Olympus vs Nikon CF?

[bklein]

Ok, so lots of support for Nikon CF objectives for our use but how do the various Olympus objectives compare? Is there an Olympus series that we should watch for?

[ChrisR]

A common question, which you'll find a lot about if you search, particularly for Charles Krebs' comprehensive posts on the subject.
Nikon were unusual in doing all the Chromatic Aberration control in the CF objectives, without leaving any for correction in a tube lens or eyepiece. There seem to be one or two other manufacturers now, but they're for "infinity" systems.
If you want to use a microscope objective on a camera, you need one for a "finite" tube length, which will be 160 or 210 mm.
Unfotunately many of the NIkon CF lenses weren't marked as such, just to be annoying, but a 10x NA 0.25 or 0.3, or a 10x Mplan, would be a very good start.

[bklein]

I just got a chance to try (on a Olympus microscope) out the objectives I just got off ebay that supposedly were faulty with "oil seep". Some are infinity, some are finite.
All seemed to display an image with not too much difference. The subject was an IC die. Is it a totally different world though with a bellows - where a finite looks good but an infinite looks really bad? I haven't seen image examples of this...
Sorry to ask so many questions under one topic but one was a Nikon 10X E Plan .25 160/-. What's with that - how does it compare to a CF? (I have yet to get the RMS adapter stuff in so I can try on a bellows).

[ChrisR]

Depends on the microscope - a straight CH or BH doesn't have a tube lens out of the box, until you add a trinicolar with down-the-tube lighting, as far as I'm aware - (which isn't a long way).
A Nikon E objective IS a CF, just an Economy version. Maybe it's field isn't quite as flat, maybe no big deal, especially if you're stacking.
Comparing two otherwise identical 10x objectives, if the 160 is 10 out of 10, the infinity one comes about 7 I'd say. That's a much bigger difference than a drop in NA from 0.3 to 0.25.

Be careful with IC dies, I find them rather an odd subject.

RMS adapter stuff

Make a hole in a body cap, or even dark card.


Check http://photomacrography.net/forum/viewtopic.php?t=7705 and the links in that.
Charles put the CF finite brochure here http://www.krebsmicro.com/Nikon_CF.pdf

[mgoodm3]

All of the olympus non-infinity objectives that I have used, s-plan, have quite a lot of chromatic aberration when used on a bellows and not A particularly flat field. I presume that means that they do some corrections in the eyepiece.

[Charles Krebs]

Chris has got this down perfectly!

An additional thought or two...
You will certainly be able to get an image with an "infinity" objective on a bellows without the tube lens. The question is how good will it be? You are using the objective in a manner not intended. Personally I have tried it a couple of times (I think Chris may have done it more). The results ranged from really horrible to "pretty good". I suspect here is a huge variation in end results. It would certainly depend on what, if any, final corrections were designed into the proper tube lens, and could very well be sensitive to the objectives NA and extension used.

The thing about Olympus "finite" objectives (among others) is that they were all designed to be used with chromatically corrective eyepieces (as were some of their earlier M type infinity objectives). When I tried my 4X S Plan Apo on a bellows I found the uncorrected chromatic aberration too strong. Again, this is not a "defect" it was simply the nearly universal way of designing microscope objectives. For their intended usage the designer knew there would always be an eyepiece of some type used, and it was utilized to complete the overall image formation.

If, by some chance you have some Nikon "infinity" objectives (or would like to venture into that realm) keep in mind that a Nikon tube lens is not all that expensive (about 1/3 the price of a Mitutoyo... don't know why). It should not be that hard or expensive to make a set-up using the tube lens.

When you get into large stacks, every image becomes a "production". There is a great deal of time spent preparing the subject and lighting, shooting the stack, computer time to run the stack, and then "clean-up" editing. You don't want to make more work for yourself dealing with optical image issues that result from misusing the objectives. Fortunately there are some very good and reasonably priced objectives that work great for this purpose.

(Olympus make a "pitch" for eyepiece compensation on page 5 of this objective brochure:
http://krebsmicro.com/olympus-OBJECTIVES_LB.pdf )

[rjlittlefield]

If, by some chance you have some Nikon "infinity" objectives (or would like to venture into that realm) keep in mind that a Nikon tube lens is not all that expensive (about 1/3 the price of a Mitutoyo... don't know why). It should not be that hard or expensive to make a set-up using the tube lens.

One source: Edmund Optics sells the Nikon tube lens as an "Accessory" for their CFI objectives. The tube lens is only $201, versus the objectives that are listed for example $825 for 10X and $1553 for 20X. The working distances for these objective are nice, 17.3 mm and 13.0 mm. The combination of a new tube lens and a used objective could be pretty attractive, albeit "some assembly required".

--Rik

[bklein]

Yeah, I haven't seen anyone kludge up a bellows system with a tube lens or eyepiece involved... I mean sure the microscope is best for this. But my microscope has a stereo head, not trinocular. I'd like to hear from anyone that has experimented with Olympus objectives with tube lens or eyepiece in the bellows assy.
The tube lens for Olympus seems to show on ebay fairly often for under $100. Trinocular head is like $500. uggh. Tube adapter... ugghhh.
PVC here we come.
My microscope has a vertical tube-mounted illuminator as well - metallurgical use (don't know the part number off the top of my head). It appears to have lenses in the light path too right?
Last thing, how would a tube lens differ from a "photo eyepiece" in such a bellows kludge?

Barry

[OzRay]

I'm in the process of seeing if one of the Chinese lens adapter makers might be interested in making a microscope objective adapter for bellows use. I've suggested that all that is really needed is a tube that has a C Mount thread on the camera/bellows mount side and an RMS thread on the lens side. By using a C Mount adapter, you can get just about any C Mount to 'Your Camera' adapter to suit, thus making it much simpler to make a universal adapter.

I guess the greater the interest, the more likely something like this can be achieved.

Cheers

Ray

[PauloM]

Ray,

Are you sure you didn't mean T adapter (M42x0.75)?
There already are such adapters on the market, but it sure would be nice if the Chinese would start selling them at "Chinese" prices!

[pierre]

Hi All,

I tought the "infinity" obectives need a photo eyepiece above the tube.
Is only a tube lens needed like I do with my "170/" objectives ?

Cheers

Pierre

[rjlittlefield]

The infinity objective plus a tube lens produces a real image that can be viewed through an eyepiece or projected directly onto a sensor if it is the right size (roughly 18-25 mm diameter, depending on the objective and tube lens).

If the sensor is not the right size, then the image must be made bigger or smaller with another lens, such as a photo eyepiece.

--Rik

[Charles Krebs]

Seems to be some confusion...

A finite objective creates a real image -- known as the "intermediate image" in microscopy -- in the eyepiece tubes (and trinocular tube if it is a trinocular head). The intermediate image plane is located about about 10mm below the tube edges. This intermediate image is formed by the objective alone, with no other optics in the "tubes". The viewing eyepieces are inserted into the tubes and receives this image (the eyepiece aperture is at the exact location of this real, intermediate image).

With an "infinity" objective used properly, there will be no real image formed directly by the objective. The light coming from the objective is focused to infinity. In order to form the real, intermediate image there is an additional optic called the tube lens (or "telan" lens) that is inside the microscope. This tube lens takes the "parallel" rays and forms the real, intermediate image in the eyepiece and trinocular tubes. You typically never see this tube lens. It is internal and fixed. It should not be confused with eyepieces or photo-eyepieces or projection eyepieces. You will almost never see a "tube lens" for sale as they are generally a fixed internal part of a microscope. (But certain ones are available from places like Edmund Optics).

So with both finite and infinity type microscopes, a real intermediate image is formed inside the eyepiece tubes, about 10mm below the edge. The finite objective does it directly, with no intervening optics. An infinity objective needs an additional lens (the tube lens) to form this real image.

Once you have this real, intermediate image created you can do different things with it. Viewing eyepieces will pick it up for visual observation. A projection type eyepiece can be used in the trinocular tube to project the image onto a camera sensor. If you could get a a sensor inside the eyepiece tube (about 10mm down) you could place this intermediate image directly onto the sensor. This is, in effect what we are doing when we put a finite objective on camera bellows. We are positioning the camera sensor at the location where the objective forms the real ("intermediate") image.

But note that the infinity objective should really have a tube lens to create a good real image. (Yes... you can get an image to form without a tube lens by "upsetting" the design parameters, but it's quality is questionable). So if an infinity objective were to be used on a camera bellows, you really should have the proper tube lens positioned at the proper location between the objective and the camera sensor.

And while we can get an image directly from a finite objective, we must always consider if the objective was meant to be used with eyepieces that corrected for significant chromatic (and other) aberrations. This is why, for direct use on a camera bellows, the Nikon CF finite objectives are such a nice choice. Being finite, they do not need a tube lens. They also were designed so that all chromatic corrections were accomplished in the objective itself.

[NikonUser]

Charles wrote
"If you could get a a sensor inside the eyepiece tube (about 10mm down) you
could place this intermediate image directly onto the sensor. This is,
in effect what we are doing when we put a finite objective on camera bellows.
We are positioning the camera sensor at the location where the objective forms
the real ("intermediate") image."

OK, but why would you place the camera sensor 10mm down? A microscope eyepiece has another lens at its top (10mm above the lower lens) and the human eye has another lens and then its sensor another 10 mm or more back from this lens.

With a 160mm tube length, the final image seems to me to be formed at about 170mm, or further, from the object and not at the 150mm you suggest.

I'm just trying to understand all this.

[Charles Krebs]

NU,

The aperture of the eyepiece is at the plane of the intermediate image (doesn't really matter where the eyepiece's top lens, or "eye lens", is). In a microscope the intermediate image is always down from the edge of the eyepiece tube some distance. Historically it varied from manufacturer to manufacturer, but at some point a DIN standard (#58887) was adopted that made it 10mm down from the tube edge. The eyepiece then forms a "virtual" image (an enlarged image that appears to the human eye to be at 250mm distance). This virtual image then requires another lens to form a real image... the lens in your eye serves this purpose by creating a real image on the retina. The pupil of the eye is placed above the eyepiece to coincide with the eyepoint of the eyepiece.
From an Olympus web page:
Light rays emanating from the eyepiece intersect at the exit pupil or eyepoint, often referred to as the Ramsden disc, where the pupil of the microscopists eye should be placed in order for her to see the entire field of view (usually 8-10 mm from the eye lens).

If you could actually place your eye's pupil at the exact position of the microscopes intermediate image you would not see any image, just light.

So in reality, a 160mm tube length objective forms the image at 150mm from the objectives shoulder. Sometimes you will see it written as 160mm mechanical tube length, which is, I suppose, more accurate.

Here's a useful reference:
http://www.olympusmicro.com/primer/anat ... ation.html

Also read this old Leica memo, about half way through (section about 160mm mechanical tube length):
http://science-info.net/docs/leitz/Leitz-160mm-Memo.pdf