Binocular Carl Zeiss Jena Telefort 12x (2)

Magnification: 12x
Aperture (objective  diameter): 30 mm
Field of view: 3.3°
Exit pupil diameter: 2.5 mm
Visible  field  of view (eyepiece FOV): 40°
The closest focusing distance: 6 m
Width: 16.6 cm
Height: 9.8 cm
Weight: 650 g
Production date: 1911.

   In 1907, Carl Zeiss radically changed the framework and the design of his binoculars, replacing "civilian" models Feldstecher 6 Fach by Telex, Feldstecher 8 Fach by Telact, Jagdglas by Silvamar and Feldstecher 12 Fach by Telefort. The new devices’ detailed characteristics were published in the 74-th volume of Carl Zeiss catalog in August 1907. The optical characteristics were significantly improved in new devices (the field of view and the objective  diameter were increased, optical aberrations were decreased), and the devices’ design was also changed: the central hinge and the “lugs” for a neck strap were not attached to binocular with the help of screws any more, they became integral with it instead, an eccentric objective alignment system appeared and its frame design was also changed, the prism covers spanned the binoculars’ carcass, and they were lubricated with a special compound at the joint points in order to improve impermeability. Moreover, the prisms inside the binoculars were no longer pressed by prism covers – they were fixed with the help of special flat springs instead. It helped increasing the device’s reliability greatly. Actually, the binoculars have survived in such appearance up to present days (see Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos, pp.399-414)
   Telefort is a “champion” among Carl Zeiss binoculars in the number of its design changes during relatively short period of its production time (from 1907/1908 to the 1920s). There were 5 binocular variants of this model:
   1st version: the one, where the lower prismatic cover and the lens frame cap are one component (starting from 1907/1908) and having the eyepieces case with the “transverse” knurling https://binocollection.com/catalog/binoculars-carl-zeiss-jena-telefort-12x.html;
   2nd version: the one with long double-ring type lens frames, covered with leather and with a short carcass (starting from 1909 and up to the beginning of 1911?) https://binocollection.com/catalog/binoculars-carl-zeiss-jena-telefort-12x-(1).html;
   3rd version: the one with short double-ring type lens frames (1911-1912);
   4th version: the one with rounded objective covers (starting from 1912-1920?)
   5th version: the higher binocular, not very similar to its predecessors, with long lens frames and eyepieces’ housings, a very rare variant that was produced for a short time in 1914.
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   The considered binocular’s specimen belongs to the 3rd version, with short double-ring type lens frames. It is a “civilian” model; similar military version is marked as D.F.12x. The binocular’s “civilian” application is proved by the central hinge fixture’s (clamp’s) small diameter (see photo), which has a hole for a knob (included to binoculars delivery kit), with the help of which the hinge could have been finally fixed depending on the observer’s interpupillary distance.  The interpupillary distances scale is indicated on the upper hinge disk.
     The binocular possesses low eyepieces, with base diameter equal to 24.5 mm and the upper prism cover width equal to 52 mm (see photo). The eyepieces have a diopter scale, the transverse (cross-shaped) knurling. The binocular’s body height (including upper prism cover) is equal to 78 mm; the height without lens frame is 67 mm. The eyepieces front lens diameter is equal to 9 mm. Compared with previous, 2nd binocular’s version, the eyecups’ shape has changed a little bit and minimum focusing distance has decreased significantly: from 13.3 m to 6 m.
   There are inscriptions “Carl Zeiss Jenna” on the left prism cover. There is also an inscription “Telefort 242183 12x” on the right prism cover. The inscription is encrusted with the help of silver alloy and is made in block letters against the background of Carl Zeiss Tessar photo lens schematic image. The prism covers are made of brass and are attached to binocular’s body with the help of three screws.
   The binocular’s coffer has features peculiar to “civilian” Carl Zeiss binocular coffers of that period (see photo).
   The binocular’s serial number is "242183" and it was manufactured in 1911 as a 600 pieces batch. It is noteworthy that this series belongs to the unknown model in Hans T.Seeger. Zeiss-Feldstecher, Handfernglaser von 1894-1919, Modelle-Merkmale-Mythos book, p. 811.
   The binocular’s model with central focusing, namely Telefortem 12x, came out around 1914.