Pentax FB-8 8×18



Objective diameter:  18 x 9 mm (square)
Magnification:    8x
Exit pupil:     2 x 1 mm (square)
Eye relief acc. to spec.: 11 mm
Usable eye relief (estimate, measured from rim of eyecup): 9 mm
IPD:  54 – 72  mm
RFOV:    7.5 degrees =  131 m / 1000m
AFOV: 60 degrees (approx.)
Focus type:  CF (direction of rotation from close to infinity: > clockwise)
Range of diopter adjustment (estimate): +/- 5 dpt
Extra travel of focus wheel beyond infinity: more than 8 dpt
Minimum focus distance (acc. to spec.): 1.9 m
Prism system: Schmidt-Pechan
Size:   58 x 86 x 17 mm
Waterproof: no
Weight (measured, with strap):  133 g
Made in: Japan



A toy binocular with square shaped objectives and square shaped exit pupils? Allbinos, who in their revies always comment on how perfectly round the exit pupils of a tested binocular are, would walk away shocked. But, if back in the day, one of the intended uses of the instrument was watching programs on a TV-screen? The layout of objectives and eyepieces of the FB-8 in fact corresponds to the famous “16:9” ratio of early TV sets. On the other hand, the credit-card-sized  Pentax is extremely flat – it is only 17mm thick – and lightweight and therefore deserves not only the label “pocket binocular”, but rather “shirt pocket binocular”. Inside, however, everything is “grown-up”: full aluminum-alloy case, dpt adjustment +/- 4dpt, IPD up to 72 mm. The multi-coated objective lenses with 2 elements in 1 group, eyepieces with 4 elements in 3 groups, and full-fledged Schmidt-Pechan roof prisms provide a very decent field of view for this size binocular. Of course, the tiny exit pupils much restrict the amount of light reaching your eyes, and the image is rather dark, but quite usable on a bright day. There also was a 10x version of this little gadget; both versions can still be found on the second-hand markets.

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