NIKON PlanApo 100X/140 oil that is a PlanApo 60X/140 oil

[stjepo]

I am trying to measure the NA of the lenses I have acquired and see any discrepancies that may exist with the specifications described on the barrel of these lenses with an Apertometer.

To do so I have based myself on the articles by Dushan Grujich and Craig Downing and thanks to this I have discovered that I have a NIKON PlanApo 100X/140 oil lens that is actually a PlanApo 60X/140 oil lens and that compared to another one with the same characteristics it seems slightly lower and with less clarity in the images it produces.

Is there anyone who has had the same thing happen to them?

Steve

[stjepo]

Is there a possibility that it was a fake Nikon Objective?

Steve

[stjepo]

The objectives

[stjepo]

At the end a 60X objective with the frontal lens of a 100X it must affect the performance of it.

[PeteM]

I'm not entirely clear what the problem is. The 60x Plan Apo pictured on the right has the same wider front element as the one I own. I'd have to check in storage if the 100x Plan Apo also looks right.

Have you checked the actual magnifications with a slide micrometer? Is the labelled 100x actually delivering exactly 60x?

It could be that some previous owner - with some skills or somewhat intrepid - tried swapping the front element of your 100x to restore a broken or fouled objective to sort-of usable condition - either for personal use or profit. It could also be that there is just some slight loss of alignment - a shim out of place etc. Does it look, from any telltale signs at the back, that the objective has been opened up?

If so, you might inquire from the source of this objective.

[apochronaut]

Oil invasion can coat internal lenses and alter their magnification, if it is not very bad. . This will result also in a loss of image quality : poor contrast , ca and sa.
While oil invasion usually results in devastating effects on the objective's performance, I have had the above happen on two occasions. The first totally stymied me because the objective worked but the magnification was way off and the image not great. I thought a lens element must have moved internally somehow but upon breaking the objective down, I found a thin layer of oil clinging to surfaces but still leaving the expected air spaces, so the objective worked in an altered fashion.
The second time, I knew what was going on.

[stjepo]

Thank you both PeteM and apochronaut for your responses.

PeteM, there is no sign that the lens of the 'strange' APO 100X has been opened from behind.

back 100X nikon.jpg (60 KiB) Viewed 3392 times

Apocronaut, the problem may be that oil has entered the objective, although when inspecting the lens of the 'strange' APO 100X with a binocular microscope it appears clean, transparent and crystal clear. Of course, the image it produces is not as spectacular as expected from a good APO 100X lens.

I estimated the new magnification of the 'strange' APO 100X by measuring a sample with an eyepiece calibrator. I used an Apo100X and an Apo 60X, both without any defects, and compared those measurments with the one of the "strange" Apo 100X.


What I will do now is measure all 3 using a calibration slide.

[stjepo]

As promised:

'Strange' PlanApo100X image looks little bigger but very similar to PlanApo 60X image and far from its real size.

Maybe someone at the Nikon factory mixed up the parts when the lens was being manufactured.

Can oil entering the lens cause these results?

Maybe, for me this is something new and strange.

[stjepo]

'Strange' PlanApo 100X superior lens.

[apochronaut]

As promised:

'Strange' PlanApo100X image looks little bigger but very similar to PlanApo 60X image and far from its real size.

Maybe someone at the Nikon factory mixed up the parts when the lens was being manufactured.

Can oil entering the lens cause these results?

Maybe, for me this is something new and strange.

Your low magnification planapo 100X also has a skewed image with incressing sa and ca to the left as presented. Leave the objective on it's side in the warmth overnight and see if the distribution of distortion changes. The symptoms you have can definitely be caused by oil invasion because the oil changes the curvature of the lenses and is seldom evenly disttibuted. Another possibility is a dropped out element, which moves closer to the front ; still magnifying but less. Usually though, in such a case there is worse ca. Or both. One caused by the other.

[stjepo]

Apochronaut I will 'leave the objective on it's side in the warmth overnight and see if the distribution of distortion changes'.

Excuse my ignorance but what is 'sa and ca'

Is there any solution to fix it without opening it?

A crazy idea, if your theory that oil has penetrated in the lens is confirmed, would be to soak the objective in Isopropylene for a while and thus dissolve the oil. In any case, the current condition of the objective is of little use.

Another solution would be to open it and clean it, possible problems: difficulty in disassembling it and the collimation.

Do you have any experience with NIKON lenses?

Thank you for your help.

Steve.

[stjepo]

Apochronaut you have nailed it, after the comments you have made to me and with the help of a binocular microscope I have been able to see a small bubble on the side of the lens that is fixed. I guess it's the oil that has penetrated inside.

[apochronaut]

Unfortunately, you cannot clean the objective effectively without disassembly.

[stjepo]

Is it easy? Have you done it?

Would it work to soak it in alcohol and then put it in a vacuum chamber to remove the liquid and oil?

Thanks for your help

[stjepo]

Any advice from you will help me.

Sorry and excuse my ignorance what is 'sa and ca'

Regards

Steve

[Hobbyst46]

Any advice from you will help me.

Sorry and excuse my ignorance what is 'sa and ca'

Regards

Steve

Spherical aberrations and chromatic aberrations, respectively.

[apochronaut]

ca = chromatic aberration. sa = spherical aberration.
I've done lots of objectives. It isn't that hard once you know the individual disassembly procedure of the objective and you observe certain procedural guidelines. Objectives are assembled as a centered device, so maintaining rotational alignment of the elements is critical. They used to scribe them but not so much in later years. You can scribe the cells and shims to a mark on the barrel as the stack comes out.
My memory isn't clear whether I have cleaned one of those but I think I have. I remember doing one with an iris, which is more complicated. I'm pretty sure everything comes out through the back, once the retaining ring and spring are removed on that one. The stack usually has to be driven out using a tool, especially if oil and suction are involved. The cells in the barrel are tighter than a piston.

Sometimes the oil can cause separation and or get into a sealed cell. That is a death sentence unless you can find the same objective with a different problem. Then you will have to determine the shimming, which increasingly over time is more standardized. Identical objectives have different shimming due to glass batch differences. Shimming is used mostly to refine sa to within spec.

I doubt if vacuum suction of the dissolved oil will work. You would need a lot of solvent and the risk of pulling a lower lens element out of a cell exista, if weakly assembled. I ran into one similar objective that had a very weak furl on the lower element in the second or third cell. It had dislodged just enough to distort the image. There is also the problem of the oil absorbing small amounts of compounds from inside the barrel over time, copper oxide or sulphate , paint, just carrying some contaminating dirt with it. There will be a residue left on the lenses. Some internal coatings are softer too, and subject to damage.

I use scentless dish detergent to get rid of the oil and finish with water and ipa. Clean everything individually and inspect each part under a stereo and the lenses in oblique light prior to reassembly.
A solidly made plastic tube of the correct diameter works well as a driver. Usually firm thumb pressure will do the job but sometimes a firm tap with a small mallet is needed to break the lens stack free.Once free the stack usually moves with moderate pressure. Be carefull to keep the order of all components when pushing out the stack, especially any shims. Shims sometimes look the same but when you mic. them there are small differences in thickness.

Although the oil usually enters around the front bezel, it creeps and can be way up in the lens stack. Clean everything.

Always, only apply pressure to the bezel or metal surrounding a lens, never to a lens. Assembly is the reverse of disassembly but in certain barrels, aligning the cells so they can be slid in as a stack is difficult and the components need to be put in in smaller packages, always observing the scribed alignment.

[stjepo]

I don't know how to thank you for the advice you've given me. It is a complete lens repair manual.

There is one last question: How do you seal the lens to prevent oil from entering again when it is used again?

Again, I don't know what words to use to thank you for the advice you have given, surely more people will benefit from it.

Steve

[stjepo]

Apocronaut, before daring to disassemble the lens, I put it in a small Vacuum chamber at very low pressure and managed to get small drops, possibly oil, to come out. I know it is not the solution but I had to try it and now I share this experience.

I'll see if there is any improvement or not and post the result.

[Sure Squintsalot]

I have just just completed the dissasembly of an oil soaked 20x Nikon lens. It may have been used in an inverted scope in its previous life. When I got it, the image it produced was atrocious, yet there didn't seem to be anything obviously wrong with it; complete oil saturation and no bubbles looks no different than a normal lens, in this case.

As took my lens apart, I recorded each step with photos, and proudly reassembled the unit, until I saw two shims on the carpet.

The shims are very thin and are practically invisible when viewed edge on. You may even accidentally wipe the spacer tube and permanently mangle the shim, so, be very careful and gently brush the tube edges for the presence of shims. Oil will make them stick and a solvent cleaning will loosen them to the point that a casual touch will remove them entirely. Work on a white surface.

[stjepo]

Thank you very much Sure Squintsalot, it is very valuable advice.

I must confess my fear of not being able to properly disassemble and assemble this microscope objective. My only experience was a few years ago when I acquired an old Spencer microscope, I managed to bring it back to life as it was in poor condition and came with a 100X objective through which you could see... the darkness. I opened it and as we say in Spain “sin encomendarme a Dios o al diablo” (English equivalent Imprudently, rashly), It was completely detached and it was difficult to clean the lenses and sticky interior parts. I managed to put it back together (a few times since I honestly lost the order of the pieces) until I manage to see the specimen or something similar because it was very blurry. The experience traumatized me a lot... I'm kidding

I am delaying the repair of my microscope objective with the excuse of using my vacuum system, but at the end and as Apocronauta says there is no other way to fix it than to carefully disassemble it.

As another Spanish saying says: “Total de perdidos al rio” (English equivalent could be “as well be hung for a sheep as for a lamb.”).

Steve

[stjepo]

Vacuum pump experience report:

The good news:

The big bubble has disappeared!

Now the bad news:

I have a lot of tiny bubbles very well distributed throughout the lens and the image is now completely blurry!

[Hobbyst46]

I doubt that vacuum alone will eliminate trapped oil (if it is oil). Vacuum accelerates evaporation. Perhaps the abrupt decline of air pressure, when the vacuum pump was turned on, disintegrated a large oil drop to small droplets. Admittedly, small droplets will evaporate much faster than a large drop. Gentle heating (say, to 50 celsius - not sure about the heat resistance of the objective, given different expansion coefficients of the components) during the vacuum treatment will accelerate the evaporation, but it is still expected to be very slow. Not to mention residues that remain attached to the glass.

[stjepo]

I doubt that vacuum alone will eliminate trapped oil (if it is oil). Vacuum accelerates evaporation. Perhaps the abrupt decline of air pressure, when the vacuum pump was turned on, disintegrated a large oil drop to small droplets. Admittedly, small droplets will evaporate much faster than a large drop. Gentle heating (say, to 50 celsius - not sure about the heat resistance of the objective, given different expansion coefficients of the components) during the vacuum treatment will accelerate the evaporation, but it is still expected to be very slow. Not to mention residues that remain attached to the glass.

I completely agree with you. Yes, I have managed to remove most of the small bubbles but I am afraid that it will leave residue that will make it impossible to have clean lenses for adequate vision through the objective.


I have to go to plan B, yes or yes. (Open the objective)

[stjepo]

The time has come to dare to open the NIKON lens.

Preparation like a surgeon, gloves, clean area, white background, protected lenses and the appropriate tools.

To avoid scratches when opening the barrel I have protected both the tool and the bottom of the objective.

IMG_0412.JPG (55.88 KiB) Viewed 2697 times

Without much difficulty the cylinder opens and I begin to unscrew it, it gently slides down until...
...it goes round and round but the spring does not come out no matter how many turns I give it. I try by pulling on the edge but the cylinder doesn't come out, hmmm... it's time to admit that I need help...

IMG_0413.JPG (62.1 KiB) Viewed 2697 times

Is there a safe way to separate it without using to much force? Is there a screw or some piece that I haven't discovered that needs to be removed first?

apochronaut sorry to bother you again but do you have any idea how I should open it properly?

[stjepo]

A new view of my problem

[Chas]

Do just check (with a stereo or magnifier) that above or below the knurled ring there isn't another thread that splits the barrel.
It is sometimes a bit of a guess whether an edge is just a machined ledge or the edge of a thread .. scraping into the edge with a needle can sometimes help to see what is going on.

I should say that this objective is much more modern than the objectives that I am used to

[Sure Squintsalot]

I have never taken apart that unit.....however, see if the lower barrel isn't just a cover and see if it unscrews. It may hide a very small lock screw.

[stjepo]

Thank you Chas and Sure Squintsalot for your ideas seems not to be any screw and the lower barrel doesn't move.

[Chas]

There are quite a few objectives taken apart on this site:
https://www.funsci.it/schede-tecniche.html

(It doesn't have your objective, but it might give some general idea about how it might be put together)