Affordable finite low magnification oil iris objective list

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zzffnn
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Affordable finite low magnification oil iris objective list

#1 Post by zzffnn » Thu Jan 13, 2022 11:37 pm

Dear all,

I am buying a ~$200 USD finite ~40x oil iris objective for darkfield and COL, please kindly let me know your recommendations.

I would require it:

1) be equipped iris diaphragm , with NA ranging from about 0.6 to about 0.8 (wider range is fine, though 0.6-0.8 is required);
2) be of "oel" or oil type immersion (not water / dry objective);
3) have parfocal height of 33mm or 45mm (37mm old Leitz plus Leitz Plezy lens adapter will work too; but 34mm parfocal old Nikon would not work, 36mm parfocal Olympus would not be ideal);
4) provides around 40x at 160mm tube length

I already have: two 33mm parfocal oil immersion objectives at 25x NA 0.6 (adapted LOMO 190TL achromat) and 60x NA 0.7-1.0 (LOMO apo) and one 45mm parfocal objectives at 100x NA 1.32 iris (Zeiss Jena NF apo).

From Ichthyophthirius' list at http://www.photomacrography.net/forum/v ... nification
I gethered this list:

quote
Best buy:
Zeiss Planapo 40/1.0 Oil Iris (breathtaking contrast; good working distance; iris for darkfield use)

Inexpensive alternatives:
Leitz NPL Fluotar 40/0.70
Zeiss Achromat 40/0.85 Oil (very good for visual; long working distance; not so great for photos)
Zeiss Neofluar 40/0.75

Affordable alternatives:
Leitz NPL Fluotar 50/1.00 (very high contrast, good for photos; excellent all-rounder)
Leitz Achromat 50/1.00 W water immersion (very good for visual; long working distance; not so great for photos)
Leitz PL Apo 40/0.75
Zeiss Apo 40/1.0 Oil Iris
unquote

Would you please help me remove the dry objectives and add you recommnedations, if you are certain that they are oil immersion type?

The Zeiss Planapo 40/1.0 Oil Iris is slightly too expensive for my casual use, though I will consider it, if it is right at $200 USD shipped.

Another one I would consider is Nikon (45mm) plan achromat 50x 0.85.

I know at oil immersion NA around 0.6-0.8, tube length difference of 10mm is not detrimental. So an 170mm Leitz oil objective will work, as long as it comes with Leitz Plezy adapter. I understand eyepiece compensation may be different, but can tolerate that in this case.

Anything else I should look into? Thank you very much!

I understand have 33mm and 45mm objectives together in the same 5-hole nosepiece is not convenient, though it will work in my hands. I will simple shim a 45mm parfocal dry 10x to be pilot lens for my 45mm parfocal 100x. My 33mm parfocal 25x oil objective has long working distance to be pilot lens for my LOMO 60x iris objective.

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Re: Affordable finite low magnification oil iris objective list

#2 Post by BramHuntingNematodes » Fri Jan 14, 2022 12:09 am

if you got the the $200 just get the Zeiss plan apo right? I bet if you send some offers around you'll get a bite there's one on sale right now for about that much
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Re: Affordable finite low magnification oil iris objective list

#3 Post by zzffnn » Fri Jan 14, 2022 12:16 am

Thanks, Bram. I prefer to spend less at 40x (I think lower NA ~0.8 immersion doesn't really require apo correction).

I got my 100x 1.32 iris apo for $120 USD shipped, so I am hoping to pay about the same for 40x. Getting that Zeiss planapo 40x for $200 shipped should not be difficult, I agree.

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Re: Affordable finite low magnification oil iris objective list

#4 Post by PeteM » Fri Jan 14, 2022 3:09 am

Both the Nikon and Olympus finite 50x plan oil iris objectives work well IMO - and can be had under your budget.

Wouldn't the photo corrections of whatever of your microscopes provides the best and best corrected images to a camera be a deciding factor in choosing between Leitz, Nikon, Olympus, Reichert, Zeiss etc.?

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Re: Affordable finite low magnification oil iris objective list

#5 Post by patta » Fri Jan 14, 2022 8:03 am

Can't help with the choice, just complicate the matter:
Another affordable alternative is to get a couple of objectives without iris, and equip them with funnel stop at a desired aperture. A nosepiece with many identical 40x, but different NAs! After few trials, it should become clear what aperture is working best. (maybe not for COL)

The aperture stop of the funnel won't be in the right place, but so are also the irises of most iris objectives (see Lomo 60x 1.0 -0.7). Also funnel centering, ain't worse than an iris.
Maybe a complete darkfield system from a single manufacturer have condenser and objective apertures that are conjugate, maybe, but otherwise it is unlikely that they would match exactly.
Last edited by patta on Fri Jan 14, 2022 9:15 am, edited 1 time in total.

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Re: Affordable finite low magnification oil iris objective list

#6 Post by Alexander » Fri Jan 14, 2022 8:52 am

Leitz NPL Fluotar 40/0.70: dry and no iris
Zeiss 40/0.85 Oil: no iris
Zeiss Neofluar 40/0.75: dry and no iris
Leitz Fluotar 50/1.0 oil: no iris
Leitz 50/1.0 W: water, not oil and no iris
Leitz PL Apo 40/0.75: dry and no iris

Based on your requirements of oil immersion plus iris your choice is very limited. There are a number of low magnification objectives with iris from Leitz but they are all dry and have NA's below your requirements. A proper darkfield condenser could be a solution for you. I easily produce a dark field with my Leitz PL Apo 40/1.0 oil despite the fact that it has no iris.

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Re: Affordable finite low magnification oil iris objective list

#7 Post by MicroBob » Fri Jan 14, 2022 9:26 am

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Re: Affordable finite low magnification oil iris objective list

#8 Post by Hobbyst46 » Fri Jan 14, 2022 12:04 pm

Fan, I can testify that the Zeiss 40X1.0 oil with iris gives excellent DF with either a cardiodid or the built-in DF stop in the turret condenser.
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Re: Affordable finite low magnification oil iris objective list

#9 Post by zzffnn » Fri Jan 14, 2022 4:04 pm

Thank you, gents.

I insist on getting an oil iris objective, because I think it may be useful for COL as well, in addition to darkfield.

Yes, I have been playing with cardioid, paraboloid ("proper" / dedicated darkfield) condensers and darkfield stops for 4 years now.

And yes, I am well aware that objective NA 1.0 can work in darkfield with a nicely prepared thin diatom on a permenant slide, even though NA 0.8 is a safer bet with thicker/ messier water mount.

And yes, that Zeiss 40x NA 1.0 iris apo is what I am leaning towards, though I haven't found one listed for under 200 USD.

I am also wondering for NA 1.0 COL, which condenser solution I should use:

1) a DIY patch stop centered perfectly at my turret condenser (with phase annulus replaced with a bigger DIY patch stop), even though the turret condenser does not have internal mirror surface typical of dedicated darkfield condensers;

or

2) a dry 0.7-0.9 dakrfield condenser (but I think its stop size at NA 0.7 is too small for nice contrasty NA 1.0 COL, even though it has internal mirror surface for better light efficiency).

I am leaning towards 1) here.

I am fortunate have a very powerful 30W LED, so light is enough (even for 100x objective NA 1.1 darkfield using Leitz Heine).
Last edited by zzffnn on Fri Jan 14, 2022 4:43 pm, edited 3 times in total.

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Re: Affordable finite low magnification oil iris objective list

#10 Post by zzffnn » Fri Jan 14, 2022 4:37 pm

patta wrote:
Fri Jan 14, 2022 8:03 am

Can't help with the choice, just complicate the matter:

Another affordable alternative is to get a couple of objectives without iris, and equip them with funnel stop at a desired aperture. A nosepiece with many identical 40x, but different NAs! After few trials, it should become clear what aperture is working best. (maybe not for COL)

The aperture stop of the funnel won't be in the right place, but so are also the irises of most iris objectives (see Lomo 60x 1.0 -0.7). Also funnel centering, ain't worse than an iris.

Maybe a complete darkfield system from a single manufacturer have condenser and objective apertures that are conjugate, maybe, but otherwise it is unlikely that they would match exactly.

Thank you, patta. So based on your personal experience, such mismatch at conjugate plane is common with mixed brands?

I don't mind doing some trial-and-error, however multiple funnel stops (NAs) for many 40x objectives on the same nosepiece would be too complicated for me in practice, even though it makes sense in theory.

Getting funnel stops of the right size and to the right height is not small work for me (which may require DIY matching and optical calculations), I have done it once but don't want to do it again.

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Re: Affordable finite low magnification oil iris objective list

#11 Post by MicroBob » Fri Jan 14, 2022 8:53 pm

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Re: Affordable finite low magnification oil iris objective list

#12 Post by patta » Sat Jan 15, 2022 1:20 pm

I don't have real darkfield experience; this summer on a thread about condenser aberrations, we found out that aperture planes usually don't match, unless sheer luck; that was for phase contrast, annulus and ring.

In particular, darkfield patch stop and the iris of the Lomo 60x, won't ever be in focus together. I think it is the same for all objectives with iris above the optics. Cardioids, no idea.
The position oc the stops can be observed with a "phase telescope" or much better using a macro lens and camera, looking down the tube, focusing in the middle of the objective.

But maybe the smoothness of COL comes indeed from condenser and objective stops being a bit defocused, so the light-dark transition is soft.

Funnels, if you have a 3D print, can use the models from the hugely popular "Funnels Funnels" thread, won't be too much work to print a bunch of them.

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Re: Affordable finite low magnification oil iris objective list

#13 Post by zzffnn » Sat Jan 15, 2022 5:42 pm

patta wrote:
Sat Jan 15, 2022 1:20 pm

I don't have real darkfield experience; this summer on a thread about condenser aberrations, we found out that aperture planes usually don't match, unless sheer luck; that was for phase contrast, annulus and ring.

In particular, darkfield patch stop and the iris of the Lomo 60x, won't ever be in focus together. I think it is the same for all objectives with iris above the optics.

Cardioids, no idea.

The position oc the stops can be observed with a "phase telescope" or much better using a macro lens and camera, looking down the tube, focusing in the middle of the objective.

But maybe the smoothness of COL comes indeed from condenser and objective stops being a bit defocused, so the light-dark transition is soft.

Funnels, if you have a 3D print, can use the models from the hugely popular "Funnels Funnels" thread, won't be too much work to print a bunch of them.
Thank you for replying honestly.

However, I would respectfully request that you refrain from commenting (mainly not to confuse other beginners), if you have no real experience of something. Hearsay + some optical knowledge is very different that real experience.

Phase contrast has more stringent optical alignment requirements than darkfield. I am speaking from real experience as a PhD microbiologist and an experienced hobbyist microscopist.

No, a macro lens is no better than phase telescope for alignment, mostly worse. In fact, most macro lens (if you use them in reality) are too bulky to focus down microscope tube that deep, unless you have that Laowa probe lens with LED ring light around lens thread. I am not sure, even that Laowa lens may be too wide to go into microscope eye tube (of course it depends on which microscope, 23mm vs 30mm, ect).

I can do phase alignment with my naked eyes, and my AO series 4 that comes with a removable phase telescope attachment lens (which works perfectly), which is why I did not even ask for help with phase telescope or optical alignment.

Sorry to be so blunt, but "maybe" is not what I ask for here. There are quite some "maybe" 's in your post that I do not agree with.

Good COL, in my eyes, requires a good compromise between getting great contrast + 3D relief without too much hard shadows (basically by controlling how wide the illumination ring is, wider means less hard shadow but at the cost of getting less contrast or 3D relief); I personally don't aim for "smoothness" in my COL.

Maybe you prefer smoothness in your COL, which is fine with me. I am not sure most people want smoothness in COL though.

Now let us get back to opening post's topic, please.

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Re: Affordable finite low magnification oil iris objective list

#14 Post by patta » Sun Jan 16, 2022 11:47 am

Must admit, I've got pretty outraged, but let's keep it nice, technical and not too far from oil irises.
I see now, you have a pretty impressive archive of work on darkfield; I respect that; please be patient, my current obsession is aperture axial position, and I drop it in every post!

The macro lens as phase telescope works fine (after extensive use in reality); I recommend everybody to try it! Its use is not for alignment or centering, but it is needed to see where the aperture plane lies axially; meaning, the condenser patch stop gets refocused in the "objective back focal plane": but where exactly? At the objective iris, or a little below? With the phase telescope, or naked eye, it is difficult to see because they don't have enough NA; while with the macro lens it becomes very clear what is happening.

If the darkfield patch isn't exactly in focus over the objective iris, its borders are blurry and then some light spills out; that's one main reason why we need to keep a substantial distance between the illumination center stop NA and the objective iris NA.
In my direct experience, this issue gets worse with lower magnification objectives; because of their longer focal length and larger field, they're more sensitive to small mismatches in the aperture plane axial position, resulting in heavy defocus, heavy light spillover.
This aperture plane defocus is also a main cause of darkfield or phase working differently in the center vs in the corners of the field. No maybe, thorough investigation.

Smoothness of COL, ok, that was definitely off-topic. I'm very curious about this method, but I've not found yet any account on precisely how COL works (after moderate experimentation and research). I'm here to listen any idea better than the "defocused smoothness". Please be nice with beginners, maybe they know some optics. Otherwise I'm not going to sort out in detail the mechanisms of diffraction and 3D relief formation in COL, and certainly I will refrain from explaining the results, in plain words and for free on a forum. COL has still many "maybe" and many unexplained empirical tricks, I'd like to understand them better, and hope other amateurs share this interest.

Back to oil iris, the other method I'd dare to suggest, not mentioned yet, is to install a "4F relay" over the intermediate image, with a standard photographic iris in the middle; as recently illustrated by some beginner. Centering is a total hassle with this setup, but it provides the iris control for any objective; crucially, the position of this iris can be conveniently adjusted axially, so it can be put perfectly in focus with the darkfield center stop. That is not the case for objectives with built-in iris (unless we have great freedom moving up and down the stop in the condenser). The 4F relay mentioned, can cost about 200$ in parts, and turns any 40x oil into a 40x oil iris.

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Re: Affordable finite low magnification oil iris objective list

#15 Post by zzffnn » Sun Jan 16, 2022 3:11 pm

^ Since nobody else has more actual oil iris objectives to suggest, I am happy to try that "4F relay" method and report back in plain English.

Please tell us how in plain English, step by step, how to:

"install(ing) a "4F relay" over the intermediate image, with a standard photographic iris in the middle"

in an average microscope for a hobbyist micro-photographer.

I am not outraged by you or your posts, but please understand that you were talking about things that I did not even ask for (many of which were totally off-topic) in MY thread (which was set up to request a practical product list).

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Re: Affordable finite low magnification oil iris objective list

#16 Post by Scarodactyl » Sun Jan 16, 2022 7:20 pm

No offense but boy does this not seem like a great way to motivate people to go out of their way to help you with your research.

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Re: Affordable finite low magnification oil iris objective list

#17 Post by patta » Mon Jan 17, 2022 5:53 pm

No problem, relay, I'm making the drawings, will take some time.
Meanwhile, the macro as centering telescope was described here, see post #59 and #66
viewtopic.php?f=5&t=12402&start=30
A "4f relay" is here
viewtopic.php?f=12&t=13740
Can be made also in different manners. I fear you won't be much satisfied unless we figure out how to make the aperture iris centerable with precision. Now I'm centering the stop with "a kick here, a shim there", it works but ain't speedy nor pleasant.

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Re: Affordable finite low magnification oil iris objective list

#18 Post by zzffnn » Mon Jan 17, 2022 6:26 pm

patta wrote:
Mon Jan 17, 2022 5:53 pm
No problem, relay, I'm making the drawings, will take some time.
Meanwhile, the macro as centering telescope was described here, from post #59 on
viewtopic.php?f=5&t=12402&start=30
A "4f relay" is here
viewtopic.php?f=12&t=13740
Can be made also in different manners. I fear you won't be much satisfied unless we figure out how to make the aperture iris centerable with precision. Now I'm centering the stop with "a kick here, a shim there", it works but ain't speedy nor pleasant.
I am happy to hear / see your infinity rig set-up and maybe even purchase an infinity microscope just to do that.

However, with my current finite rig:

If I understood it correctly (I did not spend much time), that finite rig in your photo does not provide iris NA control for visual darkfield.

I want to see, with my eyes, nice darkfield and COL effects. Virtual darkfield effect (produced by computer software) can be easily generated by inverting a contrasty brightfield image.

Personally, I wouldn't modify my finite rig with such a long trinocular tube. For me, microscopy is also about comfortable viewing experience. Ergonomic implementation is very important. That finite rig in your photo, I am afraid, wouldn't work for me because of this.

I suspect an infinity setup would be much more ergonomic for visual darkfield.

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Re: Affordable finite low magnification oil iris objective list

#19 Post by patta » Mon Jan 17, 2022 6:54 pm

Aha, no, right, the relay I've done only for the digital, no visual. Well, it is sure possible to put an eyepiece on the top, but will be pretty awkward. Anyway, scheme drawings coming at some point. And yes, the one in the photo has no iris, instead had a set of fixed apertures with different diameter, relatively easy to swap; ok for the task then.
Actually I didn't think that it could be useful for darkfield, that's new in this thread...
Infinity, my hope was that an external iris could be fitted without a relay, but that's still not clear. I have no infinity scope, may someday try with just one, borrowed, objective.

I've seen (on paper) old Phase contrast systems that had a proper relay as accessory below the head (AO Polanret?), that would be ideal, but no idea how to get one today.
Last edited by patta on Mon Jan 17, 2022 9:11 pm, edited 2 times in total.

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Re: Affordable finite low magnification oil iris objective list

#20 Post by apochronaut » Mon Jan 17, 2022 7:27 pm

Actually, the cheapest way to get into high resolution DF is to go the AO or Reichert infinity route, simply because those systems are undervalued, not well recognized as to potential and priced often very low. The quality is stupendous. Either the 34mm or 45mm parfocal system works extremely well. Of the 34mm system objectives the 100X planachro oil with iris has been selling in the 150.00 range and the 50X oil with iris even much less. The # 1309 .66 dry 40X performs way beyond it's N.A. class. AO called it an advanced planachro. Probably it has either fluorite or other low dispersion glass in there. Cardioid oil condensers for the 10/20 series at least are abundant and have been selling as low as 40.00. They are adaptable to a series 4 as well, where certain apochromats could be used for DF as well as a range f achros.

A Microstar IV or better yet Diastar platform is a little trickier but some options exist including using 160mm CF opjectives, which are compatible in the system with Reichert Austria objectives. They just give about a 10% increase in mag. Finding a 45mm Reichert 100X with iris is hard but more options of types exist, planfluor and planapo. There is a beautiful 40X oil 1.0 with iris in the Reichert Austria series. Not common but around nonetheless. I bought one from a surplus dealer in Israel recently for 110.00. There is also the 50X .80 oil neoplan without iris but it does not require it for DF as well as the 40X .70 planfluor, a beautiful dry DF objective but being sought after, so prices are a bit high.

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Re: Affordable finite low magnification oil iris objective list

#21 Post by BramHuntingNematodes » Mon Jan 17, 2022 7:36 pm

I seen a couple Polanrets sold for pretty low prices this last year or so considering what a monstrously expensive system it must have been when it was being manufactured. $1,500 or so. As much phase contrast as you could ever want right there.
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Re: Affordable finite low magnification oil iris objective list

#22 Post by zzffnn » Mon Jan 17, 2022 9:15 pm

Thank you, Apochronaut:

What I would ideally like herein are some high NA oil apo iris objectives that I can stop down with iris, for darkfield or variable DIY COL. And ideally I can move them between my two 160TL scopes.

Low NA doesn't work as well for COL for my purpose.

I haven't had much luck getting high NA iris objectives of infinity tube length (even though I like the AO series 10 design quite a bit); the easily available infinity objectives on eBay are achromat low NA ones that costs no less (often time more) than apo iris ones of 160TL.

As reference, I recently bought:

1) a Zeiss Jena NF apo 1.32 iris for about $120 shipped;

2) an old Leitz 8mm apo oil objective that seems to have iris for $30 shipped (haven't received it yet, so hard to tell if it is really an "oel" [seller description] and iris [my eyeballing, which could be wrong]);

3) an AO 214F cardiod darkfield condenser for $46 shipped;

4) Now I am considering two options: (plan)apo 40x - 50x NA 1.0 oil iris 160TL objective for $130 - $220 shipped.

I would like an AO10, but I don't think I can easily get the same high NA objectives at similar cost.

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Re: Affordable finite low magnification oil iris objective list

#23 Post by apochronaut » Tue Jan 18, 2022 1:33 am

Sometimes planapos show up at those prices. Not commonly but dilligence pays off. Keep your eyes peeled. The pickings are getting slim. With the 10/20 they never focused on planapos because the planachros were so good but they did make them. During the series 4 and early series 10/20days, before DF became super popular, they made various objectives of .85 to .95 which don't work for D.F., with the 214F. Then there were a few with iris but all achros or planachros. The 43X apo from 1965 was reduced in N.A. from .95 to .80 and also the later planapo design had a deliberately reduced N.A.
The question I have is : a 40X objective that is corrected as a planapo and is .80 N.A. will work for D.F. A 40X objective that is corrected as a planapo and is .95 N.A. will not work for D.F. ( unless you can find a really high N.A. condenser ...1.20 - 1.40 minimum and that would have to be tested to find out if it works). The high N.A. objective needs to have an iris diaphragm in order to reduce it's N.A. so it can be used for D.F. : reduced to about .80 N.A. . Since you are reducing the N.A. of the .95 objective to .80, why is that better than using a dedicated 40X .80 planapo that works straightaway for DF?

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Re: Affordable finite low magnification oil iris objective list

#24 Post by zzffnn » Tue Jan 18, 2022 4:07 am

Thanks, Apochronaut.

160TL Apo 40x NA 0.80 oil objectives at around $200 USD are slim pickings, aren't they? I do want oil immersion too.

At that range, there are quite a few 40x - 50x ~NA 1.0 oel apo iris objectives from Zeiss and Leitz to choose from. I just need to keep my eyes peeled, as you said.

I like the convenience and flexibility of objective iris control.

I would like to retain the ability of using high NA darkfield on thin and tiny subjects.

For example, Frustulia diatoms (being so small and thin) can be imaged well at darkfield NA of 0.9-1.1. But (big and thick) Surirella diatoms or paramecia would definitely required stopping down to darkfield NA of 0.8 or less, otherwise too much white halos would be revealed.

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Re: Affordable finite low magnification oil iris objective list

#25 Post by Hobbyst46 » Tue Jan 18, 2022 11:23 am

zzffnn wrote:
Tue Jan 18, 2022 4:07 am
But (big and thick) Surirella diatoms or paramecia would definitely required stopping down to darkfield NA of 0.8 or less, otherwise too much white halos would be revealed.
I suspect that the problem with thick large Surirella is depth of field. At least for me, DF stacking leaves too much halo indeed. May I add an example, taken with the planapo 40x1.0 iris oil (reduced NA to ~0.8 I think). Surirella from Hamburg (courtesy MicroBob), mounted in Naphrax.
IMG_6254.JPG
IMG_6254.JPG (70.96 KiB) Viewed 82 times
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Re: Affordable finite low magnification oil iris objective list

#26 Post by apochronaut » Tue Jan 18, 2022 1:59 pm

zzffnn wrote:
Tue Jan 18, 2022 4:07 am


For example, Frustulia diatoms (being so small and thin) can be imaged well at darkfield NA of 0.9-1.1. But (big and thick) Surirella diatoms or paramecia would definitely required stopping down to darkfield NA of 0.8 or less, otherwise too much white halos would be revealed.
You can't achieve DF at N.As. of .9-1.1 with the 214F condenser. That's why AO put an iris in the #1016 50X .85 oil planachro objective. In order to have a dark field, the slide must be under a condition of TIR. There is a condition of dusk that occurs in DF before TIR is reached ; over about a .2 N.A. range where a kind of greyfield with low contrast and resolution muddies the image, caused by scatter and diffraction that limits the contrast. You have to reduce the N.A. until the scatter is eliminated.
With some condensers you can get to a higher N.A. but they need to have a very high minimum N.A. Some are 1.25-1.45. I have even seen one that was 1.3-1.52. I don' t exactly know what the 214F's specs. are but I think 1.15-1.35 is a safe bet.
Later, when AO/Reichert produced the 1096 toric condenser , they built a derivative of the 1016 into 45mm barrels for the series 400 : the 50X oil immersion Neoplan. # 1758 I think it is. It's a little better objective than the 34mm parfocal #1016 but it has an N.A. knocked down to .80 and can be used directly for DF.
At Reichert in Austria, when they designed the objectives for the Unitron and subsequently the Polyvar : they put an iris in all objectives with an N.A. over .75, since they were designing the one set of objectives to be useful with all contrast methods. Even at that, the DF condenser they used had an N.A. of 1.20-1.40. I am not sure but I think in that system DF occurs at .85.
In former times when drop in funnel stops were used, they sometimes would not seat perfectly or get a bit skewed during nosepiece rotation. Spencer decided to build a dedicated 1.8mm 95X achromatic DF objective, the same as the 95X 1.25 objective but housing a permanent N.A. restrictor that limited the N.A. to .85, maximizing the potential N.A. of the objective under DF used with their cardioid condenser.

https://www.ebay.com/itm/203666810016?h ... SwKIdhbDdU Nikon aren't 34mm, they are closer to 33mm.
Last edited by apochronaut on Tue Jan 18, 2022 2:50 pm, edited 1 time in total.

dtsh
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Re: Affordable finite low magnification oil iris objective list

#27 Post by dtsh » Tue Jan 18, 2022 2:47 pm

apochronaut wrote:
Tue Jan 18, 2022 1:59 pm
With some condensers you can get to a higher N.A. but they need to have a very high minimum N.A. Some are 1.25-1.45. I have even seen one that was 1.3-1.52. I don' t exactly know what the 214F's specs. are but I think 1.15-1.35 is a safe bet.
1.15 - 1.25 is what's marked on it.

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Re: Affordable finite low magnification oil iris objective list

#28 Post by apochronaut » Tue Jan 18, 2022 2:59 pm

dtsh wrote:
Tue Jan 18, 2022 2:47 pm
apochronaut wrote:
Tue Jan 18, 2022 1:59 pm
With some condensers you can get to a higher N.A. but they need to have a very high minimum N.A. Some are 1.25-1.45. I have even seen one that was 1.3-1.52. I don' t exactly know what the 214F's specs. are but I think 1.15-1.35 is a safe bet.
1.15 - 1.25 is what's marked on it.
1.15-1.25 sl . th : SLIDE THICKNESS, not N.A. DF requires a slide thickness within certain boundaries.

dtsh
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Re: Affordable finite low magnification oil iris objective list

#29 Post by dtsh » Tue Jan 18, 2022 3:15 pm

apochronaut wrote:
Tue Jan 18, 2022 2:59 pm
dtsh wrote:
Tue Jan 18, 2022 2:47 pm
apochronaut wrote:
Tue Jan 18, 2022 1:59 pm
With some condensers you can get to a higher N.A. but they need to have a very high minimum N.A. Some are 1.25-1.45. I have even seen one that was 1.3-1.52. I don' t exactly know what the 214F's specs. are but I think 1.15-1.35 is a safe bet.
1.15 - 1.25 is what's marked on it.
1.15-1.25 sl . th : SLIDE THICKNESS, not N.A. DF requires a slide thickness within certain boundaries.
I think I knew this at some point and managed to forget it again. A quick scan of the manual didn't yield anything apparently useful so I've got nothing to add.
Thanks!

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Re: Affordable finite low magnification oil iris objective list

#30 Post by zzffnn » Tue Jan 18, 2022 3:46 pm

Thank you very much, apochronaut.

Yes, I did see that short Nikon 40x 0.8 but did not buy it because of its parfocal height. It is doable but too much hassle (I don't have other short Nikons). I can work with 33, 37 (with Leitz Plezy to extend 8mm) and 45mm on the same 5-hole nosepiece. The Nikon is slightly longer than 33mm, if I remember correctly.

I used a Leitz Heine for very high NA darkfield, which is how I got to darkfield NA 1.1.

I did not know 214F is limited to 1.15 (-0.2). I have another two paraboloid darkfield condensers, one from LOMO and one from B&L, but haven't tried them in NA above 0.8-0.85 yet.

Another nice thing with an iris high NA objective is to use it with darkfield condenser in COL mode (though objective iris would have to go above NA 1.2 for 1.2-1.4 DF condenser). This method is more reliable than using a DIY patch stop of the same NA in a phase turret condenser (which in turn betters a condenser whose iris diaphragm cannot be easily assessed).
Last edited by zzffnn on Tue Jan 18, 2022 8:35 pm, edited 1 time in total.

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