ZEISS photo eyepiece Projektiv

75RR · Post by **75RR** » Tue Jan 26, 2016 3:26 pm

Am using a Zeiss 12.5x KPL eyepiece (which I elevate 15mm which gives 1.8x if my calculations are correct) as a projector lens at the moment.
It works quite well I think.
Saw this today and it got me wondering if it might be better.
I don't understand the f = 125 designation, was expecting something like 1.6x or 2x.
Does any one know if it will be an improvement?

http://www.ebay.com/itm/221982311034?ru ... 26_rdc%3D1

Pau · Post by **Pau** » Tue Jan 26, 2016 3:36 pm

There are lots of models of Zeiss Jena projective photoeyepieces, some of them marked with magnification, others with what seems the focal lenght like the one linked.

I don't know if their compensation is the same than Zeiss West, an info I would like to know.

75RR · Post by **75RR** » Tue Jan 26, 2016 3:48 pm

The projective photo-eyepiece says Made in West Germany so probably ok on compensation, the length worries me a bit, seems excessive, + not sure of the magnification.

Pau · Post by **Pau** » Tue Jan 26, 2016 4:16 pm

Yes, I didn't read the engravings!

It may be for projection on opal glass or even for wall projection, just a guess.

75RR · Post by **75RR** » Wed Jan 27, 2016 2:09 am

Found some additional info by Enrico Savazzi who tried out the Carl Zeiss (West) Projektiv f=125mm on a m4/3 camera and was not convinced.
He says it produces "poor image quality on most of the image circle."

http://www.savazzi.net/photography/zeissadapter.html

This is the page on Microprojection eyepieces in the Zeiss Optical Systems brochure.
What I took to be excessive length would seem "normal".
Still need someone to clarify things a bit. I have a micro 4/3 camera.

Ichthyophthirius · Post by **Ichthyophthirius** » Wed Jan 27, 2016 6:18 am

Hi,

I think Enrico tested the Projektiv without a relay optic, just by direct projection. http://www.photomacrography.net/forum/v ... 214#152214 However, the Mipro Kpl (older) and Projektiv (did later replace the Mipros) project at infinity. You have to use a relay optic to get an image with a shorter camera length (camera objective focussed to infinity).

For m4/3, you need an overall relay factor of 1.1x to 1.2x to capture a large field. Eyepiece magnification of the Projektiv f=125 is 2x

1.2 = 2 * 0.6
0.6 * 250 mm = 150 mm (Please correct me if the calculation is wrong; seems to be the range as in the Zeiss table above: 1x: 125 mm; 1.25x: 160 mm)

You'll need a camera lens around 150 mm, maybe a darkroom lens. Also, the entrance pupil of the relay optic must be situated 1-2 cm above the eyepoint (30 mm), so the distance between Projektiv and the relay optic can be several cm, just vary it until you find the ideal spacing.

The other Mipros, 63 mm and 80 mm, are outstanding photo eyepieces for APS-C when used with a suitable relay optic. I've never seen a test of the 125 mm.

Regards,

Ichty

g4lab · Post by **g4lab** » Wed Jan 27, 2016 10:02 am

I currently have an Olympus FK 125 3.3x photo ocular on ebay. If anyone here can use it I will cancel the auction and sell it directly.

Olympus ocassionally copied or quoted Zeiss on things and a few are interchangeable. I don't know the age of this optic nor how much compensation it has. It is clean.

Alan Wood · Post by **Alan Wood** » Wed Jan 27, 2016 10:56 am

The Olympus FK photo eyepieces are compensating and were intended for use with the short-barrel objectives used on the BH and CH microscopes.

http://www.alanwood.net/photography/oly ... es.html#fk

They project an image onto the film in a camera, not across a room onto a screen.

Alan Wood

75RR · Post by **75RR** » Wed Jan 27, 2016 11:21 am

You have to use a relay optic to get an image with a shorter camera length (camera objective focussed to infinity).

Was hoping I could use it directly as a projector lens. Pity
Thanks all

Just realized that the text says the same thing. (Have highlighted the relevant part)

g4lab · Post by **g4lab** » Wed Jan 27, 2016 5:51 pm

They project an image onto the film in a camera, not across a room onto a screen.

There isn't much difference between the two functions. Both are flat field just different distances and ultimate magnification.

Zeiss and Leitz (And Bausch who also used Zeiss as a design bureau) used the same projectives for both purposes.

enricosavazzi · Post by **enricosavazzi** » Thu Jan 28, 2016 5:26 am

Ichthyophthirius wrote:I think Enrico tested the Projektiv without a relay optic, just by direct projection. http://www.photomacrography.net/forum/v ... 214#152214 However, the Mipro Kpl (older) and Projektiv (did later replace the Mipros) project at infinity. You have to use a relay optic to get an image with a shorter camera length (camera objective focussed to infinity).

That is correct, I tested without relay optics and without having any information on this eyepiece.

My solution to the problem was using an ordinary high-eye-relief 10x objective and a 30 mm camera lens on Micro 4/3. This worked well, and I never revisited the other eyepieces.

harisA · Post by **harisA** » Thu Jan 28, 2016 8:17 am

I have personally used a S-KPL eyepiece which are superior to kpl but very expensive and hard to find.These are not optimised for direct projection but instead requiring a lens of about 35mm focal distance to cover m43.A 65mm is adequate for FF.

Ichthyophthirius · Post by **Ichthyophthirius** » Thu Jan 28, 2016 9:18 am

g4lab wrote:
They project an image onto the film in a camera, not across a room onto a screen.
There isn't much difference between the two functions. Both are flat field just different distances and ultimate magnification.

There must be subtile differences; the two functions can't really be achieved with the same optic to the highest standard.

For example, Olympus NFK projectives are designed for short distance projection (125/150 mm). Lots of people would like to have the NFK 1.67x for use with an APS-C sensor and it's expensive (> $400).

It would be easy to use a cheap NFK 2.5x (< $100) with a matching camera lens (as you would with a Zeiss Mipro), but it doesn't work well, you can't even get it parfocal. Otherwise everyone would do it.

Regards,

Ichty

Ichthyophthirius · Post by **Ichthyophthirius** » Thu Jan 28, 2016 9:28 am

enricosavazzi wrote:This worked well, and I never revisited the other eyepieces.

Hi Enrico,

Maybe you should have another look. The performance, at least of the smaller Mipro 63 and 80 together with a relay optic, is outstanding: http://www.mikroskopie-ph.de/Vergleich-MC63-Elmar.jpg

rjlittlefield · Post by **rjlittlefield** » Thu Jan 28, 2016 12:18 pm

Ichthyophthirius wrote:
g4lab wrote:There isn't much difference between the two functions. Both are flat field just different distances and ultimate magnification.
There must be subtile differences; the two functions can't really be achieved with the same optic to the highest standard.

I see two differences, which can be subtle or not depending on exactly how you use the eyepieces.

One difference is that the eyepieces themselves are optimized for different focus conjugates. As with all lenses, when you drag them away from their design point, they will pick up some aberrations and curvature of field. This will be evident when pulling the screen projection eyepiece farther out of the tube in order to make it project onto a nearby camera sensor. Charles Krebs has a nice page illustrating this effect even with much smaller changes: http://www.krebsmicro.com/NFK_lowermag/index.html .

The other difference is closely related, but really applies more to the objective than to the eyepiece. If somebody new to the field tried to use the screen projection eyepiece with a camera but not pulling it out of the tube to make the focus correction, then they would be forced to refocus using the knobs on the microscope. Doing it that way also drags the objective away from its design point, which with a large NA objective can be catastrophic.

--Rik