William Optics 10×50 ED

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Objective diameter:  50 mm
Magnification:  10x
Exit pupil: 5 mm
Eye relief (acc. to spec): 16 mm
Usable eye relief (measured from rim of eyecup): 12.5 mm
IPD:  56 – 73 mm
RFOV:  6.5  degrees = 114 m
AFOV (measured, rounded): 62 degrees
Focus type:  IF
Range of diopter adjustment (estimate): +/- 5 dpt*
Excess focus beyond infinity position (estimate): 5 dpt*
Prism system:  Porro I
Waterproof: yes
Weight (measured, with eyepiece cover and strap): 1‘538 g
Made in: China



Taiwan based company William Optics (WO) sells optical instruments (such as refractors) and accessories both for the entry level and the professional markets. They have this heavily armoured 10×50 binocular most likely made in China, possibly by KUO (?), since the dimensions and many of its features and parts are identical with e.g. the same size Lunt or APM binoculars. One notable exception is the diameter of the eyelens, which is smaller on the WO, and this leads to a bit less eye relief for the WO. The William Optics 10×50 is big and heavy,  mechanically well built and offers a good optical performance; despite it featuring ED glass, the correction of chromatic aberration remains below expectation; it is still better in this regard than the (non-ED) Lunt 10×50, but both the same size APM (which has ED glass) and Fujinon (which has not) show clearly better CA correction.


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