Sub-stage condenser and relay lens help, please.

[Planapo]

I think the "old" Zeiss 63mm Kpl should help your edge image a lot. Gut feeling.

As far as I know, all Zeiss Oberkochen projectives are old, as the Zeiss camera systems of the 70s onwards (MC63, MC100 etc) had internal relay optics, and used a normal eyepiece (usually 10x) as the projective, whether a 35mm camera or plate was connected. So if what I think is right, there aren't any newer e.g. 2.5x Kpl projectives around.

But if you have SPlan Apos, why use Neofluars?

IMO the only Neofluars which really cut the candy are the three multi-immersions, for their fine contrast, near-apo correction, enormous NAs and fully plano field (unfortunately, they do all have one sometimes-troublesome drawback too). But that's another matter. When I photo with these using my Nikon Coolpix I use a threaded Zeiss Kpl 10x eyepiece as relay.

[renevanwezel]

What camera do you use, film or digital?

As for phase objectives used in BF, it's an old old question with some people insisting the BF image is degraded by the phase ring, others saying it isn't... for myself I happily use phase objectives in BF and DIC, though I have otherwise identical non-phase objectives too, and would offer a prize to anyone who could consistently tell me which BF image came from a phase obj and which came from a similar non-phase obj.

Dear guest (can we have your name please?)

I agree, there are strong feelings on this issue. I never was concerned with the small differences between images, I'm just not good in those comparisons. However, a camera does pick up these differences in contrast pretty well, and when I was forced to put these images side by side (in order to know what I was talking about) I was astounded by the differences. If you make identical pictures (and make sure you put auto sharpness/contrast OFF), I'm pretty sure the differences are clear to everyone. I've used Wild phase fluotars and non-phase fluotars by the way.

The ring size also has effect on the image, older phase objectives have larger rings for max resolution in PC, and then they behave even worse, but my own experience is limited to old Vickers objectives in this matter.

Naturally, the objective quality plays a part, and a phase image is less critical in some ways than BF so an objective that gives an acceptable phase image may not be good in BF. But as regards comparing the BF images made by similar-specification phase and non-phase objectives, there's no noticeable difference...Just another urban myth I think, of which there are lots in circulation....

Not too sure on this matter either, I've come across statements that phase objectives are more critical for spherical abberation, and therefore better corrected. I doubt the latter is the case with modern objectives, but I can see the point of better correction needed for phase images, as there is less direct light, and therefore the edge of the objective (where sph abb is worst) becomes more important in image formation. But that is just intuition from my part.


Rene.

[Planapo]

Dear Rene... the quoted bits were from me, I posted immediately afterwards to identify myself as the "guest" culprit.

I have to admit to the world that I have never... shame on me... taken sets of comparison photos using phase and non-phase objectives. It would seem to be a clincher of this argument one way or the other. I shall do so and report my results, maybe even post a couple of pairs.

My everyday objectives are Nikon CFN planapos, which are the only ones I have in both phase and non-phase. These have a smallish diameter phase ring; however it is the thickest (i.e. broadest) phase ring I have ever seen so maybe this would exaggerate the effect. We shall have to wait and see.

But, visually, neither I nor anyone invited to try have been able to distinguish.

The ring size also has effect on the image, older phase objectives have larger rings for max resolution in PC, and then they behave even worse, but my own experience is limited to old Vickers objectives in this matter.

I have not met many people who recognise that the diameter of the phase ring affects resolution (which brings up a good question... why do modern manufacturers compromise the res of phase images by making the rings so small?). I tried the visual experiment with Leitz Heines, which have a huge ring, with similar results though... not able to see differences. But I got rid of these objectives so can't do the photo experiment.

I can see the point of better correction needed for phase images, as there is less direct light, and therefore the edge of the objective (where sph abb is worst) becomes more important in image formation.

I don't think there are any rules here. For a given, let's say middle-quality objective, with the outside of the optical system being less good than the centre, the image quality will be proportional in some way to the diffractivity of the object. With highly diffracting objects the final image is very largely formed from rays which have passed through the periphery. With non-diffracting objects the image is formed from direct rays of which the bulk will not be passing through the periphery.

So yes, there is some sound basis to what you wrote there, if we assume that the kind of images that people will view in phase contrast are those of very diffractive objects.

But I don't think there was ever a phase objective, apart perhaps from the Heines, which was specially designed for the work. Mostly they were and are just BF objectives with a phase ring at the appropriate place.

Despite this I have not seen any objective which performs significantly "better" in phase than BF or vice versa. Objectives I have used have been anything from superb to total crap but have usually shown their quality in all techniques. (The exception would be an objective which has strains so can't do good pol or DIC work).

Anyway there is now a question in my mind so as soon as I have the time I'll do the comparison shots and convince myself once and for all one way or the other.

Peter

[Guest]

Dear Rene... the quoted bits were from me, I posted immediately afterwards to identify myself as the "guest" culprit.

Hi Peter, yes, I saw your planapo-ID afterwards, but still didn't get your name. Sorry, have probably missed out on it in earlier posts.

I have not met many people who recognise that the diameter of the phase ring affects resolution (which brings up a good question... why do modern manufacturers compromise the res of phase images by making the rings so small?). I tried the visual experiment with Leitz Heines, which have a huge ring, with similar results though... not able to see differences.

The Vickers were poor in contrast; I assume therefore that larger ringsize results in poor(er) contrast, akin to closing condenser iris in BF results in more contrast.
Never had the opportunity to work with the Heine, I do believe however that the rings are very small compared to most?? This would minimize contrast loss.

Here are two images from a test slide with a 40/0.75 Wild Fluotar, BF and phase. This time in BF, no processing whatsoever, cropped from the 'fine' Coolpix990jpg, max optical zoom. Eyepiece: Leitz 10xperiplan. Condenser: Wild achro/aplan with central stop. I've used an interference green filter, which I wouldn't advice to use, as a blue/green or blue filter would give far better resolution.



Similar pictures with a blue/green filter can be found on the yahoo microscope photo section, http://photos.groups.yahoo.com/group/mi ... =gr&.view=
I'd like to do these again with a blue filter some time (as they don't print right) but the gain in resolution is enormous, as you can see. Likewise comparisons in BF show similar reductions in contrast, as Frez showed about a year ago. I was critical at the time, but had to admit it after tests...


Rene.

[piotr]

Rene, may I ask you a question (a little bit off-topic). Is the Wild Fluotar objective (like this 40x/0.75) compatible with Zeiss Kpl eyepieces?

[Guest]

This post was (too)quickly written, some more about it:

The Vickers were poor in contrast; I assume therefore that larger ringsize results in poor(er) contrast, akin to closing condenser iris in BF results in more contrast.

I mean: the image in phasecontrast shows less contrast with larger phase ring!

Never had the opportunity to work with the Heine, I do believe however that the rings are very small compared to most?? This would minimize contrast loss.

Less contrast loss in BF with a thinner phase ring (smaller area).

I'd like to do these again with a blue filter some time (as they don't print right)

With the blue/green filter, I can't get good prints as they come up far too intense in green compared to the visual. BTW, I'm amazed the bluegreen filter gives such good results compared to the green interference filter. I've also tried a lomo achro water immersion 40/0.75 with the green filter, but image was inferior to the fluotars, even the phase fluotar was doing better. That was another results I didn't expect, as an achro should perform almost similar to an apo in green light! Apparently not. Exp not finished yet...



Rene.

[Guest]

Rene, may I ask you a question (a little bit off-topic). Is the Wild Fluotar objective (like this 40x/0.75) compatible with Zeiss Kpl eyepieces?

Hi Piotr, can't say for sure, but don't see a reason why not. I have 12.5x periplansGF, 10xperiplans for the coolpix, 10x JenaPK, 15x Wild W comp, and they all do fine in the center of field. (I have no plan objectives anyway, so some chromatic abb is no problem as it will only show in the perifery). I'm not fickly with eyepieces anyway, have used noncompensating 15x eyepieces from a cheap stereo for years, just because they had such a nice widefield. With plankton that's far more important then abberations...

Rene.

[Mike]

Hello Planapo,

We actually went through this about a year or so ago on the 'other' forum (Yahoo!) as a consequence of one of my posts.

I did a 'side-by-side' comparison with identical (other than one being phase and the other not) objectives. There was a noticeable difference, ("softer" "Less crisp") with the phase vs. the BF with shots taken moments apart on the same subject/same lighting.

This was confirmed by a number of respected microscopists, so I must take exception to your categorization as 'urban legend'. Your not seeing it doesn't mean it isn't so.

If you wish to research the discussion, it may be found starting with post #12611 December 2003. (Be forewarned - it goes on for quite a bit!)

One of the most telling responses was from Bob Brewer in which he recounted an experiment (#12652) done at a Zeiss dealership with blind multiple photos taken with known slides and BF and Phase objectives used side-by-side. The consensus was the Phase objectives gave a 'softer' image than the BF, albeit not dramatic, but nonetheless discernible. This was confirmed by other notables in the microscopy world.

The infamous Frez also did side-by-side comparisons with identical (other than BF vs. PC) and came up with the same conclusions, posting the images for all to see and note.

All the best,

Mike

[piotr]

Thank you very much, Rene. Yes, the chromatic aberrations were my concern.

Interesting - the difference between BF and PC objectives is very pronounced in your pictures. These are dark ground illumination images. Can you see any difference in regular brightfield pictures, too?

[Charles Krebs]

Planapo...

But if you have SPlan Apos, why use Neofluars?

I had the Neofluars before I could find/afford the S Plan Apo Oly's. And there's no way my progeny will will be allowed to crush coverslips with the Plan Apo's. I would like to set up a scope with the Neofluars so I don't have to break out in a sweat when someone else wants to cruise a wet mount.

To add to the current conversation... I really like oblique brightfield illumination. My Nikon CFN Plan phase objectives just do not do well at all with oblique brightfield (but again, the phase images look great). The resolution is good, but there are all sorts of color artifacts that don't really look like chromatic aberrations or CDM. I too have not done enough testing to see where the problem is, but I'm leery of using phase objectives wirth oblique light.

[Guest]

Thank you very much, Rene. Yes, the chromatic aberrations were my concern.

Interesting - the difference between BF and PC objectives is very pronounced in your pictures. These are dark ground illumination images. Can you see any difference in regular brightfield pictures, too?

Hi Piotr, see Keith's response. Frez did a great collage for BF, some people didn't believe it would be similar for DF, so I did that not long ago (and on the same diatom as Frez originally started on). Charles' note that COL/oblique shows artefacts calls for investigation... Who's next?

Anyway, the consensus was that the differences seem far more pronounced when comparing images then a direct visual; I did suggest at the time that a camera is less forgiving in this respect and therefore more capable to show these differences then your brain can make out with a visual through the eyepieces. Seems like a contradiction, just think about it.

Anyway, I'm off to bed, and hopefully I'm NOT going to dream about it!

R.

[Planapo]

Looks like I'm going to be busy with doing comparisons and photographing them. I take all the various points below:

Quote:
But if you have SPlan Apos, why use Neofluars?
Answer:
I had the Neofluars before I could find/afford the S Plan Apo Oly's. And there's no way my progeny will will be allowed to crush coverslips with the Plan Apo's.

Definitely understand this line of reasoning!

I really like oblique brightfield illumination. My Nikon CFN Plan phase objectives just do not do well at all with oblique brightfield (but again, the phase images look great). The resolution is good, but there are all sorts of color artifacts that don't really look like chromatic aberrations or CDM. I too have not done enough testing to see where the problem is, but I'm leery of using phase objectives wirth oblique light.

This will be fun to try. Nikon CFNs ought to give no CDM at all though the Plans will have some CA. I have some of these and will do a few tests and compare with the CFN planapos which normally show no perceptible CA.

This was confirmed by a number of respected microscopists, so I must take exception to your categorization as 'urban legend'. Your not seeing it doesn't mean it isn't so.

I do totally agree with the second bit as I may well see what someone else will miss and vice versa, of course. As for urban legend, well I will humbly swallow that remark if I can photograph differences with the equipment at my disposal.

I will be able to do these also in blue as I have a blue interference filter with cutoff at about 510nm. If the filtered photos don't come out well printed why not convert the file to B/W?

I've also tried a lomo achro water immersion 40/0.75 with the green filter, but image was inferior to the fluotars, even the phase fluotar was doing better. That was another results I didn't expect, as an achro should perform almost similar to an apo in green light!

Apples and oranges. Lomo is, well, Lomo. I used to have a 10x/0.30 Lomo marked "planapo" that was not particularly plan and very far from apo. I also had the Lomo 40x/0.75WI once but disposed of it... Lomo is great because cheap and cheerful (and available) but I wouldn't bank on their performance. Wild on the other hand is up there with the best, better IMO than Zeiss.

Never had the opportunity to work with the Heine, I do believe however that the rings are very small compared to most?? This would minimize contrast loss.

The rings are narrow and much greater in diameter than most. I really couldn't say how this affects the image apart from giving better res in PC. The images are super but have a big field curvature. I flogged the objectives but kept the condenser which is great for all sorts of trickery.

Here is a final thought. Many PC condensers are plain-Jane Abbe as that's really all that's needed for PC. But using such a condenser in BF will certainly not help the image. Some PC condensers are apl-ach and these would give a fairer comparison, I think, as we would then be normalising the substage illum to be as good as it could be for all techniques.

This is enough theorising, and I will be off to do some comparison snaps in due course.

Peter

[Mike]

Hello Planapo,

No 'urban legend swallowing' allowed on this forum!

I should have been clearer as regards the difference between the lenses - it is very subtle, and almost assuredly would not be noticeable by normal observation. My search was to obtain the sharpest shots possible with photomicrography, and being somewhat anal, I typically become obsessed with the details.

I am using Leitz Orthoplans now, and am fortunate to have complete sets of Plan apos and quality Phacos in thier own nosepieces. Switching nosepieces literally takes seconds, and the Zernicke condenser has not only the phase annuli, but DF and BF as well. As a consequence, it is normal for me to lee the phase nosepiece in the stand and switch back and forth between phase and BF when doing visual observations.

It will be interesting to see the results of your testing, but having said that, it is always necessary to issue the disclaimer - YMMV!

All the best,

Mike

[Guest]

and being somewhat anal, I typically become obsessed with the details.

Yeah, I guess we're often looking too much at the image instead of the specimen, if you get my meaning.

Concerning the Lomo quality, the Lomo medium power waterimmersion is able to give some remarkable results, like perfect imaging at the bottom of a cavity slide (like with a hanging drop). You try that with the average dry 40x... Peter might regret in some time parting with such a lens, who knows.

But yes, in ideal conditions, the lomo lens doesn't do very well compared to the Wild fluotars. I was hoping that because of the water immersion, contrast would increase enough to play equal with the 'big boys'. Apparently not.

Rene.

[Guest]

Oh yes, the lomo 40xWI is a Zeiss design from around 1890. That deserves some respect, whatever it's worth.