Zeiss Jena Delactem 8x40
Mfr: Carl Zeiss Jena, Germany
Date: circa 1936-7 (Delactem made from 1931-43)
AFOV: ~70 degrees
TFOV: 154m at 1000m (~8.75 degrees)
Eye Relief: ~12mm
Prisms: high index?
Serial Number: 1798374
The Delactem is an early example of a wide angle binocular. It is not as often encountered as the individual focus Delactis, which was made for a longer period of time. The Delactis has much longer eyepieces, though the field of view is the same. The eyepieces on this Delactem are 15mm in diameter and look the same as those on a Dekarem from the same period.
The views through the Delactem are typical of such wide angle binoculars, with a fair amount of blurring towards the edge from astigmatism. There are also some light and prism leakages noticeable. Interestingly, my sample exhibits prism vignetting on two edges of the image (from one of the two prisms on both sides). I am not sure if this is the original design or if the prisms were replaced at some point. The optics are uncoated as is typical of the time.