160/-, planaapo low mag. objectives...please advise?

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charlie g
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160/-, planaapo low mag. objectives...please advise?

#1 Post by charlie g » Thu Mar 07, 2019 9:22 pm

High all, for years I've sensed with wetmount live organism slides..my 4X and 10X plan objectives offer similar crisp images with phase 1, and DF contrast methods.

Like a lot of live organism observers...I have collected a few planapo higher mag objectives. Today I ask..with Planapo 4X/0.14, 160/-, and Planapo 10X/ 0.32, 160/- objectives...am I defeating the planapo correction by use of these on wetmounts with coverslips? Am I defeating planapo correction by (160/-) use of these with raw water droplets on a microscope slide..due the curvatures of the water column about that wetmount slide?

Are most (-) speced planapo low power objectives only for extremely flat slide preps ( blood smears, bacteria smears,spore smears, fecal smears etc.)? Or are wetmount pond droplet slides compatible with the planapo correction? We ( me that is) rarely oil-bridge my slide bottoms to the 1.25 NA condenser, even as I enjoy both my water and oil-immersion optics. I crouch beside the weasel language I've read in microscope mauals that..'to not oil the condenser to the slide often sensible, as contrast is often a better part of resolution..you may loose contrast in live specimens with a complete oil-bride top and bottom of slide.

Are 4X and 10X planapos speced: '160/-' seriously compromised by use with coverslips? Any comments welcome. Charlie guevara

Hobbyst46
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Re: 160/-, planaapo low mag. objectives...please advise?

#2 Post by Hobbyst46 » Thu Mar 07, 2019 9:49 pm

charlie g wrote:High all, for years I've sensed with wetmount live organism slides..my 4X and 10X plan objectives offer similar crisp images with phase 1, and DF contrast methods.

Like a lot of live organism observers...I have collected a few planapo higher mag objectives. Today I ask..with Planapo 4X/0.14, 160/-, and Planapo 10X/ 0.32, 160/- objectives...am I defeating the planapo correction by use of these on wetmounts with coverslips? Am I defeating planapo correction by (160/-) use of these with raw water droplets on a microscope slide..due the curvatures of the water column about that wetmount slide?

Are most (-) speced planapo low power objectives only for extremely flat slide preps ( blood smears, bacteria smears,spore smears, fecal smears etc.)? Or are wetmount pond droplet slides compatible with the planapo correction? We ( me that is) rarely oil-bridge my slide bottoms to the 1.25 NA condenser, even as I enjoy both my water and oil-immersion optics. I crouch beside the weasel language I've read in microscope mauals that..'to not oil the condenser to the slide often sensible, as contrast is often a better part of resolution..you may loose contrast in live specimens with a complete oil-bride top and bottom of slide.

Are 4X and 10X planapos speced: '160/-' seriously compromised by use with coverslips? Any comments welcome. Charlie guevara
At least with Zeiss as well as Olympus objectives, the "/-" mark means either with or without coverslip, whereas the "/0" mark means without coverslip.
BTW, I have three high-mags: Two Planapos, 100X/1.3, 63X/1.4, and a Neofluar 63X/1.25, all of them are 160/-. I hope this contributes.
Last edited by Hobbyst46 on Thu Mar 07, 2019 9:59 pm, edited 2 times in total.

charlie g
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Re: 160/-, planaapo low mag. objectives...please advise?

#3 Post by charlie g » Thu Mar 07, 2019 9:56 pm

Thanks for that info! I forgot about: (/-) spec being with or without. I'm impressed that planapo level of correction can be so flexible...but then too..these are low mag objectives I'm asking about. thanks for this info. Charlie g

abednego1995
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Re: 160/-, planaapo low mag. objectives...please advise?

#4 Post by abednego1995 » Fri Mar 08, 2019 12:46 am

Well, as a rule of thumb if you're using objectives with NA lower than 0.4 it wouldn't matter much whether you have a coverslip or not. It applies for any objective.

The catch with Hobbyst46's objectives, is that they are both immersion objectives.
As long as the refractive index of the coverslip and oil is matched, and the WD allowing, oil immersion objectives don't care about coverslips.
(Yes, I know there are immersion objectives with 0.17 coverslip indication, but that statement is for keeping the WD within limits. Plus, dispersion parameters are different with oil and glass so with very highly corrected objectives they might specify the right coverslip thickness.)

However, if you are going to do wetmount imaging, dry planapos above NA0.4 and oil immersion planapos will have trouble with SA for deep objects far from the bottom of the coverslip since they are not corrected for the refractive index of water.
(It's not impossible, but not optimal. Low NA planapos should work OK)
For wet mounts, dipping and water immersion objectives are the holy grail. Very rare to find, but they work like magic.

Cheers,
John

apochronaut
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Re: 160/-, planaapo low mag. objectives...please advise?

#5 Post by apochronaut » Fri Mar 08, 2019 1:07 am

The only things I would add to that nicely worded explanation is that objectives vary somewhat in their sensitivity to the immersion medium used, whether it be air or liquid, even at identically defined N.A.'s. As a rule of thumb, I test objectives I am going to be using under a group of conditions, just to see how they do. I have seen objectives as high as .85 that are surprisingly insensitive to the immersion medium and one's as low as .4 that are more sensitive.

It has to do with the internal spacing of the elements, I believe. Compact constructions yield lower levels of sa.

Generally, if it has a hyphen where the cover slip spec. should be , it is pretty immune to the cover and if it has a 0 it is very sensitive to any cover. For aqueous samples with oil immersion objectives, in general that .17 should be regarded more as sample thickness rather than cover slip thickness.

ChrisR
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Re: 160/-, planaapo low mag. objectives...please advise?

#6 Post by ChrisR » Fri Mar 08, 2019 1:33 am

Darn it.. I posted earlier , I thought, but it's not here.

At NA 0.4 you're on the cusp of significance

The question is answered in a current thread in the other place :
http://www.photomacrography.net/forum/v ... hp?t=34610

Thorlabs graph:
Image

charlie g
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Joined: Mon Oct 20, 2014 7:54 pm

Re: 160/-, planaapo low mag. objectives...please advise?

#7 Post by charlie g » Fri Mar 08, 2019 2:43 am

Thank you Chris R, John, and aponaut ( in no special order..all informative to me)...ah yes the forgiving optical performance with NA under 4.0, and the nature of the symbols: '/-' meaning with, or with out a coverslip...the 4X and 10X planapos should function with my live protist and meiofauna wetmount slides.

Now to see if this pair I'm close to purchasing...will as the low mag/ low NA objectives they are...be notably better in performance than my Plan 4X, Plan 10X.

Thanks all for your shared microscopy, it betters my microscopy. Charlie Guevara, finger lakes/US

apochronaut
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Re: 160/-, planaapo low mag. objectives...please advise?

#8 Post by apochronaut » Fri Mar 08, 2019 3:31 am

ChrisR wrote:Darn it.. I posted earlier , I thought, but it's not here.

At NA 0.4 you're on the cusp of significance

The question is answered in a current thread in the other place :
http://www.photomacrography.net/forum/v ... hp?t=34610

Thorlabs graph:
Image

I know that there is lots of information on that : I've seen the Thorlabs graph and others and it makes perfect technical sense but it isn't true for certain objectives, when it comes to immersion mediums. For them the line isn't linear. I can put two oil immersion .80 objectives I know of, side by side in two identical microscope stands then switch them to water immersion or air and one of them will outperform the other by a country mile when used with the unspecified immersion media. N.A. isn't the whole picture, when it comes to an objectives response to what is between it and the sample. The Thorlabs graph holds true for objectives designed to similar performance characteristics but objectives designed otherwise can vary from that graph to more or less of a degree.

abednego1995
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Re: 160/-, planaapo low mag. objectives...please advise?

#9 Post by abednego1995 » Fri Mar 08, 2019 4:58 am

I totally agree.
There would be specific design criteria for each objective, and that would mean different residual SAs for each.

One thing I've yet to experiment myself is testing objectives at different wavelengths in respect to SA.
I'm suspecting that if you use an objective in a wavelength other than it's SA is corrected for, it will give over or undercorrected SAs. If that deviation would cancel the SA introduced by index mismatch it would produce acceptable images.

Any insights?

Cheers,
John

Hobbyst46
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Re: 160/-, planaapo low mag. objectives...please advise?

#10 Post by Hobbyst46 » Fri Mar 08, 2019 10:25 am

abednego1995 wrote:The catch with Hobbyst46's objectives, is that they are both immersion objectives.
As long as the refractive index of the coverslip and oil is matched, and the WD allowing, oil immersion objectives don't care about coverslips.
(Yes, I know there are immersion objectives with 0.17 coverslip indication, but that statement is for keeping the WD within limits. Plus, dispersion parameters are different with oil and glass so with very highly corrected objectives they might specify the right coverslip thickness.)
Thanks Abednego and others for the explanations.
I hope this is not a serious distraction from the original question in the thread, just a small addendum. A comparison between the specifications in the "Zeiss Optical Systems" document, and some high-mag, high NA immersion objectives:

Z. O. S. document:
NEOFLUAR, 63x,1.25 NA, Oil ,Ph3,...,WD 0.65 mm, Coverslip 0.17mm, Cat No. 461821
Planapochromat, 63x,1.4 NA, Oil ,Ph3,..., WD 0.09 mm, Coverslip 0.17mm, Cat No. 461841
Planapochromat, 100x,1.3 NA, Oil ,Ph3,...,WD 0.09 mm, Coverslip 0.17mm, Cat No. 461941

"My" actual Zeiss 160mm objectives
NEOFLUAR, 63x,1.25 NA, Oil ,Ph3,...,Coverslip (-), Cat No. 461821-9903
Planapochromat, 63x,1.4 NA, Oil ,Ph3,..., Coverslip (-), no Cat No.
Planapochromat, 100x,1.3 NA, Oil ,Ph3,...,Coverslip (-), Cat No. 461941-9903

So these are of a different design than the catalogue items.

1. Are they expected to be "better" in any sense from the 0.17mm coverslip version, apart from being "newer" (perhaps?).

2. Assuming that that I use immersion oil, intuitively, if the coverslip can be omitted (dry smear, etc) then working without coverslip should provide less SA, since each optical element is liable to introduce aberrations (even if the thickness is 0.1700mm). Is this true ?

apochronaut
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Re: 160/-, planaapo low mag. objectives...please advise?

#11 Post by apochronaut » Fri Mar 08, 2019 12:15 pm

Do you know if there is a difference in the recommended condenser for the two different sets of objective cat.#'s? Condenser design can do some strange things. Or are the objectives specified for different applications?. Or is it just a case of Zeiss choosing to clarify their designation or follow a different convention at some point?
For question # 2: The phrase homogeneous immersion has largely disappeared from objective specifications these days but what you are describing begins to approach that. One would assume that the specification of a .17 cover slip with oil immersion is there to provide a specific w.d. and that somewhere in there is the further assumption of an unhomogeneous immersion or something under the cover slip with a different refractive index, since the oil and glass used are supposed to be within a hair of having the same n.

Hobbyst46
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Re: 160/-, planaapo low mag. objectives...please advise?

#12 Post by Hobbyst46 » Fri Mar 08, 2019 1:57 pm

Thanks apochronaut,
apochronaut wrote:Do you know if there is a difference in the recommended condenser for the two different sets of objective cat.#'s? Condenser design can do some strange things. Or are the objectives specified for different applications?. Or is it just a case of Zeiss choosing to clarify their designation or follow a different convention at some point?.
Sorry, I do not have answers. The various condenser descriptions do not mention a specific objective (w/wout coverslip, dry/water, etc). The coverslip-less objectives are not even mentioned there - perhaps they are from a more modern generation, for which I have no literature.
apochronaut wrote:For question # 2: The phrase homogeneous immersion has largely disappeared from objective specifications these days but what you are describing begins to approach that. One would assume that the specification of a .17 cover slip with oil immersion is there to provide a specific w.d. and that somewhere in there is the further assumption of an unhomogeneous immersion or something under the cover slip with a different refractive index, since the oil and glass used are supposed to be within a hair of having the same n.
The WD notion, mentioned also by abednego1995 above, sounds plausible. Maybe worth a small test: Invent a flat specimen that can be repeatedly prepared with or without water+coverslip, use oil in both cases and compare...

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