Looking for Nikon CF Plan/Phase Short Barrel Objectives (FOUND)

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stitchy.mitch
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Looking for Nikon CF Plan/Phase Short Barrel Objectives (FOUND)

#1 Post by stitchy.mitch » Wed Feb 27, 2019 5:59 am

The matter of the microscope is mostly settled, but a set of objectives for phase contrast, or plan objectives is of interest. Anyone selling any, or knowing of a good source of any is welcome to comment.

~Mitchell
Last edited by stitchy.mitch on Thu Mar 14, 2019 2:35 am, edited 1 time in total.

photomicro
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#2 Post by photomicro » Wed Feb 27, 2019 10:19 am

stitchy.mitch wrote:The matter of the microscope is mostly settled, but a set of objectives for phase contrast, or plan objectives is of interest. Anyone selling any, or knowing of a good source of any is welcome to comment.

~Mitchell
I thought the short barrel Nikon objectives were *not* CF.

I have 'spare';

E Plan 40 Ph3
M Plan 40 210
Fluor 40/0.85

These are CF, but are DIN length.

PeteM
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#3 Post by PeteM » Wed Feb 27, 2019 4:41 pm

photomicro wrote:
stitchy.mitch wrote:The matter of the microscope is mostly settled, but a set of objectives for phase contrast, or plan objectives is of interest. Anyone selling any, or knowing of a good source of any is welcome to comment.

~Mitchell
I thought the short barrel Nikon objectives were *not* CF. . .
As you suggest, the Nikon short barrel objectives require correcting eyepieces -- and don't really mix very well with the later DIN standard length objectives.

stitchy.mitch
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#4 Post by stitchy.mitch » Wed Feb 27, 2019 7:43 pm

Admittedly the details about whether or not it would be better to have short-barrel objectives, or CF objectives or whether or not short barrel objectives can be CF objectives still eludes me.

I'm looking for objectives for a Nikon S-kt, which may make it much easier to realize what I am actually looking for.

ChrisR
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#5 Post by ChrisR » Wed Feb 27, 2019 8:53 pm

The Nikon -S is the black one, right?
...whose objectives had a black knurled ring around and need correction.

I have a bunch of later Nikon objectives - all chrome, and none need correction, afaik.

PeteM
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#6 Post by PeteM » Thu Feb 28, 2019 12:17 am

stitchy.mitch wrote:Admittedly the details about whether or not it would be better to have short-barrel objectives, or CF objectives or whether or not short barrel objectives can be CF objectives still eludes me.

I'm looking for objectives for a Nikon S-kt, which may make it much easier to realize what I am actually looking for.
Mitch,

First, some definitions. Various makers "short barrel" objectives were about 33-37mm long, measured from the face of the nosepiece to an in-focus specimen. "Long barrel" objectives were initially compliant to a DIN standard of 45mm measured the same way. A 100x objective (with a very tiny distance between it and the slide when focused) would be almost 45mm long. Currently, Nikon objectives are even longer -- 60mm.

I'd have to check to see if the Nikon S-Kt can even take 45mm long objectives. Could be there's just enough room; but not sure.

The older Nikons (along with most every other top maker) did some corrections for chromatic aberration (and often spherical aberration and field flatness) in the eyepieces. When all was said and done, you got a good image. Eyepieces that correct for a given maker and model are typically described with a "C" (compensating) or "K" (same thing) in the model. You want to get the right ones for Nikon S.

Later Nikons (also and eventually with many other makers) went to longer objectives and tried to handle more (or all, in the case of "chrome free") corrections with more lenses packed inside the approx. 10mm longer objective. Current Nikon objectives are now approx. 25mm longer than the short barrel objectives they and most others had. The extra glass gives wider fields, sometimes better corrections and correspondingly higher prices. The extra lens elements can reduce contrast, but more modern coatings give it back. In the case of the extra long (60mm) Nikon infinity objectives that are current production, they also give a bit more working distance.

For makers like Nikon and Olympus objectives came in a whole bunch of different price and quality levels. For example with Nikon's later objectives you might find:
- Achromats without a plan field - often marked "E" for educational
- Plan achromats - often marked E Plan
- Fluorities good for UV
- Plan fluorities or "semi apochromats"
- Plan apos (apochromats)

Prices go up almost exponentially as you move from educational level objectives to plan apochromats and more exotic lenses for water immersion, fluorescence, confocal etc. methods.

For your Nikon S-Kt you'll find the short barrel plan objectives for brightfield and their phase objectives provide very good images. About all you'll notice compared to objectives costing far more is a somewhat smaller field of view. You might even come across an apochromat at a reasonable price (say, $100 rather than the $600++ a single more modern one -- used -- might go for).

What you don't want to do is mix short barrel and long barrel objectives on the same nosepiece. First, because you'll have to keep wildly adjusting focus. Second, because you'll likely damage one or more objectives or slides in the process. Third, because you'll need to keep swapping eyepieces between Nikon compensating and Nikon neutral types.

Fourth reason, in your case, to go with the short barrel objectives designed for your scope is that the phase contrast ones will match up with the phase contrast condenser that fits that scope.

On edit - "compliant" not "complaint" to DIN
Last edited by PeteM on Thu Feb 28, 2019 7:17 am, edited 1 time in total.

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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#7 Post by zzffnn » Thu Feb 28, 2019 5:03 am

What PeteM said +

Many older microscopes that come with short barrel (33-34mm parfocal) objectives will take 45mm parfocal objectives.

At least the 3 "short barrel" scopes I had can use 45mm objectives (I only have LOMO now and have sold the other two):

Nikon S
AO series 4
LOMO Biolam

Most, if not all, original Nikon S (short) objectives are NOT CF. But you can probably buy a short Apo objective with a pair of K eyepieces for less than $100 USD shipped.

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75RR
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#8 Post by 75RR » Thu Feb 28, 2019 6:30 am

The older Nikons (along with most every other top maker) did some corrections for chromatic aberration (and often spherical aberration and field flatness) in the eyepieces. When all was said and done, you got a good image. Eyepieces that correct for a given maker and model are typically described with a "C" (compensating) or "K" (same thing) in the model. You want to get the right ones for Nikon S.
Agree, the need for compensating eyepieces was/is the rule rather than the exception. You should not see it as a big problem, it was designed that way and has a simple solution.

There is a quite large selection of objectives for the S-Kt according to the manual ... enough to keep anyone busy.

https://www.dropbox.com/s/ascxmzyvy2gix83/skt.pdf?dl=0

Note: No need to create an account to download from Dropbox.
Just scroll to the bottom of the invitation window and click on 'No thanks, continue to view'
Then press 'download' at top right of screen.
Zeiss Standard WL (somewhat fashion challenged) & Wild M8
Olympus E-P2 (Micro Four Thirds Camera)

abednego1995
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Re: Looking for Nikon CF Plan/Phase Short Barrel Objectives

#9 Post by abednego1995 » Thu Feb 28, 2019 6:56 am

Another small thing. (probably of the purist sort. and only a problem at extreme NA's above 1)

Nikon short barrel objectives have a parfocal distance of 33.6mm, and later CF, NCF (DIN standard) objectives have 45mm.
Both will admittedly fit on a S-Kt, however with the 45mm objectives at the expense of lower stage height.
The problem is, the condenser on the S-Kt will accordingly be 11.5mm lower than designed height, getting near the field lens.

Since the field lens projects the image of the illuminating filament on the condenser aperture, you will have to compensate for the lower condenser aperture height by shifting the bulb rearwards in the socket.
T̴h̴e̴ ̴S̴-̴K̴t̴ ̴h̴a̴s̴ ̴a̴ ̴b̴u̴l̴b̴ ̴s̴o̴c̴k̴e̴t̴ ̴t̴h̴a̴t̴ ̴i̴s̴ ̴f̴i̴x̴e̴d̴,̴ ̴s̴o̴ ̴I̴ ̴d̴o̴u̴b̴t̴ ̴t̴h̴a̴t̴ ̴t̴h̴i̴s̴ ̴i̴s̴ ̴p̴o̴s̴s̴i̴b̴l̴e̴ ̴(̴T̴h̴e̴ ̴S̴-̴K̴e̴,̴ ̴L̴-̴K̴e̴ ̴b̴a̴s̴e̴s̴ ̴h̴a̴v̴e̴ ̴a̴ ̴f̴r̴e̴e̴ ̴m̴o̴v̴i̴n̴g̴ ̴s̴o̴c̴k̴e̴t̴,̴ ̴s̴o̴ ̴t̴h̴i̴s̴ ̴i̴s̴ ̴"̴p̴o̴s̴s̴i̴b̴l̴e̴"̴ ̴)̴
EDIT1
Sorry, S-Kt provides adjustable bulb position.
EDIT1

However, shifting the bulb from the intended position relative to the illuminator collector will probably screw the aplanatic condition of the collector.(This will be a problem even for the S-Ke and L-Ke)
So when using more sophisticated condensers than the Abbe (Abbe condensors won't work properly at their maximum NA's anyway....) this will manifest as an inability to get a planar image of the filament in the back focal plane of the objective, losing full NA resolution.

In short, in a limited capacity 45mm parfocal objectives will work on a S-Kt. However for critical high NA work conjugate image planes in their proper positions are a must.
Ways to compensate for this would probably involve a shorter focal length field lens or physically elevating the whole arm setup 11.5mm relative to the illuminator base by inserting a thick shim.

Technically paranoid? Yes, probably.
What matters most, is that you get nice images from the scope.
Even if it doesn't adhere to theory, many people get nice images and they're happy!

EDIT2
Gosh, I didn't notice that the S-Kt has a diffusing filter in the base.... the Kt base only gives pseudo-Koehler in that sense. (see p.26 of the manual 75RR linked to us, Thanks!)
Please forget all the jargon above, it won't apply for a system that doesn't have proper Koehler (It still applies for the S-Ke and L-Ke).
The diffusing filter will even out the image of the filament over the field at the cost of light flux lost in scattering. This will make illumination alignment less critical.
Just check the back focal plane of the objective when doing high NA observation, if it's filled with light, you will probably be mostly happy.
So, yes 45mm parfocal objectives will work OK on the S-Kt. Just be sure to check the tube length (160mm, not 210 or inf.), and coverslip correction (usually have 0.17 engraved) for objectives that have NAs above 0.3.
EDIT2

Cheers,
John


P.S. If you're looking for phase systems for the S-Kt, CF/NCF objectives are a big no-no. There are no phase condensers with matching annuli for those that fit the condenser holder of the S-Kt.

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