10 JML 21mm f/3.5 lenses here

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johan
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Post by johan »

Here you go, this is the spec sheet she sent me. She did mention they'd done several 21mm f/3.5 lenses in the past so I'm not sure this is the same one? Looks to me like the writing is in a different place and the dimensions on the one we use and like are longer?

Image
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johan
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Post by johan »

Fyi, I showed the lady from JML this thread and she was tickled pink. She is in fact a photography enthusiast herself, she may register here and if so you'll have a JML rep here that might be able to answer questions like yours Canonian.
My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.

Pau
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Post by Pau »

Johan, thanks for your response and for posting the image.
I hope she may told us the original purpose of the lens.
Pau

canonian
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Post by canonian »

:) Ah, the true spirit of the community is back : helping each other out.
Valueble info, thank you so much for doing this , Johan.

conkar
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Post by conkar »

canonian wrote:
Acon wrote:But I don't know how long should the bellow to be.
Does anyone know the optimum tubelength?
I have seen some wonderful pictures, using 50-60mm distance. Not a standard tubelength.
Magnification varies between 3x - 7X, fitting nicely in the range of objects already aquired and their usable magnification.
I think the title in this topic/thread is wrong, the JML 21 3.5 is not a finite microscope objective.

It's a 21mm lens with an aperture of F.3.5, a piece of glass that needs extension to get some magnification.

A very simple calculation would be:

Magnification=extension/focal lenght.

So with 50mm extension and the distance to the sensor (canon 44mm) the magnification might look like this : 94/21=4,48X

Compare the use and glass with Macro Nikkor 19mm F2.8, Zuiko Auto-Macro 20mm F2.0 and the lens you come closest to the Canon FD Macrophoto 20mm F3.5.

Regards,
Conny

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Post by rjlittlefield »

johan wrote:Here you go, this is the spec sheet she sent me. She did mention they'd done several 21mm f/3.5 lenses in the past so I'm not sure this is the same one? Looks to me like the writing is in a different place and the dimensions on the one we use and like are longer?
The writing is definitely in a different place than shown, but all the dimensions that I've checked match to within measurement error.

Those dimensions include overall length of the housing (28.9 vs 28.87 nominal), approximate insets of front and rear lens surfaces, and optical parameters: magnification of 1/0.083 (vs 0.0827 nominal) and a working distance of 13.2 mm (vs 13.414 nominal) when focused on 252.4 mm of extension from sensor to the ringed end of the housing.

I notice that under these conditions, the lens is specified as having an angle of view of about 44 degrees. That's a very wide field compared to a microscope objective, consistent with the corner-to-corner sharpness that that we're accustomed to seeing with our lenses.

--Rik

johan
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Post by johan »

Excellent. What a fabulous lens this looks to be! So the good news is for everyone else reading is that if anyone else also wants one they do have a few available at 300US. The sales contact is kathleens at jmloptical dot com. Unfortunately I'm not able to stretch to that. I hope you all enjoy.
My extreme-macro.co.uk site, a learning site. Your comments and input there would be gratefully appreciated.

DaveinMpls
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Lens in stock at JML Optical

Post by DaveinMpls »

I just spoke with Kathleen Schwartz at JML Optical Industries about the JML 21mm f3.5 lenses she has in stock. She used to work in Quality Control and personally examined their stock. She now has 8 lenses which meet her very high standards of quality optically. Others in stock may be as good but have not yet been inspected. The price is indeed $300 plus shipping for what appears to be a unique lens. She couldn’t believe that the old stock 21mm lenses had sold for as little as $10 per lens several years ago.

Pau
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Post by Pau »

DaveinMpls, could you ask her what is the original application of the lens?
Pau

DaveinMpls
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Post by DaveinMpls »

[quote="Pau"]DaveinMpls, could you ask her what is the original application of the lens?[/quote]

Hi Pau,
When I spoke with Kathleen earlier today she said, “This is not an objective, it is a wide-field, high-resolution optic.” I did not ask specifically what application it was designed for. She was VERY happy with the quality of the 8 lenses she had personally selected from their existing inventory. She said that not every lens meets their design specifications.

I told her that if JML makes any other high resolution lenses of similar quality, that members of our forum would like to hear about them, especially if they cover other magnification ranges. Apparently she is very busy just now, so I don't know if she will be able to help us with that. But she is a really a genuinely helpful person. She can be reached at the e-mail address listed above.

DaveinMpls

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Post by rjlittlefield »

conkar wrote:I think the title in this topic/thread is wrong, the JML 21 3.5 is not a finite microscope objective.
Yes, the term "finite objectives" is misleading here. I've edited the title of the thread to say just "lenses".

--Rik

Acon
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Post by Acon »

rjlittlefield wrote:
conkar wrote:I think the title in this topic/thread is wrong, the JML 21 3.5 is not a finite microscope objective.
Yes, the term "finite objectives" is misleading here. I've edited the title of the thread to say just "lenses".

--Rik
So, what if I attach JML 21mm to any tube lens or regular telephoto like Nikon 200mm f/4 or 70-200mm f/2.8? What would happen? :D

I don't have the adapter of JML 21mm yet so I can't test it, just curious.

rjlittlefield
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Post by rjlittlefield »

So, what if I attach JML 21mm to any tube lens or regular telephoto like Nikon 200mm f/4 or 70-200mm f/2.8? What would happen?
It probably works fine, albeit with a bit of spherical aberration from being used farther away from its design point.

From my standpoint, and I think from Conny's, the issue is that the JML 21 doesn't act like any microscope objective.

Based on the spec sheet from JML, we now see that the lens is designed for use as what we would consider reversed, at 12X (1/0.0827), over a field whose diameter is 17.86 mm, with a numerical aperture about 0.13.

In contrast, a typical 10X microscope objective would have an NA of 0.25 but a field diameter of only 3 mm. Even the Nikon CFI60 10X NA 0.25 (20 mm FL) only goes to around 5 mm field diameter.

So in the JML we're looking at a lens that has an odd mount and is designed to cover a much wider field at roughly half the resolution of a microscope objective that has similar focal length.

Based on the spec, it would make a great lens to stick on a medium-format camera. I'm having visions of stacking at 10X on a Hasselblad H4D-200MS camera, covering an area that's only 3.7x4.9 mm with 200 megapixels. OK, that might be going a bit far, but even the 50 megapixel version would still be pretty cool! I'm especially amused by the concept of sticking a $22K camera behind a $25 lens, even behind a $300 lens, and very reasonably expecting the lens to hold up to the experience.

--Rik

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Post by ChrisR »

It would lend itself to "tilting and shifting", but I don't think I have a problem with converging verticals at 5:1 .

On the other hand there are a few ways to move the sensor about, while holding subject and lens still, to build a pano within the coverage of the lens. None of them very cheap or easy though.
I'm wondering about reversing a Nikon PB-4 bellows and using its "shift" of about 20mm.
On a Nikon D800 that would yield eg (a 36 x 44mm image) , 66MPx, in two exposures

Craig Gerard
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Post by Craig Gerard »

I'm wondering about reversing a Nikon PB-4 bellows and using its "shift" of about 20mm.
Chris,

I tried this recently. You'll need to add additional extension tubes for the camera to clear the 'swing' and 'shift' levers, otherwise, it is diffcult to properly orientate and secure the camera. The additional extension defeats, to some extent, the purpose of the exercise .ie. swing/shift the camera standard rather than the lens :(


Craig
To use a classic quote from 'Antz' - "I almost know exactly what I'm doing!"

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