Nikon condenser question

[PNWmossnerd]

Hi all,
I have a Nikon Labophot and would like to upgrade the stock abbe condensor with something this is achromat since I require high quality color photographs for my research (I am a PhD student studying mosses).

Presently, I am thinking of buying the .90 NA swing top achromat condenser for the labophot. However, I frequently use the 1.25 NA100x plan apo oil objective. Since the NA of the swing top condenser is less than the NA of the objective, I worry that images taken using the 100x objective may not look great. At the moment, I use the oil objective with oil between the slide and the objective, but not between the condenser and slide. My understanding is that this practice limits the NA of the condenser to <1.0 anyway, meaning that there may not be a significant NA different between the abbe condenser as I currently use it and the swing top achromat.

Do any forum members use this condenser with a 100x oil objective? If you do, how is the image quality?

I also see a 1.4 NA achr-apl objective designed for the Nikon Eclipse series microscopes. Does this condenser fit the Labophot dovetail, and if so, would it produce a good image on the Labophot?

Thanks to everyone for helping with my condenser confusion!

[apochronaut]

This question comes up a lot.

.90 achromat condensers, while convenient, do impose some limitation on a higher N.A. immersion objective. This is one of the reasons that some manufacturers from the later 20th century on, limited their lower power immersion objectives to an N.A. of 1.0. Earlier on , it was more common to see 3 or 4mm objectives with N.A.'s up to 1.4. The expectation was that they would be used with an immersed high N.A, condenser.

My personal opinion is that, if you are photographing, and using an objective of 1.10 or higher, I would only replace an abbe 1.25 oil condenser with a .90 achromat/aplanat. If you already have an abbe aspheric 1.25 oil, there is little to be gained in replacing it with a dry achromat.
Aspherics are way better than a plain abbe and the complete edge correction plus the possibility of an N.A. matching that of your objective, overcomes any major differences between it and a dry achromat. The asheric lens, makes them function very much like an achromat. If the condenser you have in mind was a higher N.A. oil achromat, then I could see the benefit but not a dry one with an N.A. under 1.0.

The resulting N.A. of a 1.25 oil immersion objective when used with a .90 condenser is about 1.12 +-.

[zzffnn]

Upgrade your objectives to apochromatic ones first, if you have not. You will see more improvement that way. They don't have to be plan apo, depending on your application.

I have DIY'ed many 3rd party brand condensers to my Optiphot. You can use super glue, Legos, wood blocks, washers, camera lens adapters, ect.

[PNWmossnerd]

Thanks to both of you for your thoughtful replies. At the moment, I am fortunate to have all plan apo objectives (4x, 10x, 40x, and 100x oil immersion).

It sounds like I should spring for the 1.4 achro apl condenser if I want to upgrade this microscope.

Does anyone on the forum have experience with this particular condenser/stand combination?

[zzffnn]

My short LOMO apos are not plan. But I did modify my Nikon Optiphot and Labophot to use short objectives and Olympus 1.4 achro apl condenser.

I like to use extreme oblique and darkfield sometimes, so 0.9 achro apl is not enough for me (I always oil objectives AND condenser). Though for plain brightfield 0.9 condenser may be enough.

I did compare my 1.4 achro apl to my other (what appears to be) 3-element 1.4 condenser without marking (of apl or achr) and found it to be slightly better. Surely worth the $50 I paid for it. Maybe even worth $100. Not sure if I will pay $150 for that improvement. Definitely not paying $200 from my wallet. But your mileage may vary.

[apochronaut]

Obviously, it is unlikely that the condenser/objective combination designed in the factory can be bettered by a D.I.Y., so your decision to look for a Nikon 1.4 N.A. achromat aplanat does make sense, if you are wanting to get the best possible performance out of your plan apos. However, I echo Fan's remarks regarding the mixing and matching of condenser objective combinations, in that any 1.4 N.A. achromat aplanat condenser would be a hair's breadth of the performance of any other and so an actual Nikon condenser is probably not necessary, if you find another for a price you cannot refuse. Be careful though, that it also circumscribes a sufficient corrected circle in order to meet your objective's design parameters. Beware of condensers that you are not sure are in fact achromat or aplanat. Many 1.4 N.A. condensers are not.
The area circumscribed by the condenser is an overlooked specification. If you are using objectives that have a very wide field of plan performance, a condenser which otherwise is spec'd at 1.4 , achromatic and aplanatic could conceivably fall short of providing that specification to the full circle of the objective. This is less likely when fitting a modern condenser to older objectives, than the other way around. Generally, the wider the actual lenses are in the condenser, the wider is the circle in which they will meet specification. All lenses have distortion and aberration but the wider the lens diameter, the wider the area that limits those defects. This is why aspheric abbe condensers are so superior to abbe condensers because the peripheral area of ca is very small for the aspheric and very large for the abbe. Aplanats, use a combination lens system to effect edge correction but the arbiter of the corrected circle is still greatly controlled by the diameter of the lenses themselves.

[zzffnn]

PNWmossnerd,

I forgot to mention that I am indeed using a wide modern (1980 ish) Olympus 1.4 achr apl condenser with older (1960 ish or older) objectives with narrow field of view (at around 18mm). The condenser seller had multiple ones for me at the time and I purposely picked the one with wide top lens (so that it would be a safer choice for providing the objectives).

And I DIY / mismatch parts for hobby use. So to get best possible professional results, you will surely be safer with objectives/condensers of the same brand and design.

[PNWmossnerd]

Thanks again for your detailed replies. While I am an experienced microscope user, I haven't given much thought to the equipment I use until recently, so I hope that my questions don't come across as too pedantic. It sounds like using a Nikon 1.4 achro apl condenser would give me the best possible results.

However, after reading your responses I have managed to find several Olympus 1.4 achro apl condensers designed for the BH-2 series scopes for much cheaper than I can find the equivalent Nikon condensers. Based on your reply, zzffn, you appear to use this condenser with a Labophot. What modifications were necessary to make this condenser play nice with a Labophot stand?

My understanding is that the condenser dovetail on the BH-2 is similar enough to that of the Labophot that they are interchangeable. Did you find this to be the case?

[zzffnn]

PNWmossnerd,

Yes, BH2 and Labophot have similar sized condenser dovetails, with one being slightly larger. I cannot remember which is larger though. I will try to search the forums for you.

My adaptation is likely not applicable to yours, because I needed to raise up condenser 12mm for my short 33mm objectives. So I glued some Lego risers onto the Olympus condenser, then glued those Legos to a Nikon dovetail condenser (sold to me by a Nikon dealer for $30 or $40, without adding shipping cost).

I can measure original height and dovetail size of my Olympus condenser for you, if relevant parts are accessible (and not blocked by my modification).

You need to make sure the following is about the same between the two condensers: height, top lens dimension and dovetail diameter.

[zzffnn]

My Olympus condenser looks like this one:
http://earth2geologists.net/Microscopes ... denser.JPG
http://earth2geologists.net/Microscopes ... Scopes.htm
http://www.used-microscope.org/product/html/?114.html

Its top lens diameter is 16.5 mm, height is 50 mm and bottom dovetail diameter is around 60mm. Dovetail diameter may not be accurate as it has been blocked by my modification (which I do not want to destroy, because it took me quite some time to align everything perfectly optically and glued them down).

Member Lorez said before that Nikon Labophot 2 condenser can fit on Olympus BH2, but BH2 condenser cannot fit on L2. He did not seem 100% positive though. So you may want to double check somehow.
viewtopic.php?f=5&t=2806&p=24339&hilit= ... ail#p24339

[zzffnn]

Lorez is likely right. See confirmation here (that Olympus may use a slightly larger dovetail):

http://www.photomacrography.net/forum/v ... r+dovetail

Such adaptation may be difficult to do by hand (without a lathe). You need to reduce diameter of the Olympus condenser evenly. It is possible to grind it down with hand tools, but it may take you an hour or two.

[zzffnn]

There may be other ways to grind down a similar condenser. You may want to ask that question as a separate thread. We have some good machinists and DIYers in this forum, I believe.

[PeteM]

. . . My understanding is that the condenser dovetail on the BH-2 is similar enough to that of the Labophot that they are interchangeable. Did you find this to be the case?

Not quite. The good news is that the optical match isn't bad.

As others do, I'll swap things around -- and keep a table of condenser measurements. My Nikon Abbe, achromat, and phase condensers are around 45.5mm max diameter at the dovetail and have about 70 degrees taper. My Olympus Abbe, achro, aplanat, darkfield, phase etc. are just under 47mm max diameter at the dovetail and have 60 degrees taper.

What this means is that you can fit a Nikon condenser in an Olympus stand, but not (at first) the other way around.

The easiest work around, for someone without a lathe to machine dovetails, is to get a spare condenser carrier for your Nikon (the little horse shoe shaped bit that pulls out once you unscrew the condenser fixing screw). That part will likely come from a trashed Labophot or Optiphot stand with bad plastic focus and condenser gears. Using something like a Dremel tool and a grinding burr, very carefully enlarge it to fit the Olympus dovetail.

You also need to check that a condenser lens top will reach through and to the top of the stage. There are some cases where it will be too large in diameter or too short in height. FWIW, stages are a reasonably good swap both ways. You may need a somewhat longer fixing screw.