Carl Zeiss Jena 7×40 B/GA



Objective diameter:  40 mm
Magnification:  7 x
Exit pupil: 5.71 mm
IPD: 56  –  78 mm
Usable eye relief (measured from rim of eyecup): 15 mm
RFOV:  7.5  degrees = 131 m
AFOV (measured, rounded): 52.5 degrees
Minimum focus distance (measured): 5.5 m
Focus type:  IF
Range of individual diopter adjustment on each tube: +/- 7 dpt
Prism system:  Schmidt-Pechan
Waterproof: yes
Weight (measured, with eyepiece cover and strap): 936 g
Made in: Germany



This is the civil version of the main military binocular 7×40 EDF (“Einheits-Doppelfernrohr”) of the East German army (“NVA, Nationale Volks – Armee”), made in 1985. Produced to military specifications, it is extremely sturdy. The image has a characteristic yellow tint; Holger Merlitz explains in his book (2nd ed., page 177) that this is due to the use of special optical glass that is resistant to radiation. This is achieved by adding ceroxides to the glass; the EDF was tested with a dose of about 10’000 Röntgen/hour for a period of 10 hours (40 times the lethal dose for humans) and had to keep at least 50% of its transmission. A positive side-effect of the yellow tint: thanks to the higher absorption in the short wave part of the spectrum, contrast is slightly enhanced in misty or foggy weather. – Until very recently, basically the same binocular without the yellow tint could still be purchased from Docter /Noblex (see separate post about Docter 7×40 B/GA,×40-b-ga/), but according to news reports, Noblex is closing its binocular production in October 2020.

For detailed information about the design and history, see John Robert‘s excellent research at×40-roof-prism-binoculars.387041/



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