S' 'T' DIC condenser.


With all these options, there maybe a prism for a wide variety of objectives. Just a matter of trial and error.

BTW: There is no DIC III prism in that model of condenser. That position is usually empty unless someone put something in there.
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 933

PostPosted: Tue Jul 26, 2016 1:46 pm    Post subject: Reply with quote

Cactusdave wrote:
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.


Hi Dave,

Thanks for the info. The new DIC condenser 465285 has 3 positions for exchangeable prisms (I, II, III), so it's not clear which prisms you have exactly (it can be any of the 4 different ones). Normally, only 2 positions are occupied but sometimes a third prism was added for use with front lens NA 0.63. The part numbers are written on the bottom rim of the prism so they are easily visible from below when you take the condenser off the microscope.

Kind regards, Ichty
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Cactusdave



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

PostPosted: Tue Jul 26, 2016 2:24 pm    Post subject: Reply with quote

Thanks for that information Ichty. I'll make a point of checking which actual prisms are present when I next get the condenser out. There is definitely a prism of some description in position III in my condenser. Buying additional dedicated objective prism sliders is very expensive, which is why I embarked on this mix and match exercise. So far it is proving your point Eddie, the two sliders I have will work reasonably well with a surprising range of objectives when all the possible permutations are tried.
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zzffnn



Joined: 22 May 2014
Posts: 1823
Location: Boston, Massachusetts, USA

PostPosted: Tue Jul 26, 2016 3:59 pm    Post subject: Reply with quote

Dave,
Please keep up the great work. I enjoy this thread and am sure it would be helpful to others as well!
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Ichthyophthirius



Joined: 07 Mar 2013
Posts: 933

PostPosted: Wed Jul 27, 2016 1:57 am    Post subject: Reply with quote

Hi Dave,

One more thing to look out for. Zeiss 160 mm objectives have an exceptionally short RMS thread+overhang. The DIC adapter rings are designed to take those short threads. Other manufacturers like Leitz (160 mm) and, I think, also Nikon, have longer threads that don't fit completely into the adapters. They push against the inside of the adapters and shave off the black antirefective paint (which in turn can drop into the inside of the objective). It can also result in high-magnification objectives to being parcentric any more. In those cases, a 1 mm spacer ring can be useful. Just something to keep in mind.

Regards, Ichty
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Cactusdave



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

PostPosted: Wed Jul 27, 2016 7:15 am    Post subject: Reply with quote

Thanks for that tip Ichty, I would never have guessed that the lenghth of the RMS thread might be an issue with non-Zeiss West objectives. I have a number of RMS spacers, but I don't think I have anything as small as 1mm. I think these thin RMS 'shims' have been sold as parfocality adjusters in the past.

I have checked the prisms in my condenser. Prism I is marked 434404 <= 16, and the II prism is marked434405 <=40. This is as expected. There is a prism in the III position. It is unmarked and looks different. It has four indentations to screw it in/out with a suitable tool and there are marks of a varnish like glue suggesting it is locked in place. Presumably this is some kind of 'special' prism which was added at some point.

It's slightly off my original topic, but I have seen prisms like this before. I have another Zeiss DIC/Inko condenser shown here http://www.photomacrography.net/forum/viewtopic.php?p=71728#71728 marked 4717120. I've never used this condenser because one of the centration adjuster, the little wheel, doesn't work. It rotates but doesn't move the phase ring which is installed, and I have my other DIC/phase condenser which works perfectly. The 4717120 condenser appears to have prisms in positions I and II. Neither are marked with any designation, and both have four indentations around the edge and appear to have glue locking them in place.
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Ichthyophthirius



Joined: 07 Mar 2013
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PostPosted: Wed Jul 27, 2016 7:47 am    Post subject: Reply with quote

Hi Dave,

OK, thanks for looking. Someone must have added the third prism from another condenser, maybe another Zeiss, but this is unlikely to have been delivered like this from the factory.

Your second condenser 4717120 (this is a serial number, not a part number; part number is likely "46 52 79" if it has 3 prism positions, I, II and III), is a condenser for the "old DIC" system. Prism III seems to be missing (these condensers always had either 3 or 4 prisms installed). They are not labelled and are glued in place to prevent disalignment.

It is quite common for the centering mechanism not to work. Either the little metal ball of the click-stop is missing (that is rare; in that case, the turret won't click into the positions either) or the turret is simply ceased up. It would have to be cleaned and lumbricated, something I haven't managed to do by myself so far.

Regards, Ichty
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Eddie



Joined: 18 Oct 2012
Posts: 141

PostPosted: Wed Jul 27, 2016 9:24 am    Post subject: Reply with quote

The prisms in the old style DIC condenser are screwed in. You can see it when you take the whole 1.4-3.2 lens housing off.

Ichy is right. The 'Wheel' operates from a ballbearing on a spring post which moves up and down a groove in the condenser. It also helps click each position in place. Most likely cause is the lubricant has hardened and prevents proper movement. It is easily fixed by removing both top and bottom cover. Lift all the items out, (be careful of the wheel with the prisms and phase annuli)...the outside ring, the center post is in two pieces, one rotating in the other with one attached to the arm operating the lateral adjustment. Clean the old lube off everything that has old lube on it. The ballbearing is loose and just sits on top of a spring on the center of the 'Wheel' mechanism . Clean that and the spring post as well, and put a dab of grease on top of the spring to hold the ball in place as you put everything back together again.
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Cactusdave



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

PostPosted: Thu Jul 28, 2016 1:28 pm    Post subject: Reply with quote

Thanks for that useful information Eddie. I have printed it for future use. I've never seen any kind of diagram of the inner workings of one of these condensers.

X16. Returning to objectives that work with my sliders, I decided to revisit X16 after all. Although the Zeiss West X16, 0.35 Planachromat works well and is a very decent lens, I remembered that I had got very good DIC with my Nikon Diaphot DIC setup using a Reichert X16 fluorite objective, and thought it was worth giving this a try. This objective is marked Reichert Fluor (X)16 0.50 160/0.17. With the high NA of 0.50 for a X16 it has very good resolving power and is a very nice lens in normal brightfield use. It is a short non-DIN length objective. It gives very good DIC with my Zeiss Standard setup using the X16 objective slider in the normal orientation and with the condenser in the I position. The 1.4 NA condenser top lens is in place. These are the same conditions as for the Zeiss X16 Planachromat. Very nice DIC can be obtained, approaching full extinction.

The first illustration shows the same Beats diatom arrangement with the usual minimal processing. The central dark shadow can be reduced by lowering the condenser, but at the cost of lessening the DIC quality. The image is made from 9 images stacked with Helicon Method B.




The second image is from the Victorian slide of a cross section of cat tongue injected to show capillaries. It shows a detail of the insertion of some small muscle blocks which run more or less vertically in the plane of the section. They run between other muscle blocks which run transversely through the plane of the section. Details of the voluntary muscle cross striations can be seen nicely. This is stacked from 29 images using Helicon Method B. The capillary supply for the different muscles is beautifully shown.




All in all this lens is a good alternative to the Zeiss X16 planachromat at this magnification.
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Cactusdave



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

PostPosted: Fri Jul 29, 2016 1:37 pm    Post subject: Reply with quote

A couple more images from the Victorian cat tongue section with the Reichert Fluor X16, 0.50. It really does give good DIC. These images show how the unstained nuclei of cells in the thinner parts of the tongue papillae are resolved. The thin adhesive film, (albumen, gelatine?) used to attach the section to the slide is also clearly visible.



Stack of 23 images, Helicon Method B



Stack of 26 images, Helicon Method B
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Eddie



Joined: 18 Oct 2012
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PostPosted: Fri Jul 29, 2016 3:54 pm    Post subject: Reply with quote

Those look incredible.
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Cactusdave



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

PostPosted: Sun Jul 31, 2016 3:35 am    Post subject: Reply with quote

Thanks Eddie. I appreciate that.

Next we go on to X25 as we move onwards and upwards in magnification. I had intended to stop at X40, but I may see If I can go beyond at all. Anyway, at X25 there is a very nice objective option and it's maybe not to hard to guess what it is ...............
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Cactusdave



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

PostPosted: Sun Jul 31, 2016 4:49 am    Post subject: Reply with quote

X25. I was very pleased to find that the Zeiss West X25, 0.65 Planapochromat gives very good DIC. I had high hopes for this lens as it gives reasonably good DIC with the X40 prism on my Nikon Diaphot. The conditions are X40 objective prism the right way up, and the II condenser position.

This X25 lens is a very fine one in any use, the only criticisms I would have is that this, like many Zeiss West 160mm lenses, is often found to be delaminated to a greater or lesser extent. Serious delamination across the whole aperture of the objective can really spoil the image to an unacceptable extent, but peripheral delamination, which can still seriously damage an objective's retail value, may have much less impact. Reduction in image contrast leading to a soft, or in bad cases, almost fuzzy image is the usual symptom. Minor reduction in image contrast can be recovered in post processing so my advice is don't always overlook that prized objective that the honest seller has admitted to be delaminated. As long as you can return it if you are not happy, it may be worth a trial. My other criticism, or warning is about the very small working distance. I can't find this quoted anywhere, but for a lens of relatively modest magnification and NA it's tiny. There is a real danger of crashing coverslips, and some vintage mounts with thicker coverslips are unusable with this objective.

Anyway here I some images. The quality of the DIC is pretty good and it is possible to get a range of DIC colour from almost full extinction through shades of grey. I remember being told that the best DIC is when the background is 'silver grey' whatever that is. It is certainly true that the best DIC effects are usually with a mid grey background rather than close to full extinction. Compare these two diatom images, one near full extinction one nearer mid grey. Both are from an arrangement by Steve Beats and are single unstacked frames.

Near full extinction




Mid grey





Voluntary muscle in a Victorian section of cat tongue. Single unstacked image. The cross banding shows up very nicely.





Another diatom from a strew from Oamaru, New Zealand, Cormack's Sidings by Meakin. Stack of 20 images with Zerene DMap.




Finally a bit of fun. Another diatom from the thick Cormack's strew which contains diatoms in interesting 'postures' a stack of 43 images with Zerene DMap and some PMax retouching plus quite a lot of post processing and still far from perfect, but certainly an unusual view.


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