Binoculars review

Fomei Diplomat 10x42 DCF

Fomei Diplomat 10x42 DCF
4 January 2010
Consisting of two models with the parameters of 8x42 and 10x42, the Diplomat series is the most expensive line of the Fomei binoculars. These instruments are produced in Japan and equipped with BaK-4 glass prisms in the roof system with special phase correction coatings. Additionally, all the optical elements in both instruments are covered by anti-reflection multi-coatings.

The light and handy casing is made of aluminum and covered by high quality rubber so the binoculars are waterproof, and nitrogen-filled.

  • Lornetka Fomei Diplomat 10x42 DCF
  • Lornetka Fomei Diplomat 10x42 DCF
  • Lornetka Fomei Diplomat 10x42 DCF
  • Lornetka Fomei Diplomat 10x42 DCF
Manufacturer data


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Distribution / Sales:

Medikon Polska Sp. z o.o.
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Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
10 42 105/1000(6o) BaK-4/roof ? mm 760 g 1650 PLN
Results of the review
Real front lens diameter Left:   41.93+/- 0.05 mm
Right:  41.95+/- 0.05 mm
8 / 8.0 pkt
Real magnification 9.96+/- 0.15x 3/3.0
Transmission 82+/- 3% 10.5/25.0
Chromatic aberration Medium in the centre, significant at the edge. 5.1/10.0
Astigmatism Well-corrected. 7.1/10.0
Distortion The distance of the first curved line from the field centre compared to the field of vision radius: 50% +- 4% 5/10.0
Coma Slight. 7.3/10.0
Blurring at the edge of the FOV The blur occurs in the distance of 84% +- 4% from the field of vision centre. 6/10.0
Darkening at the edge the FOV Slight. 3.9/5.0
Whiteness of the image Minimal cream. 4.5/5.0
Collimation Exemplary. 5/5.0
Internal reflections
Left: Right:
Fomei Diplomat 10x42 DCF - Internal reflections - Left Fomei Diplomat 10x42 DCF - Internal reflections - Right
Housing Very solid and handy . The rubber near the objectives sticks out a bit. Not regulated eyecups. 6.8/8.0
Focusing Comfortable central screw. Running through the whole focusing scale takes a 450-degree turn. Comfortable individual focusing but it moves the lens. 4.3/5.0
Tripod Moderately difficult access. 2.5/3.0
Interpupilary distance from 58.6 to 73.7mm 4/6.0
Closest focusing distance 1.7-m. 2/2.0
Eyepieces FOV Apparent field of view of 59.9 deg (according to simple formula) and 55.2 deg (according to tangent formula). 11/20.0
Field of view Measured by us amounted to 6.01 +- 0.03 degrees and it was in accordance with the specifications. 5/8.0
Quality of the interior of the barrels Dark but slightly shiny. Nice blackening of the prisms cell. Clean. 4.4/5.0
Left: Right:
Fomei Diplomat 10x42 DCF - Vignetting - Left Fomei Diplomat 10x42 DCF - Vignetting - Right
Egg-shaped pupils.
OL: 7.9%, OR: 3.6%.
Prisms quality Good BaK-4. 8/8.0
Antireflection coatings Green on the objectives and prisms. Purple-green on the eyepieces. Too high intensity. 4.5/5.0
Warranty [years] 5 3.5/6.0
Final result
36th place in global rank of our 10x42 binoculars test.
127.4 / 190 pkt
Econo result 32th place in Econo rank of our 10x42 binoculars test. -0.4pkt.


  • handy and solid casing,
  • slight coma and astigmatism,
  • good whiteness rendition,
  • sharp image almost to the very edge,
  • good blackening,
  • low flares,
  • sharp image already from 1.7 meters,
  • good quality BaK-4 prisms.

  • distinctly egg-shaped pupils,
  • distinct chromatic aberration at the edge of the field.

In the next stage of the 10x42 binoculars test five very similar instruments competed against each other. In alphabetical order these are as follows: the Bynolyt Buzzard SHR, the Ecotone AD-7, the Fomei Diplomat, the Opticron Verano and the Vixen Apex Pro. The chart below shows a comparison of properties and prices of those instruments.

As you see, the parameters of these binoculars are almost identical. All of them are small, handy and light constructions of practically the same weight and the same dimensions and identical field of view. Their exteriors don’t differ either as can be seen in the photo below.

The weight differences are so small we can suspect in every set of binoculars an identical optical system was used in the sense of the number of elements and groups. The instruments can differ slightly when it comes to the eyepieces’ construction which might be suggested by minimal differences in eye relief values, changing from 15 to 17 mm. What’s more, the binoculars have certainly different coatings which is clearly visible if you just glance at their colours and intensity.

When it comes to the score in the test the binoculars occupy exactly the same quality segment. All of them got about 123 points and the difference between the best and the worst amounts to only 2.5 points. It is really not much because 2-4 points constitute the estimated summary error of our testing methods. From the statistical point of view the score differences are practically negligible, although they lead to interesting conclusions.

Common traits of all the binoculars are quite visible. Because of small dimensions the prisms distinctly limit the light access through egg-shaped pupils. That effect is bigger for the left pupil. Short and small construction is also the source of problems with chromatic aberration correction. The eyepieces with the 60-degree-wide field of view don’t show sharp images to the very edge and about 20% of the field is visibly blurred. The binoculars’ transmission level is not impressive (apart from the Buzzard) because of the light loss on vignetting pupils and aluminum coatings on the prisms (only the Bynolyt used better SHR coatings).

It’s worth noticing that the Vixen, which is the cheapest, fared the best of these five devices. Vixen is a Japanese company after all and its factory is also situated in Japan. If you are close to the factory you can control it efficiently and cut costs at the same time.

One of the most expensive binoculars here is the Bynolyt Buzzard. The higher price can be justified by using special coatings on the prisms which enhance transmission (SHR). The test score seems to confirm it fully. In categories connected with the coatings (transmission, flares or coatings) the Bynolyt fares significantly better than the competitors although it wastes that advantage in other categories. If you consider transmission and a long guarantee period to be very important features the Bynolyt will be an excellent choice.

The next interesting suggestion is the Ecotone AD-7. Its score is the worst in this group but the price/quality ratio undoubtedly the best. Certainly it is a product worth pondering.

Perhaps the most difficult positions occupy the Fomei Diplomat and the Opticron Verano. For a really significant amount of money, compared to their rivals they offer nothing more than good guarantee conditions. When it comes to the optics and build quality their level is exactly the same as that of twice cheaper instruments from Vixen and Ecotone. Opticron Verrano is a bit lighter and it might be also a serious asset.