Binoculars review

William Optics 10x50 ED

William Optics 10x50 ED
7 September 2010
At the beginning of 2006 William Optics, a Taiwanese company, launched a 7x50 ED set of binoculars, equipped with one low-dispersion glass element objective lenses. The binoculars look like Fujinon FMTR-SX products, renowned for their excellent optical and mechanical quality. William Optics also announced expanding its offer by a 10x50 model and they did it in fact, immediately.

The WO 10x50 ED is equipped with huge BaK-4 prisms and a very solid casing - these features entail big dimensions and weight. The instrument features also an individual focusing system.

  • Lornetka William Optics 10x50 ED
  • Lornetka William Optics 10x50 ED
  • Lornetka William Optics 10x50 ED
  • Lornetka William Optics 10x50 ED
Manufacturer data


William Optics
web site

Distribution / Sales:

Delta Optical
web site

Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
10 50 114/1000(6.5o) BaK-4/Porro 19 mm 1600 g 1349 PLN
Results of the review
Real front lens diameter Left:   50.05+/- 0.06 mm
Right:  50.13+/- 0.08 mm
8 / 8.0 pkt
Real magnification 9.89+/- 0.2x 3/3.0
Transmission 93+/- 3% 20.5/25.0
Chromatic aberration Low in the centre, on low/medium borderline at the edge. 7.4/10.0
Astigmatism Low. Images of stars are almost point-like. 7.4/10.0
Distortion The distance of the first curved line from the field centre compared to the field of view radius: 33% +\- 5% 3/10.0
Coma Negligible. It appears late and is low even at the very edge of the field. 8.3/10.0
Blurring at the edge of the FOV The blur occurs in the distance of 77% +\- 6% from the field of view centre. 5/10.0
Darkening at the edge the FOV Slight but noticeable. 3.9/5.0
Whiteness of the image Very good. Minimal hue of cream yellow. 4.6/5.0
Collimation Perfect. 5/5.0
Internal reflections
Left: Right:
William Optics 10x50 ED - Internal reflections - Left William Optics 10x50 ED - Internal reflections - Right
Noticeable but low.
Housing Very solid and heavy. Comfortable to hold in big hands – it is certainly not a women’s instrument. Eyecups not especially comfortable. Objective lenses’ covers on thin straps. 7.2/8.0
Focusing Individual, very solid. Move very heavily. 4.4/5.0
Tripod There is a comfortable exit. 3/3.0
Interpupilary distance from 57.3 to 74.3mm 5/6.0
Closest focusing distance 8.0 m. 0/2.0
Eyepieces FOV Apparent field of view of 63.9 deg (according to simple formula) and 58.3 deg (according to tangent formula). 13/20.0
Field of view Measured by us amounted to 6.46 +\- 0.03 degrees and it was just by 0.06 degrees narrower than given in the specifications. A quite wide field of view for this equipment class. 6/8.0
Quality of the interior of the barrels Dark, clean and matt. Black but slightly shiny screw next to the prisms. Glue is black and matt! 4.7/5.0
Left: Right:
William Optics 10x50 ED - Vignetting - Left William Optics 10x50 ED - Vignetting - Right
OL: 1.6%, OP: 1.9%
Small elements in the pupil’s area.
Prisms quality Huge, high quality BaK-4 prisms. 8/8.0
Antireflection coatings High quality MC everywhere. Greenish-blue on objective lenses, green on the prisms, green-purple-yellow on eyepieces. Medium intensity. 4.5/5.0
Warranty [years] 1 1/6.0
Final result
142.9 / 190 pkt
Econo result 0pkt.


  • huge, in fact armoured casing giving an impression of indestructible,
  • good blackening and cleanliness inside,
  • very low coma,
  • low astigmatism,
  • good whiteness rendition,
  • chromatic aberration well controlled although you could demand more from ED glass,
  • very high class of prisms and antireflection coatings,

  • very heavy,
  • big minimum focus distance,
  • just one year of guarantee,
  • visible distortion,

Another interesting pair of binoculars, which didn’t take part in our 10x50 binoculars’ test because it was simply not available on the market. It is yet another instrument about which my feelings are mixed. Its score on the absolute scale, amounting to almost 129 points out of 170, is undoubtedly praiseworthy, especially if you take into account the fact that this set of binoculars costs just 300 USD. It’s enough to glance at our binoculars’ ranking, which is generated systematically, to see that the WO 10X50 occupies the fifth place and is the cheapest device in the first fives group at the same time. Such a high position is due to its outstanding build quality and good optical properties.

On the other hand, though, it is worth noticing that the Fujinon 10x50 FMTR-SX so the binoculars the WO 10X50 ED has been modelled after, fares much better in that ranking. What’s more, the Fujinon is able to win with the WO even without ED glass in its objective lenses. You can draw an obvious conclusion that not only objective lenses are responsible for the quality of images. In 10x50 instruments, equipped with wide angle eyepieces which had an apparent field at the level of 65 degrees, exactly these parts determine the image quality at the edge of the field; in that place many aberrations, like chromatic aberration, coma, astigmatism, vignetting or distortion, make themselves felt. It can be clearly seen that the build quality of the Fujinon’s wide angle eyepieces is definitely higher than that of the WO so practically in all optical categories the Fujinon fares more or less distinctly better, achieving the final score by 14 points higher than that of the WO.

For the same reason we are not surprised that the WO 7x50 ED model, tested not so long ago, performed very well. The constructors didn’t have to use wide angle eyepieces there so they manage their job better as a result.

The WO 10x50 ED has several flaws and you must count its significant weight, short guarantee period, distinct distortion, chromatic aberration, too high for ED glass, big minimum focus distance or slightly truncated exit pupils among them. It is worth remembering, though, that these disadvantages aren’t very serious and the tested binoculars’ result puts it on a higher position than as praised instruments as the Minolta Activa and the Nikon Action EX. We can turn a blind eye to its defeat at the hands of the Fujinon because, after all, the WO costs two times less.