Binoculars review

Bynolyt Seal 10x42 BCF

Bynolyt Seal 10x42 BCF
3 January 2010
The Seal series consists of porro-prismatic binoculars with the following parameters: 8x42, 10x42 and 7x50. Their solid barrels are padded with high quality rubber and they are waterproof. BaK-4 glass was used in the prisms and all air-to-glass surfaces were covered by high quality antireflection coatings. This series’ instruments are characterized by light physical weight and a comfort eye relief.
  • Lornetka Bynolyt Seal 10x42 BCF
  • Lornetka Bynolyt Seal 10x42 BCF
  • Lornetka Bynolyt Seal 10x42 BCF
  • Lornetka Bynolyt Seal 10x42 BCF
Manufacturer data


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Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
10 42 96/1000(5.5o) BaK-4/Porro 18 mm 670 g 1090 PLN
Results of the review
Real front lens diameter Left:   41.77+/- 0.05 mm
Right:  41.85+/- 0.05 mm
7 / 8.0 pkt
Real magnification 10.05+/- 0.15x 3/3.0
Transmission 89+/- 3% 16.5/25.0
Chromatic aberration Slight. 7/10.0
Astigmatism Visible. 4.5/10.0
Distortion The distance of the first curved line from the field centre compared to the field of vision radius: 51% +- 9% 5.5/10.0
Coma Slight. 7.4/10.0
Blurring at the edge of the FOV The blur occurs in the distance of 75% +- 3% from the field of view centre. 4/10.0
Darkening at the edge the FOV Slight. 3.8/5.0
Whiteness of the image Minimal pink. Almost perfect. 4.8/5.0
Collimation Exemplary. 5/5.0
Internal reflections
Left: Right:
Bynolyt Seal 10x42 BCF - Internal reflections - Left Bynolyt Seal 10x42 BCF - Internal reflections - Right
Housing Solid and quite comfortable to hold. Slippery rubber. Regulated eyecups. Quite heavy. The bridge squelches. A lot of plastic. 6.1/8.0
Focusing Central screw moderately comfortable; it turns only at 240 degrees. A thin ring on the right eyepiece which moves the whole eyepiece. It moves smoothly and evenly. Heavy pressure applied on the eyepieces causes defocusing. 3/5.0
Tripod There is a comfortable exit. 3/3.0
Interpupilary distance from 57.6 to 72.6mm 3/6.0
Closest focusing distance 3.85 m. 0.5/2.0
Eyepieces FOV Apparent field of view of 55 deg (according to simple formula) and 51.7 deg (according to tangent formula). 7/20.0
Field of view Measured by us amounted to 5.52 +- 0.03 degrees and it was in perfect accordance with the specifications. 5/8.0
Quality of the interior of the barrels Dark, matt, black glue. Clean. 4.7/5.0
Left: Right:
Bynolyt Seal 10x42 BCF - Vignetting - Left Bynolyt Seal 10x42 BCF - Vignetting - Right
Slightly truncated pupils.
OL: 1.6%, OR: 2.8%.
Prisms quality Goog quality BaK-4. 8/8.0
Antireflection coatings Greenish everywhere. Low intensity. 5/5.0
Warranty [years] 25 5/6.0
Final result
42nd place in global rank of our 10x42 test.
126.5 / 190 pkt
Econo result 20th place in Econo rank of our 10x42 test. 4.3pkt.


  • high transmission,
  • low chromatic aberration,
  • slight coma,
  • excellent whiteness rendition,
  • high quality of prisms and coatings,
  • excellent blackening and cleanliness inside the inner barrels,
  • good warranty conditions.

  • the field of view could have been wider,
  • the border of the field should be sharper,
  • distinct flares.

Once again we have here an interesting duel between four very good and very similar sets of binoculars. In alphabetical order these are as follows: the Bynolyt Seal 10x42 BCF, the Olympus EXPS-I 10x42, the Opticron Imagic TGA WP 10x42 and the Swift Optics 962 Ultra Lite 10x42. All of them are classic Porro devices, with their dimensions very much alike. Their weight is in the 670-785 grams range, their fields of view amount to exactly 5.5 degrees and eye relief distances – from 18 to 21.5 mm. The most curious thing is that even their market prices in Poland don’t differ greatly – they range from 650 to a bit over 1000 PLN (arount 250-300 USD).

Looking at these binoculars and their parameters we see at once that their potential is great. First of all we deal here with an efficient and simple Porro construction which, for an amount of about 250-300 USD, can offer a lot. Apart from that, the limited field of view of 5.5 degrees allows us to expect no serious slip-ups at its edge.

None of these binoculars disappointed us and the Swift’s performance was just excellent with the sensational price/quality ratio. The Bynolyt and the Opticron can speak about bad luck here- if it wasn’t for the Swift we would write about them very warmly here. The Olympus’s main advantage is the lowest price, which might influence seriously the interest in this instrument. Undoubtedly all the binoculars have a lot of advantages but the Swift has them significantly more of them. As it costs almost the same or just a tad more than the rivals, the choice is really rather simple unless somebody doesn’t like its original housing and a bit heavier weight (although personally I doubt anybody would mind a difference of 20-40 grams) or will be persuaded by the attractive price of the Olympus.

If I started to get interested in a 10x42 class product only one thing about it would make me feel anxious – that field of view, amounting to only 5.5 degrees. There’s no doubt that good results of those four sets of binoculars are partially the effect of such a narrow field. Most of the 10x42 instruments have a field of view at the level of 6 degrees and we can even find models with the value of 6.5 degrees. Personally I wouldn’t accept a field of view of 5 degrees in a pair of binoculars with the magnification 10x and the 42 mm objective lens – I am not very keen on such instruments because their eyepieces’ field of view is so small that I have the impression of looking through a narrow pipe. Fortunately when we increase the field from 5 to 5.5 degrees that impression disappears and it seems that the angle of 5.5 degrees is the minimum I would be able to accept because I get a lot in return for this restriction.