Sub-stage condenser and relay lens help, please.

[twebster]

Hi ya' guys

While I am refurbishing my Zeiss GFL I put the new objectives on my old Nikon stand to try them out. The 2 lenses I've been using the most are the Zeiss 16x Ph2 Neofluar and the Zeiss 40x Neofluar. When used for observation the image is terrific. When used for photography they're terrible...



...and, as you can tell by the inset. there is a huge amount of chromatic aberrations. This was shot on film using a Zeiss Jena 5x projection eyepiece. I checked the objective very closely and noticed a very small amount of delamination (Zeiss is known for this) around the outside of the lens elements but it is a very small amount with plenty of room between the delamination and the phase ring.

Just in case it was caused by the delamination I shot some images with the Zeiss 40x Neofluar objective...



...and got exactly the same thing, huge chromatic aberrations. The 40x Neofluar is mint with no delamination at all. I used the same 5x Zeiss Jena projection eyepiece. With a less complex subject the results were a little better but not much...



(I know, I broke my own 2-image limit per post rule.) There is still an appreciable amount of chromatic aberrations, especially along contrasty image boundaries. I shot tests with a 5x Olympus and 5x Nikon projection eyepiece and got very similar results. At least, nothing much worse than this. (BTW, I barely stopped down the diaphragm in the sub-stage condenser. Stopping it down only made matters worse.)

My question to anybody "out there" that may use Zeiss Neofluar objectives is this...Does the type of sub-stage condenser used make a big difference in the quality of images shot with the Neofluars? The sub-stage condenser on my Nikon is an Abbe NA 1.3 condenser. Is this condenser too under-corrected? I thought objectives with flourite elements were supposed to be corrected for at least 3 wavelengths of light and 2 wavelengths in spherical aberrations. The Zeiss stand came with an aplanat NA 1.3 condenser. Will this condenser give me visibly better images? Will it cut down on the aberrations?

What about projection eyepieces? I was going to try the 12.5x Zeiss eyepieces that came with the 'scope but they are badly delaminated and the image magnification is much too great for my purposes. What lens should I use? Will I have to try and find a corrected Zeiss 5x eyepiece and will it help any? I'm a bit frustrated and have put the LOMO objectives back on the microscope. Any help would be greatly appreciated.

"Thanks" and best regards to all as always,

[Ken Ramos]

I am really not sure how to explain this Tom. When I first got my Axiostar, I thought the same thing as you, that my optics were not color corrected. Well actually they are. Probably what you are seeing is the same as I see through my Axiostar. I started out with CP Achromats. I also saw what I though were chromatic abberations. Adjusting the light intensity will reduce some but not all of what you are seeing and what I believe you are seeing is not CA but a different kind of refraction of light. I know absolutly nothing about the physics of light I can only speculate on what you are seeing. Have you tried looking at a prepared slide and photographing it? The optics are so refined that, when I got my Axiostar, I was not used to seeing what I was seeing and thought something was terribly wrong with my scope. Come to find out it is working the way it was designed to. Zeiss objectives are not condenser friendly so to speak. They do have specific condensers for specific sets of objectives. But I would venture a guess that no matter which you happen to use, the result will be the same. Looking at the photos you posted, I see what you mean but however they look fine to me. Try adjusting the light intensity and centering the condenser is all I can recommend.
Edit
Oh by the way. I forgot in the confusion of trying to explain something I know absolutly nothing about. Try using a white balance filter and a white or blue diffusion filter below the condenser. That is how I reduced a good deal of the color.

[Steve West]

Tom,

I do not know that extent that the Zeiss objective design is dependent on eyepiece or photorelay correction. You say they look fine with the eyepiece, but not with the camera. Your relay may not be compensatiing like your eyepiece?? Just a thought.

Steve

[Kenv]

Hi Tom, FWIW my two cents worth. I can't help you on the hardware side of this problem but if all else fails you can use software. I sometimes get unwanted CA and I remove the colour pretty well using the Hue and Saturation tool in Photoshop, its better than nothing. I was going to post a before and after shot to show you the difference but the Image Hosting isn't working.

[twebster]

Thanks for the responses, guys

KenR...I didn't think of centering the condenser. That makes sense and may make a difference. The Nikon stand doesn't have condenser centering adjustments, though. I'll have to wait until I get the Zeiss stand ready. I don't think these low res images show the true issue. In the full res images you can see what appears to be 3 separate images in 3 colors just slightly off-register. The images kind of look like those 3D images made of green and red and you wear the funky glasses to view. I dunno they just don't look right to me.

(Oops. Forgot to add...I use an Wratten 82 series filter to correct the color of the illumination for film. With the lamp at full power I use an 82A filter. With the lamp at 3/4 intensity I use an 82B. At 1/2 power (the lowest practical setting) I use an 82C because the light is much, much redder.)

Steve...The projection lenses I used are all supposed to be corrected, at least they have the "K" marking. I know there is a difference between brands but I've used these projection lenses fairly successfully with the LOMO objectives. Could achromats be less sensitive to eyepieces than the more highly-corrected flourites? I'll try shooting another roll tonight using the Nikon eyepieces.

KenV...I've used the "Hue/Saturation" adjustments in Photoshop before but it is a pain, isn't it? Maybe I'm expecting too much from the optics. I'll have to get on refurbishing the Zeiss stand a little quicker. I don't know why the image hosting didn't work. I tried it this morning and it is OK. Whenever something doesn't work send me the error message so I can track it down. OK?

Thanks, my friends.

[twebster]

Hi ya' Steve

I just tried setting up an eyepiece to use as a projection lens. I don't think that is going to work. I have to rack the camera back above the trinocular tube nearly 16" to make the camera parfocal with the viewing eyepieces. With a real projection lens the camera back only has to be about 6" above the projection lens in the trinoc tube. I guess I could use the Nikon eyepiece and then refocus through the camera each time I want to make an image but that would get to be a hassle, I think.

Best regards,

[Ken Ramos]

Tom, though you may not be able to center the condenser, try putting in place a diffusion filter either a blue one or a white one in your filter tray. If you do not have a diffusion filter you can do this. If you have an extra clear blue filter or maybe even a yellow one, blue will be much better, try rubbing it across a piece of 80 grit sand paper and then on to a much finer grit until you get an even frosting on the glass. I have done this and it works great for the interm until you can acquire a regular diffusion filter. A round piece of clear plastic cut off of a CD case or an old cassette tape case will work also and will be much easier to frost with the sandpaper. It will just be painstaking cutting out the hard plastic. One more idea, if you donot have a filter tray or donot want to go to trouble of cutting out a circular disk from the plastic. Just use a square piece of sanded plastic placed over the top of the illuminator. This should even out your light and take some of the harshness out of the image and reduce a good amount of the refraction of light that you are seeing.

[piotr]

I missed this thread... sounds like fun!

From my experience - the corrected condenser improves quality a bit. I'm using a condenser advertised as achromatic/aplanatic, AO model 1201. Chromatic aberrations are much smaller (although not entirely gone), using regular achromat objectives. It's best visible on a border of a field diaphragm.

Despite the chromatic aberrations, your images look pretty sharp!

Anyway, I have found a useful book on Gordon's science-info website: How to Improve Photography Through the Microscope. Maybe you don't know this one. The book is by Olympus and it details photo-eyepieces and condensers related issues. Good luck, Tom!

[rene]

Hi Tom, joined your club, think there are very usefull discussions here!

Anyway, I also think this is mainly a condenser centring issue, as the chr abb is yellow on top throughout the picture. Were it eyepiece related, then it would be zero in the center, and yellow towards the edge (ie radiating from the center!).

I do not know enough of standarization of chr abb, I know that Zeiss West standarized the objectives for this with all mags, whereas it used to be depending on magnification. So the Zeiss Jena projection eyepiece might not be ideal, but likely ok if you stay away from the edge (and you do that anyway, don't you?)

I very much doubt condenser choice can ever make so much of a difference as can be seen in your images (certainly with lower mag). But i have been wrong before...

Rene.

[twebster]

Hi ya' Rene

Welcome aboard, my friend. I am looking forward to your participation. I believe you are right about my problem. I spent some time carefully aligning the condenser with the objectives and have most the chromatic aberrations, when they occur, radiating from the center of the image.

I also was using an Optovar that came with this microscope. The Optovar definitely has some issues and contributed to the problem, I think. When the Optovar was in place, the images were all shifted to the right. If I used the Bertrand lens to align the phase objectives, the image through the Bertrand lens was shifted 25% to the right. So, there must be some sort of alignment issue with the Optovar. Images made without the Optovar are much, much better. Per Ron Neumeyer's suggestion, I have mailed the Optovar to Bill Sheridan to see if it can be fixed.

Thanks for your reply, Rene. Again, I am pleased to have you and your expertise as a member of our forums.

[Planapo]

Hi all, my first post! and it's not even original but just a reply to someone else's.

160mm Neofluars are good contrasty well colour-corrected objectives, and should give no chroma at the field edges. It looks like a simple eyepiece/relay problem.

The Zeiss 160 apos and semi-apos are the most undercompensated objectives in the business and absolutely need the use of Zeiss Kpl eyepieces (Wild will do at a pinch but not Leitz or Jena), and if you are using a digicam, a Kpl eyepiece as relay. This will usually be a modified Kpl 10x/18. For a digicam a photo relay is inappropriate.

In the phase contrast image, condenser aberrations are insignificant (so most dedicated phase condensers are just Abbe) and unless the condenser is really badly aligned on the optic axis (which will be obvious) the use of a Kpl should fix this.

You will never, of course, be able to do anything about the Neofluars' field curvature, but you should get a crisp contrasty non-coloured image.

[Charles Krebs]

Greetings Planapo... welcome aboard!

a couple questions for you...

How does the correction in the Olympus NFK photo-eyepiece compare to the Zeiss Kpl for the Neofluars? I have two Neofluars that I would like use, but all I have are Olympus NFK and Nikon CF photo-eyepieces.

In the phase contrast image, condenser aberrations are insignificant (so most dedicated phase condensers are just Abbe)

This is the case with my Nikon Phase Contrast condenser. The PC objectives look great in phase, but seem pretty mediocre in brightfield. I was wondering if it was the "simple" Abbe condenser. There are quite a few times I would like photograph a subject in both phase and brightfield, but the brightfield images on the phase microscope never look anywhere near as nice as the microscope I have set up just for brightfield. I followed a recent thread over on Yahoo, and many seemed to conclude that PC objectives used in brightfield were fine, but a little lower in contrast. What's your opinion of phase contrast lenses used for brightfield?

[Guest]

What camera do you use, film or digital?

The Oly NFKs are compensating to a far lesser degree than the Zeiss Kpls. They will give rise to chromatic difference of magnification manifesting itself as coloured fringes around the edge (radial)... not exactly chromatic aberration though similar.

The Nikon CF is totally uncompensating, and is for use with the Nikon CF and (later) CFN objectives, in which all corrections are done inside the objective. Death for Zeiss objectives though.

Yes indeed, a dedicated Abbe phase condenser will give pretty poor illumination in BF, the simple Abbe is fine up to about NA=0.5 or so but more than that and the image can really suffer. That's why some makers offered a better condenser for phase, that's to allow nice BF images too. Example in point is the Zeiss VZ condenser which is 1.4NA aplanatic-achromatic, the highest possible correction, and while this is wasted in the phase images, it shows big-time when you do BF or DIC with the same condenser.

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.

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....

BTW I love your pics.

[Planapo]

The last post was from me, forgot to log in

[Charles Krebs]

Planapo...
Thanks for the reply.

Yes indeed, a dedicated Abbe phase condenser will give pretty poor illumination in BF, the simple Abbe is fine up to about NA=0.5 or so but more than that and the image can really suffer. That's why some makers offered a better condenser for phase, that's to allow nice BF images too.

That pretty much correlates to what I have seen in the images. I'm using a Canon 10D digital SLR. You can see how I'm set up here:
http://www.photomacrography1.net/forum/ ... php?t=1228

I do have an old Zeiss Kpl 63mm photo-eyepiece. I should give that a try with the Neofluars.

The Nikon CF photo-eyepieces get used with the Nikon CFN phase contrast objectives only. (I realize they are not compensating, but out of curiosity I did try them with the Olympus objectives and the results were actually quite good)

For the Olympus brightfield objectives I use the NFK photo-eyepieces, usually the 2.5X or 3.3X. I guess based on the sensor size (15x22mm) I should probably be using a 1.67X photo-eyepiece, but I'm using pretty high na objectives (S Plan Apo's) so I don't think the magnifications I'm recording on the sensor are out of line.... ie 250X 0r 330X with the 100/1.40 or 132X with the 40/0.95... (But I haven't yet been able to snag a 1.67X NFK for comparisons). So much to learn.....

Charlie