Are there low-power oil immersion objectives?

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patta
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Are there low-power oil immersion objectives?

#1 Post by patta » Sat Jun 26, 2021 6:16 pm

As from question- are there?
Like a 20x or 40x oil?

When I use the 100x oil, that's good, but often wish to go back at lower magnification. Cannot! Only the 4x is usable, looking through the oil drop.

Apart from some 70 or 60x, I've found only Lomo 30x, with weird size.
Not sure if it makes sense- but I'd really love to have, like, a 30x 0.60 oil. Maybe cleaner than the always mushy 40x?
Last edited by patta on Sat Jun 26, 2021 6:33 pm, edited 1 time in total.

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Re: Are there low-power oil immersion objectives?

#2 Post by BramHuntingNematodes » Sat Jun 26, 2021 6:26 pm

yes there are, and sometimes with large NA's given the magnification. I have a 40x 1.00NA Bausch and Lomb oil immersion Fluorite lens which is very useful when doing immersion work.
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Re: Are there low-power oil immersion objectives?

#3 Post by MicroBob » Sat Jun 26, 2021 7:59 pm

Hi Patta,
yes there are, just not as common. I have 22, 40, 50 oil objectives and like to use them with the strong 100. The medium power ones for a wider field of view, the 22 for seeking.

Bob

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Re: Are there low-power oil immersion objectives?

#4 Post by patta » Sun Jun 27, 2021 7:37 am

Nice to know! I'll look for them.

I have a 60x 1.0 Oil with iris which I find very useful; closing the iris gives a bit more depth of field, some clarity in thick subjects. Even closed at NA 0.65, it regularly looks better than the (modest, vintage) 40x 0.65 dry, who's fighting with wrong coverslips and thick mounts. But the field of the 60x isn't much larger than the 100x.

40x 1.0 sounds overkill! I was hoping for smaller NA, so to get easy focus, decent working distance.
Going backwards, "Quest for small NA"!

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Re: Are there low-power oil immersion objectives?

#5 Post by Wes » Sun Jun 27, 2021 7:58 am

There is a multi-immersion 16/0,5 plan-neofluar from Zeiss.

Image

One reason why you might want a lower power immersion objective is for fluorescence.
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Re: Are there low-power oil immersion objectives?

#6 Post by MichaelG. » Sun Jun 27, 2021 10:55 am

This, from the Leitz Heine Condenser leaflet, seems an excellent solution.
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Unfortunately; although I have the special cap, the objective itself was missing from my Heine set.

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Re: Are there low-power oil immersion objectives?

#7 Post by apochronaut » Sun Jun 27, 2021 2:08 pm

The Balplan objectives are 1/5 the magnification of their face value. The 50X planfluorite is in fact a 10X .80 oil immersion objective as are the rest, 15X 1.20 oil planapochromat , 20X 1.25 planachro and 25X 1.40 planapochromat. Lomo made a very nice 30X .90 water immersion apo.

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Re: Are there low-power oil immersion objectives?

#8 Post by apochronaut » Sun Jun 27, 2021 2:13 pm

patta wrote:
Sun Jun 27, 2021 7:37 am
Nice to know! I'll look for them.

I have a 60x 1.0 Oil with iris which I find very useful; closing the iris gives a bit more depth of field, some clarity in thick subjects. Even closed at NA 0.65, it regularly looks better than the (modest, vintage) 40x 0.65 dry, who's fighting with wrong coverslips and thick mounts. But the field of the 60x isn't much larger than the 100x.

40x 1.0 sounds overkill! I was hoping for smaller NA, so to get easy focus, decent working distance.
Going backwards, "Quest for small NA"!
Due to the immersion characteristic you aren't going to get much working distance relief with any oil objective. They all have to be pretty close to the coverslip in order to stay within the drop, irregardless of magnification. The purpose of oil is to assist in raising the N.A., so they are not lowl

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Re: Are there low-power oil immersion objectives?

#9 Post by patta » Mon Jun 28, 2021 4:03 pm

I'll try to copy Leitz and go for the homemade "immersion cap" for a dry objective then.
Use a small round coverslip as "porthole"; as near as possible to the focus plane. Maybe works.

The Zeiss Neofluars look amazing, but probably they are, so they are also expensive (the owners keep them for themselves!)

Balplan, wait. Water immersion, sure; but no more microscopes budget this month.
Working distance - we'll see!

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Re: Are there low-power oil immersion objectives?

#10 Post by patta » Wed Jun 30, 2021 4:35 am

Thank you all for the replies! I will buy all the objectives you have listed - when I'll get rich. High NA is good, oh yes. Good objectives are expensive, oh no.

Meanwhile, here is the crude temporary makeshift, an "oil cap" as suggested by MichaelG, made from a plastic cap, drilled, with a piece of coverslip sealed as porthole. It works just as "oil droplet flattener" or "objective oil protector".
Not sure if it is really useful - with the 10x 0.25 objective, the image quality is more or less the same either with the cap, or without, looking directly through the oil droplet. With the 40x 0.65, it barely works (zero working distance) and the image looks worse than with the objective dry, on dry slide. Cap not usable with the 40x.
Anyway, most important, the oil didn't get in, dry objectives clean; thanks, silicon.

Maybe the oil cap fits also on the 4x objective? Let's try. Yes it fits; let's dip it into a cup of oil. Aha! Low NA and long working distance... The working distance got even longer in oil, but image looks ok. Finally, I can observe olives in their natural environment! True oil immersion, wonder if there are some microbes that thrive here...
The cup with oil obviously fell afterwards, spilling the gallon of oil on the stage, condenser and floor. But the objective remained sealed and clean.
The cup with oil obviously fell afterwards, spilling the gallon of oil on the stage, condenser and floor. But the objective remained sealed and clean.
Oil cap with LWD oily mess.jpg (81.23 KiB) Viewed 6309 times

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Re: Are there low-power oil immersion objectives?

#11 Post by MichaelG. » Wed Jun 30, 2021 7:58 am

Nice experiment, patta

I think the [missing from my set] Leitz 10x may be specifically designed for use with its immersion cap, but I’m not sure.

… but I will have a look at the cap anyway, to see if it is plane or lenticular … I’ve never checked.

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Re: Are there low-power oil immersion objectives?

#12 Post by MichaelG. » Wed Jun 30, 2021 3:00 pm

UPDATE :

The engraving on the adapter reads J.A. Pv 10:1

It comprises two elements [possibly more ?]
The outer surface of each element is [so far as I can tell] flat

It appears to have no overall magnifying/minifying effect

This is certainly more than a coverslip, but I have yet to find any ‘formula’ for it.

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Re: Are there low-power oil immersion objectives?

#13 Post by viktor j nilsson » Wed Jun 30, 2021 3:17 pm

Could it be a set of telan lenses creating a miniature infinity space?

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Re: Are there low-power oil immersion objectives?

#14 Post by MichaelG. » Wed Jun 30, 2021 3:27 pm

viktor j nilsson wrote:
Wed Jun 30, 2021 3:17 pm
Could it be a set of telan lenses creating a miniature infinity space?
Interesting possibility, Viktor

I’m on garden-weeding duty for the next few hours; but will have a look under the stereomicroscope this evening, to see if there are more than four surfaces visible. … I don’t really want to dismantle it, in case it is something particularly clever !

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Re: Are there low-power oil immersion objectives?

#15 Post by apochronaut » Wed Jun 30, 2021 3:42 pm

There is no optical advantage to an oil immersion cap. It is simply a device to allow the continued use of low power objectives once one has committed to oiling the slide. The N.A. stays the same. This is particularly useful for DF.
The increase in w.d. is caused by the fact that 1.52 mm of oil = 1mm of air.

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Re: Are there low-power oil immersion objectives?

#16 Post by MichaelG. » Wed Jun 30, 2021 10:41 pm

MichaelG. wrote:
Wed Jun 30, 2021 3:27 pm
… will have a look under the stereomicroscope this evening, to see if there are more than four surfaces visible. …
Quick look suggests that there are only two air-spaced elements
Still guessing, but, I think the front one is plano-convex and the rear one concave-plano.

Perhaps something roughly like this:
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But I haven’t modelled the oil

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Re: Are there low-power oil immersion objectives?

#17 Post by patta » Thu Jul 01, 2021 5:01 am

That is interesting, pretty sophisticate design for the Leitz cap. I was expecting just a flat window & that's it.
I agree, the cap isn't of any advantage - apart from keeping the dry objective clean. Maybe the extra working distance allowed by the refraction index could be of some use. EPI illumination in immersion?
A related side dream is a "Water immersion macro cap", to take macro underwater. Not for the NA advantage, but to take photos of live fishes etc. Taking a macro through the glass of an aquarium results in pretty bad aberrations of sort, so it needs some correcting lenses like in previous post.
Examples of immersion macro caps (at the bottom)
https://www.uwphotographyguide.com/unde ... cro-lenses
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Re: Are there low-power oil immersion objectives?

#18 Post by MichaelG. » Thu Jul 01, 2021 6:04 am

patta wrote:
Thu Jul 01, 2021 5:01 am
That is interesting, pretty sophisticate design for the Leitz cap. I was expecting just a flat window & that's it.
I agree, the cap isn't of any advantage - apart from keeping the dry objective clean. Maybe the extra working distance allowed by the refraction index could be of some use. EPI illumination in immersion?
Not quite ^^^
The idea of the Leitz cap is to reduce the working distance of a 10x lens, so that it can work in the same drop of oil as the high power oil-immersion objectives. … Which is, I think, what you were originally seeking.

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Re: Are there low-power oil immersion objectives?

#19 Post by Rossf » Thu Jul 01, 2021 9:47 am

I can confirm that MichealG-I have that cap for the 10x Pv-it seems to only fit in the Pv 10 with the rounder front profile-I’ve got a couple of water dipping WE Pv objectives and the 10x can be used as a water dipper with that immersion cap-it’s a recommended “set” in the heine manual if wanting to get a dipping set for the heine. I thought it improved image a bit-the long barrel Leitz water immersion are really ace! 25x .75 and 50x .1-I was getting really fascinating bright field of flagellates with the 50x without phase-fanging to try it with that VAC polariser filter…
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Re: Are there low-power oil immersion objectives?

#20 Post by patta » Thu Jul 01, 2021 10:26 am

Ok so, I think I've digested a bit my initial confusion; so:

Oil immersion, I'll keep it only to push the highest NA and resolution. Requires very thin specimens, under permanent mount. The view with the 100x is not satisfactory? That's because the specimen is too thick. Wipe the slide clean and use the 10x instead; or make a better slide. Objectives with very small magnification, low NA, oil immersion, are not really useful, unless I need to observe frying chips (it may happen).

For other uses - temporary water mount of thick specimens, live critters etc (which represent 95% of my observations), water immersion is The Way, since it allows to focus deep in the specimen. Medium magnification, medium NA make sense then.

Still curious about immersion caps.

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Re: Are there low-power oil immersion objectives?

#21 Post by apochronaut » Thu Jul 01, 2021 12:15 pm

You have to be careful with water immersion. It comes in two flavours. Cover slip corrected and dipping. Cover slip corrected is of little practical advantage over oil, except for dealing with the oil, which bothers some people. Dipping objectives are only really practical in low magnifications, since the interaction of the objective and the object creates so much motion. High magnification versions are in vogue fairly recently for medical applications with confocal microscopy where the immersion medium is serum or tissue and the interaction can be controlled and stabilized. If you opt for cover slip corrected water immersion it is hard to find coherent sets. They exist at the elite end but very few companies issued a nice practical series in the past. I can't see the practicality of a water immersion cap??

The thing about immersion is that the bother of it is highest when you are using mixed mediums, that's why oil immersion caps are nice: to unify the medium. However, once you have dialed in a high magnification objective it is unlikely that you are going to want to use a 4 or 10X for actual observation ; more likely just for scanning, so the oil puddle that is left from the 50 to 100X objective is not really an impediment for scanning. Most low power objectives are not impacted by it much at all. Normally just around the edges.

Objectives in a nosepiece need to be considered in sets suited for the application. Parfocality is important but also the immersion medium and w.d. It doesn't make much sense for instance to have a high N.A. 10X objective in a nosepiece along with a 50X and 100X oil immersion used with an oil DF condenser. A standard or l.w.d. objective with a lower N.A. is much more practical. The high N.A. objective will have a close focus and be virtually unusable once oil is applied. Ditto a 20X but both in a longer working distance version with possibly even lower N.A. will be little affected by an oil puddle and still have a practical use.

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Re: Are there low-power oil immersion objectives?

#22 Post by Chris Dee » Thu Jul 01, 2021 4:10 pm

The oil immersion objectives below are Vickers 50x 0.95 NA, one is Fluoro, the other PlanAPO. Both are excellent objectives. They crop up on eBay occasionally and tend have a lower asking price that Zeiss/Nikon etc. I can assure you its not because they are inferior, sellers are often not familiar with the quality of Vickers optics from this era, worth searching for.
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Re: Are there low-power oil immersion objectives?

#23 Post by patta » Wed Jul 07, 2021 2:23 pm

Reading another thread, came out an useful application for long working distance, immersion objectives: Minerals!
A piece of mineral is immersed in a cup of oil, matching the refractive index of the crystal, so one can look inside the crystal, without need of preparation or polishing. This trick is often done to check for defects in gemstones.
Here would be good an objective made for looking through several mm of oil and crystal. Haven't found one yet. Maybe they just use low power, non-immersion objectives from some safe distance.

Vickers - thanks for the tip! I've looked now at them, the stand are painted with horrible choices of brown and beige. That may explain the low price! The "Patholette" stand is cool.

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Re: Are there low-power oil immersion objectives?

#24 Post by patta » Wed Jul 21, 2021 8:48 pm

Vickers will have to wait a little more...
got instead two "for parts" Lomo Water immersion, 30x 0.90 and 85x 1.0

The 30x is really what I was looking for, works well in temporary water mounts of pond critters; can "dive" and focus through 1mm or so of water. Very practical. I'll try if work decently also with oil.
The 85x is still in degreasing therapy, let's see

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Re: Are there low-power oil immersion objectives?

#25 Post by Scarodactyl » Thu Jul 22, 2021 4:21 am

I wouldn't put a water immersion objective in oil. Waterproof and oilproof aren't always the same thing.

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Re: Are there low-power oil immersion objectives?

#26 Post by apochronaut » Thu Jul 22, 2021 6:23 pm

patta wrote:
Wed Jul 21, 2021 8:48 pm
Vickers will have to wait a little more...
got instead two "for parts" Lomo Water immersion, 30x 0.90 and 85x 1.0

The 30x is really what I was looking for, works well in temporary water mounts of pond critters; can "dive" and focus through 1mm or so of water. Very practical. I'll try if work decently also with oil.
The 85x is still in degreasing therapy, let's see
That is the fluorite one? 32mm parfocal. I wouldn't stick it in oil. Oil creeps, has less surface tension. It's .90 in water so really good for a 30X. I can't imagine improvement in oil. Sometimes oil immersion objectives with high N.A. can work o.k. with water: acceptable but clearly at a lower N.A. and resolution but I have never seen it the other way around without changing the cover slip thickness and tweaking a correction collar.
That objective works really nicely in an AO series 4, which is built for 34mm parfocal objectives.

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Re: Are there low-power oil immersion objectives?

#27 Post by patta » Thu Jul 22, 2021 10:57 pm

Ok ok I'll keep it far from any further grease.
It took some hours to get it clean, as full of ancient Russian gummy whale oil, better not waste more time.
the whale smudge has been removed by.... WD40! Then thoroughly washed away.

Reason for dipping it in oil, was the original purpose, go to lower magnification once the slide has been covered with oil from a 100x. I had actually another top secret reason for low magnification oil, will tell later (usual pointless thinkering with lenses).
Now let's play with water for a while. Seems worthwhile.

The 30x I've got, 33-34mm, has an iris and written only "Л" that supposedly stands for Luminescence /fluorescence. . It is suspiciously sharp even at NA 0.90, so must have some good glass in it, maybe fluorite, maybe others. Although, definitely not "plan".

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