Difference between FK and NFK eyepieces

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wilash
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Difference between FK and NFK eyepieces

Post by wilash »

Does anyone know the difference between the Olympus FK and NFK photo eyepieces? I know the NFK is the latter version, but is there a significant difference in quality between them?
Will

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twebster
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Post by twebster »

Hi ya' Will :D

The Olympus FK series of projection eyepieces were designed for 37mm parfocal objective lenses. These were Olympus' older objectives. The Olympus NFK series of projection eyepieces are designed to be used with the newer 45mm parfocal objective lenses.

Best regards, :D
Tom Webster
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wilash
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Post by wilash »

Tom, thank you. How do I know which is which? I have four lenses that are silver with a larger black top that are simply marked MPlan 20N, etc. And a newer one that is a D Plan 4. I believe the D Plan 4 would use an NFK.

What would the problem be if I used the wrong Photo Eyepiece with the wrong objective?
Will

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twebster
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Post by twebster »

Hi ya' Will :D

I'm not an expert on Olympus objectives but I think the M Plan objectives are for use with a metalurgical microscope. These objectives are corrected for use without coverslips and are designed for observing opaque specimens using external lighting. I don't know how they will perform using transmitted light.

The D Plan series of objectives are standard achromatic objective lenses that can be used with or without coverslips and are used with standard transmitted illumination systems.

To determine whether an objective is 45mm parfocal length or some other parfocal length simply focus the objective on a specimen and measure the distance from the base of the objective (where it screws into the nosepiece) to the specimen. That distance will be the parfocal length. DIN standard is 45mm.

I don't know what the differences will be if you mix NFK projection eyepieces with FK projection eyepieces. I bought FK projection eyepieces because the LOMO objectives I have are 33mm parfocal. My "new" Zeiss objectives are 45mm parfocal. When I get my new digital camera set up I'll shoot some test exposures to see if there's any problems using the FK projection lenses with 45mm parfocal objectives.

Best regards, :D
Tom Webster
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wilash
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Post by wilash »

Tom, thank you for your answer. Another piece of the puzzle falls into place. Now I know how the parfocal distance is measured.

Maybe I should back up here and explain why I am asking this question. I resently bought an Olympus Vanox Universal Research microscope - not the latest box-like Vanox, but the one released in the 70's that looks like the BH-2 on steroids. It is setup for episcopic DIC. It came with four MPlan objectives, which as you pointed out, is what it should have. The microscope was also equipt with a 4x5 camera. When I got it, I found there was no photo eyepiece between the frame and camera which meant it was not going to take anything but small round pictures.

A catalog that was supplied with the microscope showed that an NFK eyepiece was necessary, but, from your first answer, I also noticed that the objectives in the catalog were the D Plan and S Plan and not the objectives that came with the scope. I had noticed there are FK and NFK eyepieces. Since this new area of microscope optics is new to me, I thought I had better not make the assumption that the difference between FK and NFK optics were cosmetic and post a question here.

The D Plan 4 I picked up on a strange piece of hardware from an optical bench used for inspecting aerial images. The MPlan 5 I recieved with my scope has a small chip on the front element and I thought I may use the D Plan instead of the MPlan 5. It seems compatible with the MPlan 5 Normaski prism, at least with a visual inspection, as well as having a slightly brighter and higher contrast image.

I know the Vanox has a 160mm tube length, so infinity optics are a no-no. But what other limits to my choice of optics do I have. I would like to get some photo eyepieces, but how important are the FK and NFK designations? NFK seem to be more common in auctions and Olympus still have them in stock (production was stopped 12 years ago).

Well , that is the story. I am tying to nurse my Vanox into shape. The photo eyepiece is one small piece of this puzzle I need to solve.
Will

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piotr
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Post by piotr »

Hi Will,

Congratulations on the Vanox! :-) It must be a wonderful microscope. Could you post a picture of it?
Piotr

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wilash
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Post by wilash »

Piotr, this is it:

Image

It is uglier in person. It is a pale green - not the original color. Someone (not me) had painted it for one reason or the other. They did a good job accept they put the fine focus knob on the wrong side when they assembled it. Like I said above, it is setup for episcopic DIC. I have had to tweek it here and there, but is was in working condition, although beat up. I picked up the scope / fiber-optic illuminator set on ebay. It was the DIC that won my heart. :P

I just recieved an FK photo eyepiece and shot some film tonight. Japan is in Golden Week so I am going to have to wait a bit before I get it back. I hope to try the FK / D Plan combination tomorrow - visually there seems to be no problem in the focusing telescope.
Will

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Post by Guest »

Will, it's a beautiful microscope! How does the fiber optic illuminator peform? Is its intensity enough for DIC work? Let us know about photographic results.

Piotr

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