How to find a tube lens for Nikon AZ Plan 5x/0.5 objective?

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Ichthyophthirius
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How to find a tube lens for Nikon AZ Plan 5x/0.5 objective?

Post by Ichthyophthirius »

Hi,

I got my hands on a Nikon AZ Plan Fluor 5x objective which is part of the Nikon Multizoom AZ100M microscope http://www.nikon.com/products/instrumen ... /index.htm

I only have the objective, not the rest of the microscope :wink:

I'm wondering if it is possible to mount this objective directly in front of a tube lens in order to take photos?

Nikon gives very little technical information on these.
- it's for infinite tube length
- NA 0.50, WD 15 mm
- tube lens is probably f=100mm from a snippet of information on the web

- I assume that the CA is corrected in the objective, as that is what Nikon usually does

The problem: the lens has an NA of 0.50, however, on the zoom microscope the NA is not achieved at a zoom factor of 1x. At that zoom factor, the NA will be around 0.10. Only by increasing the zoom setting to about 5x will the full NA of 0.50 become usable.

From what I've read on the Nikon website, at low zoom factors, the zoom optics effectively stop down the objective to a smaller NA.

Might it be possible to get around this by mounting a tube lens directly behind the AZ Plan objective and have the high NA available even at low magnification (in the 5x-10x range)? Maybe a Raynox DCR-150 (f=125mm) or a 135mm telephoto lens?

Kind regards, Ichthy

Image

g4lab
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Post by g4lab »

This is the successor to the Mighty Wild M400 system. There was a similar system from Olympus but last time I looked I could not find it on their web pages.

The only way to answer your question will be to try it unless you can prevail on someone in the Nikon design bureau or possibly service department to give you some assistance. You will have to simulate the combination of the Zoom optics which are usually keplerian telescopes and the tube lens.

Sometimes they sell parts of things that are systems, separately for custom orders and if this is available for that purpose they may assist you in making it work.

I will send this thread to a list member who works for Nikon. He can probably run down the data needed or just tell you whether it will work or not.

Ichthyophthirius
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Post by Ichthyophthirius »

Hi,

Thank you! Any further information or practical experience would be welcome.

rjlittlefield
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Re: How to find a tube lens for Nikon AZ Plan 5x/0.5 objecti

Post by rjlittlefield »

Ichthyophthirius wrote:Maybe a Raynox DCR-150 (f=125mm) or a 135mm telephoto lens?
I think you mean the DCR-250 (8 diopter). The DCR-150 would be f=208 mm (4.8 diopter).

I've just now tested the DCR-250, and I don't think it will work for your application.

Assuming you're right about the f=100mm tube lens, then the objective must be focal length 20 mm, which at NA 0.5 would also mean 20 mm pupil diameter.

When I test the DCR-250 with a 20 mm aperture, it has a lot of aberration in the corners of APS-C no matter how I orient the lens or where I place the aperture. It's OK even into the corners with an aperture of 11 mm (front-forward, 40 mm separation from lens to aperture), but at 20 mm the spherical aberration gets pretty bad.

Using a 135 mm telephoto would be a better bet, but it will have to be a fast lens in order to tolerate the objective's large aperture without vignetting.

--Rik

Ichthyophthirius
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Post by Ichthyophthirius »

Hi Rik,

Thank you for your suggestions. Yes, I was thinking of the DCR-250. I'm wondering where I could read up on this to get an idea what I'm doing. Is this a similar situation, optically, to mounting a reversed lens in front of another objective? I've never done this before.

I have the very common Prakticar 2.8/135 teleobjective that I will use for a test. Physically, the open aperture of this objective has a diameter of 21 mm http://www.praktica-collector.de/Pentac ... .8_135.htm

Can you suggest anything a priori about the distance needed between the Nikon objective and the camera objective?

Regards, Ichty

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Post by rjlittlefield »

Ichthyophthirius wrote:Is this a similar situation, optically, to mounting a reversed lens in front of another objective?
Optically, it's identical. The only difference is that the microscope objective is already mounted as what would be "in reverse" for a landscape lens, with the finite conjugate facing the subject and the infinite conjugate facing the camera.
I have the very common Prakticar 2.8/135 teleobjective that I will use for a test. Physically, the open aperture of this objective has a diameter of 21 mm http://www.praktica-collector.de/Pentac ... .8_135.htm
Do you mean that the aperture of the Prakticar is 21 mm? If so, that must be a physical dimension inside the lens. The bundle of rays that the lens accepts must be diameter 135/2.8, about 48 mm. This is on-axis; the off-axis bundles may be smaller, which is a common cause of corner darkening even when the telephoto is used by itself.
Can you suggest anything a priori about the distance needed between the Nikon objective and the camera objective?
As close as possible is usually best. When two lenses are combined like this, it is very common for off-axis rays to get blocked by the aperture of the rear lens. This produces vignetting. How bad the effect is, depends on details of the lens design, in particular how far back the entrance pupil of the rear lens is placed. This can be anywhere from almost the front of the lens, to almost back at the camera. You can get a good idea by just stopping down the Prakticar and looking into the front of the lens to see where the aperture appears to be. The farther back it is, the more likely that you'll have trouble with vignetting. See http://www.photomacrography.net/forum/v ... 667#131667 for more discussion.

If the telephoto does not work with the AZ Plan Fluor objective, then another good bet would be an enlarging lens or view camera lens with similar focal length. Usually these lenses use a shorter design that puts the entrance pupil closer to the front.

--Rik

JohnyM
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Post by JohnyM »

Sorry for digging up this topic, but im interested in those objectives. Does anyone have any experience with those?
5x/0,5 should be very nice even with longer tube lenses.

Hokan
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Nikon AZ objective adapters

Post by Hokan »

Hi Ichthyophthirius,
I have the Nikon AZ Apo 4x, NA 0.4, WD 20mm, and the Nikon AZ Apo 1x, NA 0.1, WD 35mm. Awhile back www.Rafcamer.com made some tube lens adapters for me. The AZ100 objectives/lenses have a male thread of M38x1.25. The adapters Rafcamera made for my Nikon AZ100 objectives screw on with no problems. Rafcamera adapters are M38x1.25 female thread to M42x11 male thread. SKU 0711332402096, I believe. Cost $24.95 each.

regards,
Hokan
SOM, (Son Of Multiphot), a DIY macro/micro rig.w/120, 65, 35, 19mm Macro-Nikkors, Nikon AZ100 1X and 4X objectives. Nikon Plan Fluor W objectives, 10X, 20X, 40X.
Zeiss Axiomat, incident BF, DF, DIC, Pol, Phase. With Zeiss infinity objectives, LD, Epi, APO, Plan types.

Pau
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Post by Pau »

I have the same 4/0.40 and 1/0.1 AZ Pan Apos. I've most tested the 4X both with the Canon 70-200 f4 L IS and with the Sigma LSA as tube lenses
It provides a Field with of almost 3mm with APSC, about 10X with a 200mm TL
I bought them with high hopes but I'm not very happy with them: The center of the image is brilliant but the periphery degrades a lot even at 200mm with APSC.
My best results are with the Canon but the corners are not good. Maybe with a 300mm tube lens it would be more useable.

Later I bought the Zoom intermediate piece of the AZ100, I have it custom mounted with the LSA. Now I'm in the point of testing it.
It provides a zoom linked aperture diaphragm that stops down the lens at magnification settings from 1X to 6X (plus another manual driven diaphragm) With the zoom body the field is highly reduced, the vignette only disappears at 3X setting. The IQ is not better, maybe worse, than with the tube lens alone, there are visible chromatic aberrations. This provides around 2.5mm field with APSC and LSA, about 11X

Another not so desirable feature is the working distance, about 20mm with the 4X but not very convenient because of the wider diameter of the lens.

Be aware that it needs to work with a 1/4 plate or equivalent optical window, without it it suffers fro spherical aberration degrading the image.

The official magnification is computed for a FN of 22 mm eyepieces (FN 11mm at the original camera port)
Pau

JohnyM
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Post by JohnyM »

This is all very interesting Pau, thank you.

Im thinking, what might be a better approach. AZ 4x/0.4 pushed up to 12x with 300mm tube lens or 20x/0.4 pulled down to ~12x.
Since i want to use full frame camera my FOV with 300mm should be roughly similar to 200mm on aps-c. So as far as i understand, this wouldnt work very well. Could you provide a picture of some flat test subject with your setup?

Disregarding of IQ, when does it start to vignette on 70-200?

Later I bought the Zoom intermediate piece of the AZ100, I have it custom mounted with the LSA.
Do you know where tube lens is located in AZ100? Isin't it part of the zoom piece?

Pau
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Post by Pau »

Hi Johny,
- Vignette appears at about 140mm with the Canon, but 200mm is much more convenient because the limited high quality image circle
- I can't say for sure, I think that the original tube lens might be placed at the base of the head like in the classic microscope configuration. I put the LSA just over it (its diameter doesn't allow for fitting it inside the dovetail)
- I'll post few sample images or links latter, right now I'm processing a stack.

I plan to make a post about this equipment but I'm slow...this info is an advance.
Pau

ChrisR
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Post by ChrisR »

Yep, sharp in the middle but not a big enough image circle to be very useful on FF.
Not sure it matters, but the objective rear focal plane of these is outside of the objective. It means you can add a phase ring there, but you might not want a lens that close.
Chris R

JohnyM
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Post by JohnyM »

@Pau Thanks for additional info. Cant wait for your results!
@ChrisR I suspected that image circle might be very small, but the way i think about it is 12x/0.4 (300mm tube) which is quite impressive on paper.
Also longer tube gives much more infinity space when compared to short one
and it's 300mm for AZ vs ~120mm for 20x objective.

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Post by rjlittlefield »

JohnyM wrote:it's 300mm for AZ vs ~120mm for 20x objective.
Is the 120 mm a problem? My Mitty 20X NA 0.42 works great on Canon 100 mm f/2.8 US ISM macro, giving 10X NA 0.42, and sharp all across APS-C.

--Rik

JohnyM
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Post by JohnyM »

20x lens i've tested, covers FF sensor on 135mm tube, but with ~1,5mm infinity space.

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