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PostPosted: Tue Feb 12, 2019 2:20 am 
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hi
i want to know,why this lens named 0.32x, not 3.2x,not 0.6x,or any number else ?
can it be used as 3.2x or 0.6x by adjust work length and focal length ?
how can i know (or calculate)its focal length,


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PostPosted: Tue Feb 12, 2019 11:26 am 
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92111 wrote:
hi
i want to know,why this lens named 0.32x, not 3.2x,not 0.6x,or any number else ?
can it be used as 3.2x or 0.6x by adjust work length and focal length ?
how can i know (or calculate)its focal length,

https://www.physicsclassroom.com/class/ ... -of-Lenses
It is very easy to know the focal length approximately: open the window and let direct sun light come inside. Hold the lens perpendicular to the sun rays. Place a flat piece of bright colored ceramic tile or a very flat stone or a flat piece of bright-colored metal sheet (not paper! not cardboard!) parallel to and behind the lens. Move the lens until the smallest possible spot of light (namely: the Sun's image) appears on the plate. Measure the distance between the lens and the plate (be careful not to place your fingers in the light path, to avoid burns). That distance is the focal length, because the sun rays arrive from infinity (150 million km away). For very accurate determination of the focal length you need an optical bench and other gadgets.
You cannot adjust the focal length, it is a fixed property of the lens geometry.
The magnification 0.32X is achieved within the mode of use, in this case, for microscopy, between the eyepiece and camera.

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PostPosted: Tue Feb 12, 2019 12:36 pm 
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Hobbyst46 wrote:
92111 wrote:
hi
i want to know,why this lens named 0.32x, not 3.2x,not 0.6x,or any number else ?
can it be used as 3.2x or 0.6x by adjust work length and focal length ?
how can i know (or calculate)its focal length,

https://www.physicsclassroom.com/class/ ... -of-Lenses
It is very easy to know the focal length approximately: ...

Very true for a positive lens; but it seems likely that this one is negative.
... fortunately, these are also covered in your helpful link.

MichaelG.

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PostPosted: Tue Feb 12, 2019 1:22 pm 
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MichaelG. wrote:
Hobbyst46 wrote:
92111 wrote:
hi
i want to know,why this lens named 0.32x, not 3.2x,not 0.6x,or any number else ?
can it be used as 3.2x or 0.6x by adjust work length and focal length ?
how can i know (or calculate)its focal length,

https://www.physicsclassroom.com/class/ ... -of-Lenses
It is very easy to know the focal length approximately: ...

Very true for a positive lens; but it seems likely that this one is negative.
... fortunately, these are also covered in your helpful link.

MichaelG.
Here, at the bottom of the linked page, is a trick to utilize the same rays from the same Sun to find the focal point of a concave lens.
http://www.cbakken.net/obookshelf/ccfocal.html

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Zeiss Standard GFL+Canon EOS-M10, Olympus VMZ stereo


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PostPosted: Tue Feb 12, 2019 7:16 pm 
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Joined: Tue Jun 14, 2016 11:01 pm
Posts: 132
Location: Surrey, UK
I have one of those, after your recent post, c/o John Mr Sonchus.
Yes it's a negative lens, a bit like a teleconverter.


Does anyone know if it would have "compensation" built in to correct for chromatic aberration in the Leitz objective?


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PostPosted: Tue Feb 12, 2019 9:21 pm 
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Location: Cumbria, UK
Hi, yes my Leitz phototube assembly has this reduction lens incorporated.
It reduces I believe the final image, after it's been corrected ALA Periplan (to match the objectives) eyepiece, projection preferably. That said I doubt very much that this lens has correction, meaning presumably that it's also suitable for use as the final pre-camera-sensor reduction lens for other systems, assuming that the image going into it is fully corrected.

A handy lens that is worth holding on to....

John B.

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PostPosted: Wed Feb 13, 2019 8:11 am 
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Joined: Thu Dec 15, 2016 6:32 am
Posts: 34
I'm no expert in Leitz material, but this 0.32x adapter should come after the Periplan ocular right?

The ocular will project the primary image to infinity, so there is a need for a converging lens to focus the image on the film. (It should be a positive lens.)
Going through some Leitz material, this lens when matched with a Periplan 10x would fill 24x36mm film format.

The 10x indicates f=25mm for the ocular, the final magnification would be 0.32x10=3.2 and using the equation f(converging lens)/25=3.2 the focal length of the reducing lens will be 80mm.

Hope this helps.

Cheers,
John


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PostPosted: Wed Feb 13, 2019 9:17 am 
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Location: Surrey, UK
So, raising and lowering it would alter the size of the image.

It's designed for 24x36mm.

Edit this bit's all wrong, I thought it was a negative lens - may as well delete it...
[
]

Somewhere I have an adjustable Panagor zoom macro teleconverter which moves a negative lens element inside it when you turn the barrel. It has no floating elements, they move as a block.
Hmmm, I wonder if Leitz do it better than Panagor :?

I'm not sure if there is anything clever about the Panagor which enables it to hold the distance-to-sensor constant.
I think I need to do some maths to work out what a "thin" negative lens would do!! WHere does the image focus, as you move the negative element up and down?

There are some on ebay now: eg
https://www.ebay.co.uk/itm/Panagor-Auto ... rk:22:pf:0


Last edited by ChrisR on Wed Feb 13, 2019 11:57 pm, edited 1 time in total.

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PostPosted: Wed Feb 13, 2019 9:24 am 
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Hi Chris,

Well, if the reducing lens is focused to infinity on the camera (think of it as a infinity setup, the ocular as the objective, and the reducer as the tube lens)
raising and lowering would not affect magnification. However, the exit and entrance pupils might have a mismatch which would cause vignetting.

Here's the total setup after some googling.

https://www.mikroskopie-forum.de/index. ... ic=25092.0

Regarding the Panagor macro extender you mentioned, that's one clever thing!
Googled the patents for it.
https://patents.google.com/patent/US403 ... Obreschkow

It's essentially a rear placed teleconverter (which is a negative lens). The magic behind it is, that the lens group is movable.
If the lens group is advanced forward, it will project an image that is closer to the master lens (i.e. larger magnification)


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PostPosted: Wed Feb 13, 2019 10:25 am 
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Joined: Thu Jul 26, 2018 8:45 am
Posts: 151
hi everyone .... i want to know more?
1.what is that lens ????
2.d1=80mm right ??? abednego1995


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PostPosted: Wed Feb 13, 2019 10:50 am 
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abednego1995 wrote:
Regarding the Panagor macro extender you mentioned, that's one clever thing!
Googled the patents for it.
https://patents.google.com/patent/US403 ... Obreschkow

It's essentially a rear placed teleconverter (which is a negative lens). The magic behind it is, that the lens group is movable.
If the lens group is advanced forward, it will project an image that is closer to the master lens (i.e. larger magnification)

Thanks for the patent link.
Frankly though; I'm surprised that Dallmeyer gets no credit.

This fascinating little book describes the origins of the telephoto lens
https://archive.org/details/telephotographye00dallrich/page/n10

MichaelG.

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PostPosted: Wed Feb 13, 2019 11:14 am 
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Thoughts:
The schematics of the optical path as shown above show that the 0,32X lens is a concave, diverging lens.
The explanations in the German forum linked above say that this reducing lens should be used afocally, that is with a lens on the camera. As far as I could read.

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PostPosted: Wed Feb 13, 2019 12:44 pm 
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I don't think we're there yet.
I have the Leitz fitting, which goes with its film camera - no other lens is in there, no "camera lens".

I was wrong, it's a positive lens. It's still in the camera , but I'd say 80-100mm FL.

So it works on a very small angle of light which somes from the Periplan, up through a small hole in the shutter assembly which is a few (4?) inches deep.
As such it's not much direct use to me, I don't really want just the middle of the view.
Maybe it'll make a good short "tube" lens with an infinite objective. The T2 thread makes it easy to try.


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PostPosted: Wed Feb 13, 2019 1:03 pm 
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Here's my adapter, comprising this lens, as fitted to my Orthoplan. It works perfectly and is parfocal with the objectives. The adapter-ring at the top in my case is for my Canon 1200D, but can be for any camera, just requiring the appropriate adapter-ring in it's place....

Image

Image

Image

Image

Image

John B.

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PostPosted: Wed Feb 13, 2019 1:25 pm 
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Posts: 34
>92111

I'm not sure what device the schematic shows, are those components within??
Quote:
i want to know,why this lens named 0.32x, not 3.2x,not 0.6x,or any number else ?
can it be used as 3.2x or 0.6x by adjust work length and focal length ?
how can i know (or calculate)its focal length,


Answering your initial question, you'll have to change the focal length of the lens in order to change the magnification.
Using a zoom-lens might work, but as I wrote before, you have to know where and how large the exit pupil of the ocular is and the same for the reducing lens.
If those don't match you will get vignetting.

>Michael

Yep, they should've mentioned Dallmeyer. But looking at the patent, I doubt they made the optics themselves as they don't claim anything optical.

>Hobbyst46

I also don't read German, but an afocal setup like that in the German forum would result in imaging a different image plane than the primary image plane.
I think the idea behind is optimizing the projected image to an APS-C sensor rather than a full-sized sensor. It'd work for low NAs, but for high NA work it
will effectively change the TL, introducing unwanted aberrations.

Here's a great reference... by Leitz
http://www.science-info.net/docs/leitz/ ... -15-64.pdf

>John

PUURFECT!
Leitz seems so effective clearing the web of old manuals and brochures... I can't find documentation illustrating photographic systems...
That would be the intended setup.


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PostPosted: Wed Feb 13, 2019 11:45 pm 
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Location: Surrey, UK
Good find, JohnAbed.

JohnSonch, how much of the obvective's field are you getting on the sensor?
If this is covering 36mm with an 83.3mm FL, we'd need 83.3/36 x 22.3 for APS, right?
That's 51.6mm.
I can find something close to that...


Meanwhile, I'll try this lens in a regular infinity setup. Some of the Mitutoyos have very wide coverage (7.5x , 20x, 100x I think) which might cover APS giving me 3.12x at NA 0.21 , 8.3x NA 0.42, 42x NA 0.7 . Unspectacular except they have very long working distances too :).


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