CZJ EDF 7x40 Roof Prism Binoculars (1 Viewer)

Post-WWII, the East German company of Carl Zeiss Jena produced two roof prism binoculars for the commercial market, the Notarem 8x32 and 10x40
see posts #62 and #63 at: https://www.birdforum.net/showthread.php?t=385822&page=3

CZJ also produced a different model specifically intended for military use, the EDF 7x40
(as there’s a lot of detailed information available about the EDF, for convenience I’ve listed the main links in the final post)


EDF 7x40
The EDF 7x40 was introduced in 1981. See an image from Frank Weissörtel at: https://www.flickr.com/photos/114212355@N05/48975070751
(the hole in the left prism plate is where the IR detector was, see post #4 below)

It was specifically designed for the army of the then nation of East German: the NFA/ Nationale Volksarmee of the DDR/ Deutsche Demokratische Republik
Köhler indicates that it was the result of 10 years of development, so the initial work would have dated back to the early 1970’s
(and presumedly the civilian models were an offshoot of the programme)

EDF is an abbreviation of Einheitsdoppelfernror which means ‘double telescope unit’ or ‘binocular unit’. It replaced the Porro prism DF 7x40 binocular


Identification, Design Philosophy and Durability
The EDF is immediately recognisable by the placement and asymmetric design of its hinges

As a product of the cold war era, the EDF includes provision for the most pessimistic of uses - remaining serviceable in a battlefield with high levels of background radiation

It is also known for its extreme durability e.g. see the detailed testing requirements described in the Thürnagel and MosMilTec links
This is one instance where a military binocular does differ significantly from its civilian versions

And consistent with it’s most dire usage, all of the rubber armour is user removable and replaceable; see the images from: https://m.blog.naver.com/juniell/220727060712


Optics
The commercial Notarem 8x32 and 10x40 models, seem to have the same optical construction,
with the 10x40 having a longer objective body and larger diameter objective lenses of the same pattern as the 8x32

However, while the Notarems and the EDF share a common origin, they differ in a number of ways. Firstly the EDF is an IF rather than a CF design
And it also has a number of significant optical differences


A) CONSTRUCTION
As can be seen from the images from Marco Gherardi and Holger Merlitz - compared to the Notarem 10x40 - the EDF 7x40:
- appears to have the same Schmidt-Pechan prisms (?), though presumedly in a much more substantial mounting cradle

- has a similar 2 lens/ 2 group tele-objective (though the second lens uses special glass, see below), and

- has a modified eyepiece of 5 lenses, with a markedly different rear lens, and seemingly a different spacing of the lens groups (and again the first lens uses special glass)

While the eyepiece lenses appear to be in 3 groups in a 3/ 1/ 1 pattern, as Holger notes the diagram seems to indicate that there is a minimal air gap between the second and third lenses


B) EYE RELIEF
The eyepiece construction results in 20mm of eye relief, intended to allow use with a gas mask


C) SPECIAL GLASS
In place of the usual flint glass lenses, the EDF uses a special version known as SF3R, with the R indicating radiation resistance
Regular flint glass darkens to black as a result of prolonged radiation exposure. The R version glass minimises the problem, though it does not eliminate all darkening
The glass is used for 2 of the lenses: the second lens of the objective and the first lens of the eyepiece; see Köhler


continued . . .

Optics:

Coatings
A) ANTI-REFLECTIVE
As with many other Eastern Bloc military binoculars, the view has a strong yellow hue intended to increase contrast under low light/ low contrast conditions
Various sources indicate that this is primarily due to the SF3R glass used for 2 of the lenses
However, since a similar hue is found on the simplified commercial production, the coatings may have also been a significant factor

Gherardi provides a photo of glass ‘Neutrafilters’ that were issued with the units to completely remove the yellow hue,
though presumedly with some loss of transmission and hence brightness


B) PHASE COATING?

The introduction of the EDF predates phase coating (it was first used by Zeiss of West Germany in 1988, and then adopted by others)
Consequently, one would expect the EDF to have a slight softening of detail typical to a ‘de-phased’ image
However, as indicted in various reviews, this does not seem to have been significant in practice at the magnification of 7x

And interestingly, a number of sources mention minimising the effect of the lack of phase coating, by intentionally only looking through half of the exit pupils!
e.g. see Hermann’s comments in post #7 at: https://www.birdforum.net/showthread.php?p=2183730#post2183730

- - - -
The EDF does not have dielectric coating on the one non-total internal reflection surface of the prism pair (the coating was only introduced in the late 1990’s)


Optical Performance
A) ORIGINAL CZJ PRODUCTION
Gijs has tested an Aus Jena unit (Aus Jena was a marking used by CZJ on commercial products sold in the West)
See the attached graph from the May 2016 article ‘Test van historische 40-50mm kijkers . . . ’ at https://www.houseofoutdoor.com/verrekijkers/verrekijkers-testen-en-vergelijken/

The unit may have slightly more transmission than it’s military counterpart with the SF3R glass
And considering the intended uses of the military version, the extreme dip below 500nm would seem to be a significant limitation
However, various sources indicate that the EDF’s performance improves in terms of contrast at twilight e.g. see Uwe Petzold comments in the Thürnagel link


B) LATER CIVILIAN PRODUCTION
Later civilian production originally by Docter and now by Noblex, has a much less tinted image, and likely higher transmission
See both the comments of:
- Hermann at post #4 in the above link, and
- Pinac (aka Canip on Bird Forum) regarding both the CZJ and Docter versions at: https://binocular.ch/the-pinac-collection/#collection

n.b. the Docter production did not use phase coating, and there is no indication that it has been added by Noblex


continued . . .

Military Features
The EDF has a number of additions specifically intended for military use

A) RANGFINDING RETICLE (located in the right hand barrel)
The reticle is a planar glass, located at the focal plane between the prisms and the eyepiece (as seen in the eyepiece cross-section)
The same pattern of reticle is either:
- vapour deposited onto the glass surface, or
- etched into the glass
The latter is necessary to enable the illuminator function


B) TRITIUM ILLUMINATOR (for the reticle)
The intensity of the illumination is adjustable by a ‘dimming switch’ on the right prism cover
(in contrast to the EDF, the previous DF 7x40 used an electrically illuminated reticle via an external power source)

Following the 1990 reunification of Germany, the illuminators were removed from service units as they didn’t meet the West German/ reunited Germany environmental protection laws
n.b. The danger from tritium is not from penetrating radiation but principally if it is ingested or inhaled
So for those who may be tempted to open a unit which may still have its tritium, note the cautions in the linked information!


C) IR DETECTOR (located in the in the left hand barrel)
At the time, many night vision viewers still used active technology i.e. they only worked in conjunction with infrared illumination
To use the detector it had to be rotated into the field of view, see the details as to it’s activation and deactivation from Uwe Petzold in Thürnagel


Dating by Alphabetic Prefix
Military production commenced in 1981. An alphabetic prefix to the serial number identifies the year of production: A through K, for 1981 to 1990
(the letter J is only used in German with foreign language words // EDIT: this is not why the letter was not used, see Arthur's likely explanation in post #8 below)


EDF Versions
While collectors will be primarily interested in the military versions, those seeking a binocular to use will probably be more interested in the civilian production
- especially the more recent units with more neutral coatings, and most probably higher and more even transmission


A) MILITARY PRODUCTION - East Germany (1981 to 1990)
There were 2 versions:
i) with the tritium illuminated reticle (NVA designation: ‘010400’), and

ii) with the non-illuminated reticle (NVA designation ‘010500’; or ‘7x40 oB’, where ‘oB’ means ohne Beleuchtung i.e. ‘without illumination’)
n.b. This could be upgraded to version i) with the inclusion of the tritium unit and replacement of the reticle


B) COMMERCIAL PRODUCTION
Commercial versions lack obvious military features such as: the radiation resistant glass; the reticle; the tritium illuminator and; the IR detector

i) Carl Zeiss Jena
- 7x40 B/GA (1981 to 1990)
These have a strong yellow hue similar to the military production


ii) Docter-Optic (1991 to 2016)
- 7x40 B/GA
- 10x42 B

The first 7x40’s seem to have used left over CZJ parts including lenses, and so have a strong hue. Later production has a much more neutral image
This model was optionally available with a reticle


The 10x40 variation presumedly uses the CF 10x40 commercial model’s optics in the IF 7x40 housing
(Docter produced both the 8x32 and 10x40 commercial versions that originated with CZJ, see posts #62 and #63 at: https://www.birdforum.net/showthread.php?t=385822&page=3 )


iii) Noblex (2017 on)
- 7x40 B/GA
- 10x42 B
These follow on from the purchase of Docter-Optic


continued . . .

Primary Sources

Marco Ghirardi has posted extensive information, including cross-section images on the Binomania forum. See 3 pages starting at: https://binocoli.forumfree.it/?t=69743740

Guido Thürnagel has posted information that can be retrieved using Wayback at: https://web.archive.org/web/20121004182730/http://home.arcor.de/thuernagel/edf.htm ,
https://web.archive.org/web/20021226050247/http://home.arcor.de/thuernagel/dferfahrungen.htm , and
https://web.archive.org/web/20020813194328/http://home.arcor.de/thuernagel/radio.htm
The last addresses in detail the nature of the tritium illumination, and the danger of attempting to remove the tritium source

Albrecht Köhler has posted information that can also be retrieved using Wayback at: http://web.archive.org/web/20181221043422/http://www.akoehler.de/
(click on ‘EDF 7x40’ in the left hand column)

Holger Merlitz has included various detail at pages 8 and 9 of the first edition of his book on binoculars, see the first link from MosMilTec below

Piergiovanni Salimbeni tested the Docter 7x40 B/GA at: https://www.binomania.it/binocoli/docterBGA/docterBGA7x40.php


n.b. All of the above are either in Italian or German. However, Google Translate produces useable results
And thanks to jring for the Wayback addresses at: https://www.birdforum.net/showthread.php?t=375249


The company MosMilTec has additional information:
- user manuals either in English or German at: http://www.eyry.eu/miltec/index.php?option=com_weblinks&view=category&id=11&Itemid=190&lang=en, and
- information from the document ‘A 050/1/501 Einheitsdoppelfernrohr 7x40 reconditioning’ regarding various stress tests, at: http://www.eyry.eu/miltec/index.php?option=com_content&view=article&id=17&Itemid=184&lang=en

And Holger has also provided comparative reviews of two different military units, at: http://www.holgermerlitz.de/edf7x40.html, and http://www.holgermerlitz.de/ior7x40.html


John

John (post #1 to #5)
Many thanks for this wealth of information; great research, excellent presentation! Very useful!!!
Canip

Great work John, thanks.

Lee

John A Roberts said:

Dating by Alphabetic Prefix
Military production commenced in 1981. An alphabetic prefix to the serial number identifies the year of production: A through K, for 1981 to 1990
(the letter J is only used in German with foreign language words)

. .

Click to expand...

Ja?

In the American military, "J" is not used when there is an alphabetical series to avoid confusion with "i" and "j." In handwriting the two could easily be confused. I suspect that the DDR military did the same.


Happy bird watching,
Arthur Pinewood

Thanks for this great collection of info on the EDF. I have one "Einheits-Doppelfernrohr 7x40" (Standard Binocular 7x40) myself, East German military heritage but serviced since then. It's a piece of cold war history: A binocular optimized for nuclear war. Remaining operational -and tested to do so- after receiving ten lethal radiation doses for the guy who was supposed to look through from his ABC-suit. Standard issue for officers back then.

The binocular, while having a yellow tint, is sharp, nice and high quality all around. Especially under bad lighting conditions. While some old hands still say it's Porro-predecessor DF was better optically, Zeiss Jena's civil flagship product back then. The EDF's robustness is unheard of.

BTW: The grey lanyard is made of "Dederon" synthetics. The vocal "DDR" (east Germany) used as a branding name for some of their home grown nylon versions. I see it as a piece of history.

Another amazing article! Thank you John.

New 7x40 EDF Review by Holger Merlitz

Holger has recently posted an additional comparison. This time of:
• a 1987 military Carl Zeiss Jena 7x40 EDF - with the original strongly yellow image, and

• a current civilian Noblex 7x40 B/GA - with a brighter and near neutral image (see the attached photograph)


The Noblex lacks the obvious military features of the reticle and the tritium illuminator, along with the radiation resistant glass
And as it also has significantly improved coatings, it has an overall improved optical performance
However, the performance suffers slightly from the lack of a light shield that was present on the original EDF


The comparison takes the usual form of Holger’s structured reviews, and can be found at: http://www.holgermerlitz.de/old_vs_new/edf_noblex.html
And as usual it's an interesting an informative read


John

Awesome, John! Incredible information put together.

Many Thanks!

PHA

It's surprising how much the top one in that picture still has a yellow colour cast.

Hi Mark,

As I noted in post #3, the original CZJ production from 1981 to 1990, had neither phase coating nor dielectric coating on the Schmidt-Pechan prisms

Phase coating of the two roofed surfaces was first introduced on binoculars in 1988
It addressed the slight softening (de-phasing) of the image as the light column was split and then recombined as it was reflected from the two roof surfaces

Dielectric coating of the one non-Total Internal Reflection surface, was first introduced on binoculars in the late 1990’s
Prior to it’s introduction usually either silver of aluminium was used. Both are deficient in the blue portion of the spectrum, which results in a slightly yellow reflection

- - - -

We know that phase coating has not been used on either the later Docter or the the current Noblex production
And the slightly yellow Noblex image - while employing more modern anti-reflective coatings on the lenses -
may be consistent with the continuing use of either silver or aluminium on the non-TIR prism surface

In this regard, while both the Noblex website and catalogue comment on the lens coatings, there is no mention of prism coatings
The 31 page/ 6.3 MB catalogue can be found at: https://noblex-germany.com/index.php/en/service/downloads


John

John (post #11),
Thank you for posting the link (I had not visited Holger‘s great website for a while and had missed that review).
:t:
Canip

Aus Jena Review

There is a recent thread on Cloudy Nights that contains additional information and images by Carlos/ Coracoli78
at: https://www.cloudynights.com/topic/713108-carl-zeiss-jena-7x40-bga-a-personal-review/#entry10283751

It includes Carlos’ observations about the optical performance of the commercial version produced by CZJ
- the Aus Jena marked model which was made from 1981 to 1990



John

Thank you John for taking the time to put this wealth of information together. I have the Docter 7X40, a nice tough glass. I have the original EDF 7X40 somewhere. I really love the view of the 7X40 DF, the predecessor with the wide FOV.

Andy W.

Transmission Comparison of Commercial Production: Aus Jena vs Docter

Gijs’ recent publication 'Investigation of Historical 7x42 Binoculars’ compares the above,
see at :https://www.houseofoutdoor.com/verrekijkers/verrekijkers-testen-en-vergelijken/

While the earlier Aus Jena has a slightly higher peak transmission, the Docter’s overall transmission is far more even,
and notably better towards both ends of the transmission range

In looking at the graph, it should be kept in mind that production of:
• the Aus Jena spanned 1981 to 1990, and
• the Docter from 1991 to 2016
So how typical either unit is of their respective production is unknown

With transmission between 60 and 74%, the Docter unit is lacking when compared to what would be expected
of even modestly priced current commercial production


John

John (post # 18),

thank you for this.

As a side note, I recently compared the color bias of the CZJ versus the two versions of the Docter I have, see attached.
Unfortunately, I don't know the production dates of the Docters.
"Docter One" has serial no Q 0900003, "Docter Two" has Q 0900048.

The differences are quite visible, even between the two Docter binos.

Pinac

Hello,
I had one, the 1987 bought online in 2015 (rubber armoring looks like it is not second hand but fifth-hand).
I bought it from curiosity to spend some time with it and later sold it.
Yellow cast was quite strong, but except this optical performance was quite good for 250 euro.

I believe statement about big exit pupil and small eye pupil in daylight,
may result in good sharpness even without phase coating.

Color cast through contemporary smartphone in attached pictures (one global view, one centerfield cut from original 1MB+ photo)