Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

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Hobbyst46
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Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#1 Post by Hobbyst46 » Fri Jul 12, 2019 9:56 pm

How does a new unbranded 4X Plan objective perform on a Zeiss Standard microscope ?

My low magnification 160mm TL Zeiss objectives are 2.5 Plan, 3.2X achromat, 6.3X Plan, 10X0.22 Plan, 10X0.30 Neofluar. The 3.2X is very very old and is not parfocal with the others, so I do not use it. The 6.3X is also old and its working distance is extremely short. So I considered getting a 4X of respectable WD. My Zeiss photography setup is afocal, by means of a 8X KPL normal viewing eyepiece.

AFAIK, there are no Zeiss 4X objectives for the Standard. A Leitz objective would cost around 80-100 USD; LOMO, which are rumored to be Zeiss-compatible, are rare and quite costly as well. My experience with Olympus (10X SPlan) and Nikon (4X Plan, not CF) objectives is that they produce a lot of CA on the Zeiss.

So, I thought, why not try an unbranded 4X Plan Chinese objective? Several recent test reports on this respectable Forum and elsewhere provided mixed opinions, about Amscope or unbranded 4X, Plan, or infinity Plan objectives. I decided, against all reason, to risk just ~20 USD including shipping and tax, and opted for an unbranded new 4X/0.1, 160mm Planachromate from China, as shown in the photo below. Its WD is ~13-15mm, much better than the ~3mm WD of my 6.3X objective.

Tests on a stage micrometer are problematic when the target grid is too small and occupies a small fraction of the FOV. So, my current test specimen is the 0.1mm spaced ruler on a spare eyepiece reticule. I compared the new 4X newcomer to the old 2.5, 6.3, and 10X objectives. All tests were done without condenser, to fill as much as possible. The camera catches about 80% of the FOV seen through the eyepieces. Post processing included subtle rotation (to make the ruler horizontal), background brightening and resizing (no crop). I also split the image taken with the unbranded 4X objective into channels.

Frankly, I did not expect much from the unbranded objective, given the known specific aberration corrections of the finite Zeiss optics.
Yet, the image from the 4X, relative to the other objectives, is worse than I had imagined:

1. Considerable CA except in the very center point of the image.
2. Poor planarity, especially shown in the Blue channel. Even worse than that of the simple 10X0.22 Zeiss achromat (although this maybe not a strictly proper comparison).
I guess that the two issues are interrelated.
3. Severe vignetting for some reason.

Perhaps the aberration corrections of the unbranded 4X0.1 objective are tailored to fit Olympus or Nikon (or other scopes) finite optics, and the above poor results are specific to Zeiss setups.
I note that the 4X was not parfocal with the other objectives, the deviation being about 2mm vertically, but I am doubt that this small issue is significant, relative to the other problems.

All comments and criticism are welcome.
Attachments
unbranded 4X plan objective.jpg
unbranded 4X plan objective.jpg (100.13 KiB) Viewed 1599 times
Unbranded 4X0.1 Planachromat (3).JPG
Unbranded 4X0.1 Planachromat (3).JPG (168.43 KiB) Viewed 1599 times
Zeiss 2.5X0.08 Planachromat (1).JPG
Zeiss 2.5X0.08 Planachromat (1).JPG (137.89 KiB) Viewed 1599 times
Zeiss 6.3X0.16 Planachromat (1).JPG
Zeiss 6.3X0.16 Planachromat (1).JPG (171.32 KiB) Viewed 1599 times
Zeiss 10X0.22 Achromat (1).JPG
Zeiss 10X0.22 Achromat (1).JPG (139.09 KiB) Viewed 1599 times
Last edited by Hobbyst46 on Fri Jul 12, 2019 10:21 pm, edited 1 time in total.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#2 Post by Hobbyst46 » Fri Jul 12, 2019 10:00 pm

(continued) Zeiss 10X0.30 Neofluar image. Then, the 4X0.1 Planachromate images, split into Red, Green and Blue channels.
Attachments
Zeiss 10X0.30 Neofluar (1).JPG
Zeiss 10X0.30 Neofluar (1).JPG (190.76 KiB) Viewed 1596 times
Unbranded 4X0.1 Planachromat (3).JPG (red).jpg
Unbranded 4X0.1 Planachromat (3).JPG (red).jpg (46.36 KiB) Viewed 1596 times
Unbranded 4X0.1 Planachromat (3).JPG (green).jpg
Unbranded 4X0.1 Planachromat (3).JPG (green).jpg (43.14 KiB) Viewed 1596 times
Unbranded 4X0.1 Planachromat (3).JPG (blue).jpg
Unbranded 4X0.1 Planachromat (3).JPG (blue).jpg (45.91 KiB) Viewed 1596 times
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#3 Post by MichaelG. » Fri Jul 12, 2019 10:21 pm

Thanks for sharing your test ... and sorry the objective gives disappointing results.
I think you need to try some different eyepieces, to give it the chance to redeem itself.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#4 Post by Hobbyst46 » Fri Jul 12, 2019 10:33 pm

MichaelG. wrote:Thanks for sharing your test ... and sorry the objective gives disappointing results.
I think you need to try some different eyepieces, to give it the chance to redeem itself...
Thanks, Michael. In fact, I gave it a chance: my viewing eyepieces are Olympus WHK (donated by a colleague, from a retired BH-2 stand). Looking through the eyepieces, with the unbranded 4X objective, the ruler marks seem to shine in a purplish-violetish tint! instead of black or very dark grey.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#5 Post by zzffnn » Fri Jul 12, 2019 11:52 pm

@Hobbyst46,

You may want to buy the exact 4x Amscope objective from the exact seller to make sure it is the good one:
https://www.closeuphotography.com/seven ... objective/

Also note that Robert OToole used it without eyepiece (direct projection onto sensor).

LOMO 3.7x likely won't work for you either, as it has very long working distance and is not parfocal with other LOMOs. I would think its parfocal distance is a bit longer than 45mm as well, but am too busy to test it now. Do you want me to test it for you next Tuesday or so?

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#6 Post by PeteM » Sat Jul 13, 2019 3:01 am

Having just received (as in earlier today) the exact same 4x plan import to fill out one of our scopes, I did a quick comparison. Subjective comparison of image quality in the center and evidence of chromatic aberration (orange tint) seen at the field stop borders:

Olympus A4 (cheapest Olympus achro) - OK central image, significant aberration at edge
Import Plan Achro (as above) - Same or better central image as A4, ever so slightly more aberration at edge
Nikon E4 (achro) - Somewhat better than both the above in image and aberration at field limit
Olympus SPlan 4x - Markedly better in all respects - the only "night and day" difference in this comparison

Also found I need to slightly adjust my condenser mount on this scope - ever so slightly tilted.

For the price, the import 4x seems OK; especially for sorting and scanning slides. Photos using just the central portion might also be decent. But my version of an identical-looking objective also showed a lot of chromatic aberration at the edges. I was using an Olympus stand and WHK 10x eyepieces.

Note that the Nikon 4x was a decent performer, despite whatever Olympus corrections might be in the eyepieces.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#7 Post by ImperatorRex » Sat Jul 13, 2019 4:27 am

Hobbyst46 wrote: ...
AFAIK, there are no Zeiss 4X objectives for the Standard.
....
Well, actually there is a Zeiss Planapochromat 4/0,16. Very nice images, however working distance is only 2,5 mm compared to 4,9 mm of the Zeiss Planachromat 6,3/0,16. The Planapochromat 4/0,16 is occasionally sold on ebay, however often has delamination. I have also one with delamination on the back lense, however it still produce excellent results.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#8 Post by 75RR » Sat Jul 13, 2019 5:48 am

Have seen them on ebay from time to time.

I have not managed to pick one up yet, still waiting for one at a price that happily coincides with my variable available funds.

Having said that, a quick search shows that I have missed one that did coincide :(

https://www.ebay.co.uk/itm/Carl-Zeiss-x ... 4301653618
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Zeiss finite 160 Planapochromats.png
Zeiss finite 160 Planapochromats.png (194.45 KiB) Viewed 1536 times
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#9 Post by Scarodactyl » Sat Jul 13, 2019 8:12 am

Zeiss made a plan 160/- zoom objective, 1.6x-5x. Quite a cool piece of hardware.
Edit: here is one on the 'bay https://rover.ebay.com/rover/0/0/0?mpre ... 3109847087
I had one briefly. My own brief testing seemed to produce a great image, though the wd varied with zoom (take both with a grain of salt as it was on a misaligned b&l scope).

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#10 Post by 75RR » Sat Jul 13, 2019 8:59 am

Zeiss made a plan 160/- zoom objective, 1.6x-5x.
Saw one of those but it was too rich for a "just curious" purchase

https://www.ebay.co.uk/itm/Zeiss-Micros ... 3844507037
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#11 Post by Hobbyst46 » Sat Jul 13, 2019 1:26 pm

Thanks all for your kind and helpful remarks !
I should have clarified that the WD of the objective is important in this case, because I am experimenting with top illumination, by means of a LED ring around and near the objective tip.
zzffnn wrote:...You may want to buy the exact 4x Amscope objective from the exact seller to make sure it is the good one...
In fact, my starting point was Robert Otoole's report. Unfortunately, for some time Amscope has stopped listing that 4X objective, and instead, is listing another model (??), which differs in shape: the hood of the front lens is tapered. These two objectives did not perform the same in Otool's report. To add to my confusion, Otoole's report was about a macrophotography gear, not a microscope (maybe only subtle difference, I am not sure). Furthermore, other microscopists mention significant quality fluctuations within a set of the same identical objectives. And I am aware of Apochronaut's comments about the Chinese 4X objectives, and the lack of detailed information from the manufacturer of the unbranded objective (this is an attractive paradox by itself). So, I rounded it all up and purchased a "generic" or "unbranded" objective of the same external shape. It represents all objectives that look like this.
zzffnn wrote:... Also note that Robert OToole used it without eyepiece (direct projection onto sensor). ...
This is another reason for me to keep the 4X objective and, with time give it a chance in direct projection.
zzffnn wrote:...LOMO 3.7x likely won't work for you either, as it has very long working distance and is not parfocal with other LOMOs. I would think its parfocal distance is a bit longer than 45mm as well, but am too busy to test it now. Do you want me to test it for you next Tuesday or so?
I am in no hurry, since I intend to keep the objective anyway. If you can, at leisure, test the LOMO 3.7X on a Zeiss standard system, and tell about its aberration compatibility and parfocality with DIN objectives, it will be very helpful and greatly appreciated.
PeteM wrote:... For the price, the import 4x seems OK; especially for sorting and scanning slides...
Hence I will keep it. It would be foolish of me to try and resell it - ordinary shipping costs alone are higher than the price of a new one of the kind.
I admire Olympus SPlans, sadly they produce too much CA with a Zeiss eyepiece.
75RR wrote:...
ImperatorRex wrote:...
Scarodactyl wrote:...
Thanks for mentioning the Zeiss 4X Planapo, which I forgot, and the Zeiss 1.6-5X; their disadvantage, however, besides the cost, is the shallow WD. The zoom is said to have WD=1.5mm at 5X, so I am guessing that it will not be much over 3-4mm at 4X, too risky to buy.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#12 Post by MicroBob » Sun Jul 14, 2019 1:34 pm

Hi Doron,
thank you for this interesting test! There are probably quite a few people who miss an objective in this range and would have been interested if the test result were better.
The Lomo objectives I know are ca. 33mm and almost parfocal to Zeiss Jena old. The 3,7:1 would have to be used with non-correcting eyepieces, contrary to the high magnifications that would fit your Zeiss West photo eyepiece.

A mismatch of objective and eyepiece would result in yellow and purple fringes at the border. This error should be largely removed by choosing just on colour channel. So there has to be an other error that causes the lack of sharpness at the border.

Perhaps a Leitz EF 4/0,12 might be interesting: Parfocal at 45mm, big working distance and plenty and cheap. I have one but I havent tested it in detail. My general impression was, that it is quite good. EF means "Extended Field" so semi-plan.

Bob

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#13 Post by zzffnn » Sun Jul 14, 2019 2:17 pm

I agree with MicroBob.

Objectives with around 4x power can be roughly divided into two categories (though optical compensation and reality is more complex than that):

1) those that are almost self-corrected and need minimal compensation from eyepieces; and

2) those that have abberations added, so that they can use the compensating eyepieces ideally designed for high power objectives.

I would also guess that the LOMO 3.7x and the Amscope 4x fall into category 1). Simple Huygenian eyepieces (that provide minimal optical correction) may be better match for those objectives.

Many modern low power objectives from big name brands belong to category 2). Noticeable exceptions are the Nikon CFN and CFI objectives.

Hobbyst46,

I don't have a Zeiss scope, though my LOMO K10x (compensating) wide field eyepieces were said to be optically similar to Zeiss Kpl10x. I would need to dig around to see if I have non-compensating eyepieces. I have not used the LOMO 3.7x much, as I usually start with my 10x NA 0.3 on my compound scope. I do remember Robert OToole (who tested my exact 3.7x on his camera system using direct projection) said that it is clearly not a "plan" objective, though it is critical for focus stacking.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#14 Post by MichaelG. » Sun Jul 14, 2019 3:38 pm

This [quoted verbatim from a vintage Zeiss publication, but with some 'word-wrap' hyphenation removed] confirms the point about objectives being 'deliberately' formulated to need eyepiece correction:
A lens error which has a very important influence on the satisfactory imaging of a visual field of a certain extension is the chromatic difference of magnification. Ever since Abbe's time, this error has generally not been corrected in the objective but by means of an eyepiece having an error of identical magnitude but opposite direction. Such eyepieces are called compensating eyepieces. ln order that a single series of eyepieces may be sufficient -- a fact which is today considered indispensable in the interests of easy operation of the microscope by less experienced personnel -- all our objectives have the same lateral chromatic aberration. The fact that this is the case with all our objectives ensures that the user of our microscopes need not bother about which type of eyepiece to use for a certain objective. Any of our eyepieces will do. However, our objectives should never be combined with eyepieces of another make if a more or less serious loss of image quality is to be avoided.
MichaelG.
.
Ref. 'Zeiss Optical Systems for the Microscope' (pp24-25)
http://www.science-info.net/docs/zeiss/ ... ystems.pdf
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#15 Post by Hobbyst46 » Sun Jul 14, 2019 6:31 pm

Thanks Bob, zzffnn and MichaelG.

My aim was to try and get an inxepensive 4X lens that can be merged into the existing setup. I knew I was taking a risk with the Chinese Plan objective. Perhaps in the future I will switch to direct projection, and then try the Chinese objective again, and see if, in the absence of "interfering" corrections from an eyepiece, it yields planar and CA-free images.
MicroBob wrote:Perhaps a Leitz EF 4/0,12 might be interesting: Parfocal at 45mm, big working distance and plenty and cheap. I have one but I havent tested it in detail. My general impression was, that it is quite good. EF means "Extended Field" so semi-plan.
Unfortunately, the Leitz EF 4 objectives I have seen on eBay so far are too expensive. I will keep on looking, yet would really like to be sure that Leitz fits. In retrospect, some folks have combined Leitz Periplan eyepiece with Zeiss Standard and apparently obtained nice images. The Leitz now seems to be a better candidate than the LOMO, which is not cheap either.
zzffnn wrote:...
In view of Bob's opinion and yours, I would postpone the LOMO test, for the time being. Many thanks for offering.

Hopefully I will test 1-2 other 4X objectives, just for fun.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#16 Post by PeteM » Sun Jul 14, 2019 7:07 pm

I did another quick test of my sample of Hobbyist's 4x plan achro, this time versus a 4x Olympus DPlan and using both Nikon CFWN 10x eyepieces (no corrections) and Olympus WHK 10x /20 eyepieces native to my stand. Goal was to see if the orange chroma tint at the field margins was caused by Olympus eyepiece corrections.

Seems not, in a quick visual comparison. The cheap 4x actually holds up pretty well in terms of a flat and accurate image versus the DPlan, but while the DPlan has only the slightest bit of color at the margins, the generic 4x shows a larger fuzzy ring with either set of eyepieces.

The tint might still be from corrections in the Olympus finite head. My own guess is that the generic 4x objective just isn't that great at the margins.

It still seems a bargain for quick scanning of slides, reasonably plan and sharp. And I wouldn't be surprised if photos taken through the central 70% or so would be OK. I wouldn't hesitate to buy it for a finder objective for someone whose detailed examination or photos would be at a higher magnification.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#17 Post by MicroBob » Sun Jul 14, 2019 7:35 pm

The Leitz EF objectives were basic choice fot Leitz microscopes in the early 1980s or so. Nothing especially expensive when new and not sought after, so when someone demands a lot of money today, this is unreasonable.
They were 45/160/10 design and intended for use with correction eyepieces with slightly less correction than Zeiss West and slightly more than Olympus.
I can make a comparison in the future, but this will take some time. I'm about to finish the work on my room but then there is a lot to do on the microscopy side, refurbishing Zeiss old DIC components among other things :D

Bob

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#18 Post by Hobbyst46 » Sun Jul 14, 2019 7:40 pm

PeteM wrote:I did another quick test of my sample of Hobbyist's 4x plan achro, this time versus a 4x Olympus DPlan and using both Nikon CFWN 10x eyepieces (no corrections) and Olympus WHK 10x /20 eyepieces native to my stand. Goal was to see if the orange chroma tint at the field margins was caused by Olympus eyepiece corrections.

Seems not, in a quick visual comparison. The cheap 4x actually holds up pretty well in terms of a flat and accurate image versus the DPlan, but while the DPlan has only the slightest bit of color at the margins, the generic 4x shows a larger fuzzy ring with either set of eyepieces.

The tint might still be from corrections in the Olympus finite head. My own guess is that the generic 4x objective just isn't that great at the margins.

It still seems a bargain for quick scanning of slides, reasonably plan and sharp. And I wouldn't be surprised if photos taken through the central 70% or so would be OK. I wouldn't hesitate to buy it for a finder objective for someone whose detailed examination or photos would be at a higher magnification.
Pete, this is interesting, and I am trying to understand the detail: your test included a matrix of 4 combinations:
a) unbranded 4X - Nikon CFWN
b) unbranded 4X - Olympus WHK
c) Olympus DPlan - Nikon CFWN
d) Olympus DPlan - Olympus WHK
Could they be graded ? a score of (I) FOV flatness, and (II) CA, for each ?

Side note: does anyone remember a similarly objective (pun) test of unbranded Plan (or even non-Plan) objectives, on a microscope for which they are designed, including eyepieces ? I mean, not a direct projection onto a USB eyepiece camera, but afocal with a DSLR camera ? using a ruler or stage micrometer or some other standard specimen, not a colorful slide ?
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#19 Post by Hobbyst46 » Sun Jul 14, 2019 7:48 pm

MicroBob wrote:The Leitz EF objectives...were 45/160/10 design and intended for use with correction eyepieces with slightly less correction than Zeiss West and slightly more than Olympus.
I can make a comparison in the future, but this will take some time....
Thanks Bob, I sure can wait.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#20 Post by MichaelG. » Sun Jul 14, 2019 7:51 pm

I have been digging through my old photos, and found this test image from 2010 which I took with the Zeiss PlanApo 4x on a bellows.
https://www.dropbox.com/sh/1kj7mym9ayh9 ... _qVRa?dl=0

The subject is a short length of IKEA paper tape-measure, white, with 1mm divisions.
Micro 4/3 sensor and underexposed.

There is some curvature of field [probably because the 'tube length'was not quite 160mm], but the important thing is that it shows the Chromatic Difference of Magnification [lateral chromatic aberration] rather nicely.

I suspect that a similar test using the 'unbranded' 4x might show less CDM, thus demonstrating that the corrections provided by a Zeiss eyepiece are incompatible with it.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#21 Post by PeteM » Sun Jul 14, 2019 9:13 pm

Hobbyst46 wrote:
PeteM wrote: . . . Could they be graded ? a score of (I) FOV flatness, and (II) CA, for each ? . . .
Yes, those were the combinations. This wasn't an exacting test - just looking at a bit of fern tip cells across the entire 4x field of view.

The 4x DPlan was the better lens with either Olympus or Nikon chrome free eyepieces (with only the SPlan better). Flat field and just a thin line of chromatic aberration at the edge.

The generic 4x was almost as good in flatness but with a wider fuzzy edge of chromatic aberration at the field margins. It got a bit better when I closed the field iris down, but never as good as the DPlan similarly closed down. The significantly more aberration showed up with both the Olympus and Nikon eyepieces, so I don't think a swap to neutral eyepieces is going to fix that. It could still be that direct imaging to a camera (no compensating Olympus optics intervening in the head) might have it do a bit better; but I'd suspect it will still be fairly decent toward the center but still inferior in terms of chromatic aberration at the margins.

Again, this was just a visual impression; which often looks better than a camera might see. That said, the cheap plan achro 4x seemed reasonably plan (cell membranes in focus edge to edge), with a decent image (not far off being as sharp and contrasty as the DPlan), but significantly more of an red-orange halo at the margins.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#22 Post by Hobbyst46 » Mon Jul 15, 2019 3:47 pm

Here is another reference, a Nikon 4X0.1 160/- Plan for comparison under identical conditions as above: afocal setup, Zeiss KPL 8X eyepiece, no condenser.
My impression is that the Nikon is better than the unbranded 4X from the aspects of flatness of FOV and CA, and much better with respect to vignetting.
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Nikon 4X0.1 Plan.JPG
Nikon 4X0.1 Plan.JPG (100.09 KiB) Viewed 1327 times
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#23 Post by MichaelG. » Mon Jul 15, 2019 4:44 pm

I think it is again evident that the Zeiss eyepiece is ''over-compensating"
Note that you have Yellow fringes in the position that my 'macro' shot with the Zeiss objective [and no eyepiece] has Blue.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#24 Post by Hobbyst46 » Mon Jul 15, 2019 4:47 pm

MichaelG. wrote:I think it is again evident that the Zeiss eyepiece is ''over-compensating"
Note that you have Yellow fringes in the position that my 'macro' shot with the Zeiss objective [and no eyepiece] has Blue.

MichaelG.
Yes. Later this evening I will post some images on the same stand, without any aberration-corrections.
Last edited by Hobbyst46 on Mon Jul 15, 2019 9:02 pm, edited 1 time in total.
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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#25 Post by MichaelG. » Mon Jul 15, 2019 4:59 pm

Hobbyst46 wrote:Yes. Later this evening I will post some images on the same stand, without any compensation.
Thanks ... I will be very interested
I [perhaps we] really need to get-to-grips with the theory and practice of this subject.
... There is always too much guesswork involved in 'mix&match' solutions.

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Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#26 Post by Hobbyst46 » Mon Jul 15, 2019 8:09 pm

So, here is a different setup, sort of direct projection, on the stand without condenser. The camera is an (unbranded) USB eyepiece camera, fitted with an (unbranded) 0.5X reducing lens, installed on one of the bino tubes, without eyepiece of course. Besides the objectives to be compared, the only optical parts are the prisms in the head. I hope and trust that these prisms do not add any correction. The FOV caught by the camera is only about 57% of the FOV.

On this setup, the Zeiss 6.3X Plan objective shows CA (as expected), whereas the Nikon 4X Plan does fairly well IMO - flat FOV and no CA. The unbranded 4X Plan shows a fairly flat FOV, yet some CA (better than the Zeiss though), and again, the brightness of the FOV falls off in the corners.

I include in this comparison two 10X objectives, a Zeiss 10X0.30 Neofluar and an Olympus 10X0.30 SPlan. Both yield a flat field, the Zeiss shows CA (as expected) and the Olympus shows only weak CA. In agreement with PeteM's comment, the Olympus SPlan shows excellent performance. With both objectives, I see a hot spot in the center of the image, probably because of the condenser-less illumination.

Overall, the unbranded Chinese 4X Plan objective is more suitable for the projection setup than for afocal setup of aberration-correcting optics, but given the smaller FOV of the former, the advantage is not dramatic. My conclusion is that, at best, this objective can be used for visual quick survey of slides and specimens, as suggested by PeteM. This is a pity, given the nice WD of ~15mm of the Chinese 4X Plan, that facilitates top-of-stage illumination. :?

Note: in the files below, objectives are Zeiss unless otherwise stated.
Attachments
6.3X0.16 Plan.jpg
6.3X0.16 Plan.jpg (130.03 KiB) Viewed 1293 times
Nikon 4X0.1 Plan.jpg
Nikon 4X0.1 Plan.jpg (35.43 KiB) Viewed 1293 times
Unbranded 4X0.1 Plan.jpg
Unbranded 4X0.1 Plan.jpg (217.47 KiB) Viewed 1293 times
10X0.30 Neofluar.jpg
10X0.30 Neofluar.jpg (198.39 KiB) Viewed 1293 times
Olympus 10X0.30 SPlan.jpg
Olympus 10X0.30 SPlan.jpg (153.21 KiB) Viewed 1293 times
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MichaelG.
Posts: 1462
Joined: Mon Apr 10, 2017 8:24 am
Location: NorthWest England

Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#27 Post by MichaelG. » Mon Jul 15, 2019 8:30 pm

An excellent set of reference images ... Thanks for sharing them.

May I just ask: is that Nikon objective designated 'CF' ?
... and could you please post a photo of it, to aid identification.

MichaelG.
.
Edit: if it's like this one ... no photo needed
https://www.ebay.com/itm/Nikon-Plan-4X- ... 3076873547
Too many 'projects'

Hobbyst46
Posts: 2130
Joined: Mon Aug 21, 2017 9:02 pm

Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#28 Post by Hobbyst46 » Mon Jul 15, 2019 9:01 pm

MichaelG. wrote:An excellent set of reference images ... Thanks for sharing them.

May I just ask: is that Nikon objective designated 'CF' ?
... and could you please post a photo of it, to aid identification.

MichaelG.
.
Edit: if it's like this one ... no photo needed
https://www.ebay.com/itm/Nikon-Plan-4X- ... 3076873547
Thanks Michael, the Nikon objective is not a CF... it is the same as in the eBay link.
Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo

MichaelG.
Posts: 1462
Joined: Mon Apr 10, 2017 8:24 am
Location: NorthWest England

Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#29 Post by MichaelG. » Mon Jul 15, 2019 9:15 pm

Hobbyst46 wrote:.. the Nikon objective is not a CF... it is the same as in the eBay link.
Thanks for the clarification ... This is clear evidence [if any were needed] that low power objectives are relatively easy to 'fully correct' and that Zeiss did deliberately adjust its version to match the family characteristic.

MichaelG.
Too many 'projects'

viktor j nilsson
Posts: 72
Joined: Thu Aug 23, 2018 10:12 pm

Re: Unbranded NEW 4X Planachromate objective on a Zeiss Standard microscope

#30 Post by viktor j nilsson » Mon Jul 15, 2019 9:31 pm

Hobbyst46 wrote:
MichaelG. wrote:An excellent set of reference images ... Thanks for sharing them.

May I just ask: is that Nikon objective designated 'CF' ?
... and could you please post a photo of it, to aid identification.

MichaelG.
.
Edit: if it's like this one ... no photo needed
https://www.ebay.com/itm/Nikon-Plan-4X- ... 3076873547
Thanks Michael, the Nikon objective is not a CF... it is the same as in the eBay link.
I feel fairly confident that this objective is from the CF line of objectives, that were made from the late 70's to mid-80's. Early CF objectives were mostly straight and unadorned. Some of the low-magnification objectives had this black style. Towards the end of the 80's, the CF line was updated and became the CF N line (N as in New). At that point, a knurled ring was added, with three bands divided into squares.


http://www.krebsmicro.com/Nikon_CF.pdf


Above is a link to a Nikon CF N catalogue posted by Charles Krebs, which is from 1989. Here, you can see that some of the black objectives are still listed as CF and are straight and simple (for example the CF plan achromat 2x), whereas others have been updated and given knurled rings (for example the CF N plan achromat 4x). I guess they didn't overhaul all optical designs overnight.

Based on this, i would call the black objective in the eBay ad a CF plan achromat 4x.
I'd expect it to perform quite well when used in a proper direct projection setup with no intervening optics.

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