PlanF objectives

Everything relating to microscopy hardware: Objectives, eyepieces, lamps and more.
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apochronaut
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PlanF objectives

#1 Post by apochronaut » Fri Jun 24, 2022 1:15 am

I have done a little more sleuthing into the PlanF objectives that are around various places. I also have done some testing on them , so can report a little on their performance.
One of the things that is a bit of a mystery is that there are both PlanF and Plan Fluor objectives coming out of China. To complicate matters, there are also PlanF and semi-apo objectives coming out of India.
In this little piece I will deal only with the PlanF and in comparison to one another and other objectives as a yardstick. I tested both the Chinese PlanF 40X .75 and the Indian PlanF 40X .75 against a Reichert Planachro 40X .66 and a Reichert Planfluor 40X .70. in the same stand using a set wide field eyepieces that perfectly corrected for the PlanF objectives (Olympus 180mm reference length format) and another set that perfectly corrected for the Reichert objectives. There is a very slight difference between the Olympus and Reichert systems.
The Reichert objectives are fairly typical for their types giving very well corrected images with excellent resolution. The 40X .70 planfluor in fact punches well above it's weight, with imaging that rivals a planapo and as well seeming to have a higher N.A. than it does. It has a good working distance allowing for haemocytometer use.

The two PlanF objectives are similar but not the same.
The Chinese version has larger diameter front and rear lenses and a wider optical tube when looking through the objective. It has a removable chrome shroud with painted data. The front lens is concave. The rear diaphragm is a threaded in knurled disc.
The Indian PlanF has an almost identical chrome barrel but with lightly engraved data. It doesn't seem to have a removeable shroud, although it just might be tight. It too has a concave front lens.The rear diaphragm is a threaded
in metal disc removeable with a pin wrench.

From a distance the two objectives look almost identical.

Performance
----------------------- Both of the PlanF objectives perform a cut above a planachromat. They are clearly not just a Planachro rebadged or a strain free version of a planachro. Do they perform like a planfluorite though : the criteria of which would be higher resolution, truer colours, better colour correction, better contrast and of course complete planarity? Normally too, they should have a shorter w.d. than the Reichert Planachro, which is about as good as most modern good quality Planachros
Well, yes and no. The Chinese PlanF resolves about as good as the Reichert Planachro but has a slight edge when it comes to colour correction. It is just ever so slightly not an achromat. Contrast is about the same and colour rendition is maybe slightly superior. Planarity is full with a flat field.

Given the smaller diameter lenses of the Indian PlanF, I expected it to be outperformed by the Chinese version but I was pleasantly surprised when it bore comparison to the Reichert Planfluor , rather than the Planachro. Although the Reichert is clearly superior in all ways, the Indian PlanF is obviously not in the Planachro league anymore. In comparison to the Chinese PlanF all measurement criteria are better with the resolution about midway between it and the Reichert Planfluor.

An odd thing about both the PlanFs is that they both have a much greater working distance than either of the Reichert objectives.
One lacking aspect of oriental objectives in general is that they are usually pretty sketchy when it comes to parcentering and I am sorry to say that both the PlanFs are no exception..

So. In short, if you can land a deal on one of these and I would endorse the Indian version, and you have a system and eyepieces they can work in, especially to ensure planarity and edge to edge colour correction : not too bad, especially the Indian version.
I will try to post some pictures later, if I get a chance.

GerryR
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Re: PlanF objectives

#2 Post by GerryR » Fri Jun 24, 2022 11:14 am

Excellent detail as usual! Just curious what instrumentation do you use in your evaluations. I have always been curious, especially in color renditions, as to how comparisons are made. I know in photography we have master color charts, e.g. Tiffen Color Separation Guide and Grey Scale. Are there similar "slides" for microscope image evaluations?

apochronaut
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Re: PlanF objectives

#3 Post by apochronaut » Fri Jun 24, 2022 12:32 pm

I think that would be hard to do with microscope samples, since there are so many variables that could affect colour : lighting sources, sample thickness, stains if any, filters if any etc.
In my case it is purely subjective based on experience with the control objectives and others. I use several better colour corrected 40X objectives for BF fairly routinely. A 40X .80 planapo, a 40X 1.0 oil planapo and the 40X .70 planfluor, so I have a baseline of their performance characteristics as well as relative to each other. The 40X .66 planachro I also use but less so. I included it in the test because I considered it as a minimum performance yardstick whereas the planfluor 40X .70 was the maximum performance yardstick. I know their colour correction, colour rendition, contrast, resolution etc. characteristics well.
In comparing the two PlanF versions, I was expecting or rather would have been happy with performance in between those yardsticks and the judgement was purely subjective. I did not anticipate performance better than the Reichert 40X .70 Planfluor. That would have been a big surprise.
If a scale of 1 to 10 was used , where the 40X .66 planachro was a 1 and the 40X .70 planfluor was a 10 : the Chineee PlanF would be a 3 and the Indian PlanF would be a 6.5 in overall performance but I do weigh resolutiion higher than colour rendition for instance. Resolution is also partially controlled or maybe affected is a better word by contrast and colour correction. Better resolution therefore usually implies, better contrast and better colour correction.

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: PlanF objectives

#4 Post by apochronaut » Fri Jun 24, 2022 4:55 pm

An amendment to the shroud design on the Indian objective. It is left hand thread. Kind of hard to remove counter clockwise.

Scarodactyl
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Re: PlanF objectives

#5 Post by Scarodactyl » Fri Jun 24, 2022 6:59 pm

Thanks for the info! I'll have to keep an eye out for a 10x for my petrographic scope.

apochronaut
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Re: PlanF objectives

#6 Post by apochronaut » Wed Jun 29, 2022 8:46 am

I looked in various places but no 10X PlanF shows up at Radical.
Back in the winter the website said "permanently closed" but they still were selling online. Possibly, they closed physically due to Covid and stock ran down.
After an inquiry , they emailed and indicated that they are in a new production of PlanF, which they also call semi-apo. 3 week time frame.

Sansub2
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Joined: Wed Oct 20, 2021 3:34 pm

Re: PlanF objectives

#7 Post by Sansub2 » Wed Jun 29, 2022 5:02 pm

Hi Phil, thanks for the detailed info ( as always). Learning alot from your posts. Noob question, I assume Flutor function is different from water immersion? One is for color correction (Flutor) and another for spherical correction and help look into deeper in water column (WI)?

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: PlanF objectives

#8 Post by apochronaut » Wed Jun 29, 2022 8:55 pm

Yes. Genarally too F, Fluor, Fuotar, Fluorite or sometimes dubbed semi-apo ojectives are engineered to attain a higher N.A., so typically contrast and resolution are superior too.
N.A. is in fact a separate function, so it is entirely possible to make a 1.4 N.A. achromat. It's just that at the theoretical 1400X magnification it would be capable of, ca would obscure enough detail that the purpose would be lost.

Sansub2
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Re: PlanF objectives

#9 Post by Sansub2 » Wed Jun 29, 2022 9:21 pm

Thanks. So, if I am primarily working with pond water, WI objective is better than PlanF ( or combined - superior)? PlanF alone is good if I have a thin sample?

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: PlanF objectives

#10 Post by apochronaut » Thu Jun 30, 2022 12:55 am

Water samples can be pretty thin or pretty thick. It depends on your technique of slide preparation and or what is in the water. I have used oil immersion with good success but only with very thin covers so that the total wss as close to .17/.18 as possible. Having water immersion does give more latitude. for sample depth.
The dry .75 planfluor objectives from India have longer than expected working distances. I have used the AO/Reichert 40X .70 planfluor for pond water in the past quite s bit and it has quite decent w.d. for such a good objective, .48 mm , so you can be a bit sloppy. The Indian PlanF obectives were not entirely consistent in their w.d. but both were greater than the Reichert Planfluor, so should work nicely in any Olympus format infinity stand.

For high magnification , water immersion is definitely the way to go. The 100X 1.15 Olympus format ftom China aren't too expensive and there is also an Indian PlanF 100X 1.2 W.I. at close to twice the ticket. ; about 650.00 $CDN.

Currently I am tracking down the availability of an infinity corrected 60X 1.2 N.A. w./iris W.I. planapo. I am thinking $$$$ for that but what would the big 4 want for one of those.

Sansub2
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Joined: Wed Oct 20, 2021 3:34 pm

Re: PlanF objectives

#11 Post by Sansub2 » Thu Jun 30, 2022 2:46 am

Thank you so much Phil. Really appreciate the detailed response.

apochronaut
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Joined: Fri May 15, 2015 12:15 am

Re: PlanF objectives

#12 Post by apochronaut » Wed Jul 06, 2022 11:45 pm

I finally had a few moments to make some quick photos of the two versions of the 40X .75 N.A. PlanF.

1) The Chinese made PlanF ( painted barrel ) is on the right and the Indian made PlanF ( engraved barrel) is on the left.
2)Picture two shows the optical tube viewed from the rear, with the Chinese objective having a considerably larger aperture.
3) In picture 3. when viewed from the front, the aperture size relationship is reversed.
4) The objectives with the shrouds removed. The indian objective has a much finer left hand thread.
5) The nicest modern cannister housed the Indian objective. Thicker plastic and an aluminum threaded insert in the cap. If you needed an R.M.S.thread for something, that insert might work. The cannisters are in reverse order, Indian on right.
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