How much worse is the phase version of an objective for brightfileld

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pippo1234
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How much worse is the phase version of an objective for brightfileld

#1 Post by pippo1234 » Tue May 11, 2021 9:01 pm

I am in the market for a Nikon CFN 10x achro plan. I can choose between the normal and phase version. The phase version would kill two birds with one stone, but I would not be willing to sacrifice image quality in brightfield given my only occasional use of phase contrast. Is there a free lunch?

Many thanks in advance.

BramHuntingNematodes
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Re: How much worse is the phase version of an objective for brightfileld

#2 Post by BramHuntingNematodes » Tue May 11, 2021 9:09 pm

Just use phase more often
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

PeteM
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Re: How much worse is the phase version of an objective for brightfileld

#3 Post by PeteM » Tue May 11, 2021 9:52 pm

You'd clearly see the difference in an A-B comparison. However, it might not bother you without that direct comparison.

Depending upon what you want to view, if protists and other live and near-transparent cells are foremost among your subjects -- I'm inclined to agree with Bram.

10x is a pretty decent magnification for scanning the field of view and phase contrast will make it easier. You're more likely to do any serious study or imaging at 20x and higher.

Were it a 40x objective, I'd be more particular about absolute image quality and resolution -- and might likely choose the .70 numerical aperture Nikon CFN over phase contrast.

Should you ever have a serious lapse in financial judgement (or a serious interest in amazing images) and decide to add DIC, the Nikon CFN brightfield objectives will work with that. Not so, the phase objectives.

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#4 Post by pippo1234 » Tue May 11, 2021 10:07 pm

Thank you both. Indeed I dream of adding DIC at some point. So that seals it. I do have phase contrast 10x and 40x E acrhro. The convenience woulad have come from having 4x, 10x Ph plan, 20x and 40x plan and 40 Ph on the same nosepiece. I could ditch the 4x and have 10x Ph, 40x Ph and 10x, 20x and 40x plan, but I do use the 4x for scanning. Life is about tradeoffs … or an Optiphot with multiple nosepieces (and eventually DIC). :D

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#5 Post by pippo1234 » Wed May 12, 2021 12:17 pm

With a view to buying objectives that are DIC-ready, it seems that Olympus Splans are much more common, and way cheaper, than Nikon CFNs. Having bought pristine Splan 10X, 20X and 40X for less than the cost of a single CFN I am starting to think that it may be easier/cheaper to get matching WHK10X and NFK3.3 eyepieces for my Labophot 2 rather than try to obtain CFN objectives. Of course, I will stick to my 2 Nikon E Ph to match the Nikon phase contrast converter. Any contraindication I am missing?

TIA

apochronaut
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Re: How much worse is the phase version of an objective for brightfileld

#6 Post by apochronaut » Wed May 12, 2021 1:11 pm

I have pretty extensive experience using phase and BF in the same microscope. When one is looking to improve the detail of what they are seeing through the microscope, phase is a natural jump but it doesn't really make sense to make that jump for one objective magnification unless you happen upon a condenser objective pair that includes only a diaphragm and objective. In your consideration of buying a 10X CFN phase objective; do you have a phase condenser to go with it?

In microscopes I use for which I have BF/phase interchangeability the pattern of evolution in terms of contrast and resolution goes : achromat>>>phase achromat>>>phase achromat of a more suitable contrast method or DF achromat>>>
fluorite>>>phase fluorite>>> apochromat and phase apochromat or DF apochromat. Always, will the erasure of diffraction improve imaging but often, if there must be a choice between the two, the erasure of chroma will account for a greater improvement, so often an apochromat is preferred over a phase achromat.

In my opinion, it makes more sense to pursue the sourcing of higher colour corrected objectives and a versatile and well corrected condenser, than holding out for DIC at high cost. You can achieve much of the benefit of DIC with inexpensive oblique techniques but it helps to have a good condenser to work with.

Since your microscope is a 160mm and D.I.N., you have a lot of choices. I would be looking for planapos outside of the Nikon , Olympus stable, where you could probably get 3 for the price of 1.

and with regards to DIC, PZO DIC objectives go for peanuts comparatively. They have built in Wollaston prisms. The PZO or any other slit condenser below the stage with polarizers top and bottom would be a credible DIC system. The same form as covered in the PZO DIC manual. Granted , PZO only ever made planachros but they are 45mm parfocal and you can often land a set of 4 for 200.00. You aren't going to be graduating to planfluor or planapo DIC any time too soon, since one objective will be at least 300.00, usually.

PeteM
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Re: How much worse is the phase version of an objective for brightfileld

#7 Post by PeteM » Wed May 12, 2021 1:27 pm

I'd be inclined to bide your time and look for a Nikon Optiphot with the CFN objectives. The regular CF plan achros are also pretty good and often cheap if you want some magnification right now. Even the CFN Plan Apos are sometimes affordable.

Starting from scratch either the Nikon or Olympus are fabulous systems. However, you're already well into the Nikon world and the Nikon chrome-free designs open up more options for matching cameras to your system. DIC will also likely be easier to find for less than both an arm and a leg with Nikon and (in my limited experience) be a tiny bit better than the Olympus finite system.

My experience is that the SPlan and CFN objectives will be similarly priced over the long haul. Ebay asking prices seem to depend on what others are charging. So some items with relatively limited availability may sit with no sales but sellers hoping for 2x the value. Then someone comes up with a fairly-priced buy-it-now and prices adjust.

Don't just search for "CFN" though. Some sellers will wrongly label any Nikon finite objective that way and relatively few will call it out since it is not part of the stenciled label.

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#8 Post by pippo1234 » Wed May 12, 2021 6:12 pm

Thanks! I really appreciate all the info. It is not always obvious were to look for this kind of knowledge.

For the record, I have a Nikon Phase Contrast-2 1.25 condenser which allows me to easily switch between BF, DF and phase, hence the advantage of having both BF and phase objectives on the same nosepiece. As I wrote above, I am unclear about what is a better and versatile condenser for the optiphot/labophot family (the Nikon Ach Apl 1.4 does not seem versatile). Apart from objectives and eyepieces, compatibility across brands is definitely a mystery to me.

apochronaut
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Re: How much worse is the phase version of an objective for brightfileld

#9 Post by apochronaut » Wed May 12, 2021 7:12 pm

Phase condensers are optimized for use as a dry condenser when used for phase but can be also used dry or oil immersed for objectives with N.A.s greater than 1., if they also carry an N.A. greater than 1. For use with achromats or plan achromats, both in phase and BF, it sounds like your condenser is fairly close to ideal. It would be limited in DF to 40X max., likely.

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#10 Post by pippo1234 » Wed May 12, 2021 7:30 pm

I am quite happy with the condenser but I’d rate it marginal for DF at 40x. I am planning to experiment with a home made DF filter for 40x.

BramHuntingNematodes
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Re: How much worse is the phase version of an objective for brightfileld

#11 Post by BramHuntingNematodes » Wed May 12, 2021 7:57 pm

I've gotten good COL with a 40x with stops, but never real df. You will need a special condenser.
1942 Bausch and Lomb Series T Dynoptic, Custom Illumination

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#12 Post by pippo1234 » Wed May 12, 2021 8:39 pm

To be fair, the condenser is ok for df with a 40x,0.65. 40x,0.7 is definitely marginal.

Phill Brown
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Re: How much worse is the phase version of an objective for brightfileld

#13 Post by Phill Brown » Tue May 25, 2021 6:49 pm

Where Nikon Labophot/Labophot 2 stages are slotted for condenser they are not all the same. Parts can get swapped around.
18mm wide or 25mm wide slot. 18mm slot version may not work properly for Phase contrast 2 1.25 condenser.
Lens contacts the stage before the stop,sub optimal, with phase objective noticeable patchy dark field effects in center field.
Worth knowing which stage is fitted.

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#14 Post by pippo1234 » Tue May 25, 2021 9:05 pm

Wow, the depth of knowledge on this forum never ceases to amaze me!

I think you mean the width of the central slot in the stage. I measure 21mm with a caliper.

Many thanks,
Giulio

Red_Green
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Re: How much worse is the phase version of an objective for brightfileld

#15 Post by Red_Green » Tue May 25, 2021 9:55 pm

I have no expeieriance with Nikon objectives. I have the Amscope phase kit. Before that I was using the stock Amscope objectives. When I installed the phase plan objectives they were outstandingly far better than the stock objectives. Everything bout them was better. Except for whatever reason phase objectives do not have spring loaded noses which sucks.

apochronaut
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Re: How much worse is the phase version of an objective for brightfileld

#16 Post by apochronaut » Wed May 26, 2021 12:57 pm

The concern gets raised a lot about whether phase objectives can be used in BF. Yes but there will be spherical aberration due to the phase ring in the objective.
If you are not detail focused, that might not matter much but phase objectives used in BF mode cannot provide the contrast/resolution quotient that standard objectives will. In general within any class of objectives , i.e. achromat, fluorite, apochromat, if both BF and phase condensers are available going from the less resolved and contrasty to best resolved and contrasty imaging goes : phase objective in BF>>>>BF objective in BF>>>>Phase objective in phase. There is also the possible use of BF objectives with various phase condenser diaphragms which when adjusted appropriately can yield anything from decent DF to DIC like oblique to a form of enhanced contrast BF or a kind of quasi-phase.

With each jump in objective colour correction a whole different circumstance exists. In general, I find that a BF apochromat usually can reveal fine details better than an equivalent magnification achromat phase objective but that is likely due to the enhanced N.A. that apochromats carry within their workings. Enhanced contrast cannot overcome a resolution reduction due to an inadequate N.A.

pippo1234
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Re: How much worse is the phase version of an objective for brightfileld

#17 Post by pippo1234 » Sun Jun 13, 2021 7:00 am

My experience is that the SPlan and CFN objectives will be similarly priced over the long haul.
Pete, I just wanted to thank you for that. It was not my experience on Ebay UK where CFs are as rare as hen teeth and ridiculously expensive. Your remark prompted me to try Ebay.it where there are plenty of international sellers of CFs which for some reason do not appear on Ebay.uk.

I have now bought 10x, 20x and 40x plan achro CFNs at prices comparable to Splans and am most happy with.

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