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Binoculars review

Kowa BD 8x32 XD Prominar

Kowa BD 8x32 XD Prominar
28 August 2015
Optyczne.pl 
Kowa is a Japanese producer with a limited line-up which, nevertheless, is quite well-known on the market. Most of it consists of ornithology instruments which not so long ago were entirely produced in Japan.

Lately, though, Kowa have show several series of binoculars produced in China and the BD XD Prominar is the best of them. It features models with following parameters: 8x32, 10x32, 8x42, 10x42, 8x56, 10x56 and 12x56.


Kowa BD Prominar XD 8x32, 10x42 and 8x56.


All of these pairs of binoculars are rather small when compared to other devices in their respective class. They are equipped with Schmidt-Pechan roof prisms made of BaK-4 glass and are phase-correction coated. They also feature a highly reflective dielectric C3 coating. The producer mentions two XD elements most likely made of low dispersion glass. All air-to-glass surfaces in optical paths are supposed to be multicoated as well.

The casings of the binoculars are made of magnesium composites; they are waterproof (but not submersible) and nitrogen-filled.

Buyers get objective cups, a joined eyepiece cup (rainguard), a strap and a hard case in the box. All products come with a 10-year guarantee of the producer.

Pictures
  • Lornetka Kowa BD 8x32 XD Prominar
  • Lornetka Kowa BD 8x32 XD Prominar
  • Lornetka Kowa BD 8x32 XD Prominar
  • Lornetka Kowa BD 8x32 XD Prominar
Manufacturer data

Manufacturer:

Kowa
web site

Distribution / Sales:

Ecotone
web site

Magnification Lens diameter Angular field of view Prisms Eye relief Weight Price
8 32 131/1000(7.5o) BaK-4/roof 17 mm 560 g 1289 PLN
Results of the review
Real front lens diameter Left:   31.92+/- 0.05 mm
Right:  31.93+/- 0.05 mm
8 / 8.0 pkt
Real magnification 7.9+/- 0.1x 3/3.0
Transmission 82.2+/- 1% 10/15.0
Chromatic aberration Almost imperceptible in the centre, a bit lower than medium on the edge. 7.8/10.0
Astigmatism Low. 8.1/10.0
Distortion The distance between the first curved line and the field centre compared to the field of view radius: 66% ± 4% 8/10.0
Coma Appears in a distance of about 80% of the field radius and on the very edge is somewhere between low and medium level. 8.4/10.0
Blurring at the edge of the FOV The blur occurs in a distance of 91% ± 3% from the field of view centre. 8/10.0
Darkening at the edge the FOV Negligible 4.5/5.0
Whiteness of the image In the red part of the spectrum the transmission is by 7% higher than in the centre of the range. Slightly yellowish hue. 4/5.0
Collimation Perfect. 5/5.0
Internal reflections
Left: Right:
Kowa BD 8x32 XD Prominar - Internal reflections - Left Kowa BD 8x32 XD Prominar - Internal reflections - Right
Slight.
4.1/5.0
Housing Quite small for the 8x32 class. Comfortable to hold. Armour made of green, slightly rough rubber which sticks well to your hand and to the casing as well. Rubberized eyecups with 4 positions. Produced in China. 8/8.0
Focusing Huge, silver and ribbed central wheel with a working range of 580 degrees. It moves smoothly and is well-damped. Individual focusing through a ribbed ring on the right eyepiece. It moves the outer element. It’s a pity the producer didn’t copy the solution you see in the 56 mm class where you have a joystick and completely inner focusing. 4.5/5.0
Tripod There is an exit with quite comfortable access. In tests of 8x32 pairs of binoculars all devices were given here an average value of 1.5 points. A tripod exit is, after all, rarely used in this class of equipment. 1.5/3.0
Interpupilary distance from 58.7 to 72.9mm 3/6.0
Closest focusing distance 1.30 meter 2/2.0
Eyepieces FOV Apparent field of view of 56.5 degrees. 6/10.0
Field of view Measured by us amounted to 7.15 +\- 0.04 degrees and it was by 0.35 of a degree lower than stated by the producer. A typical field of view for this class of equipment. 3/8.0
Quality of the interior of the barrels Tubes blackened and matted property with a significant Mount of apertures and ribs. Dark gray bottom. Clean. 4.6/5.0
Vignetting
Left: Right:
Kowa BD 8x32 XD Prominar - Vignetting - Left Kowa BD 8x32 XD Prominar - Vignetting - Right
OL: 0.70%, OR: 0.42%
6/8.0
Prisms quality Good quality BaK-4. 8/8.0
Antireflection coatings Green- yellow on objectives and eyepieces. Greenish on the prisms. Strong reflections from the prisms. Medium intensity of the coatings. 4/5.0
Warranty [years] 10 4.5/6.0
Final result
78.8%
134 / 170 pkt
Econo result 0pkt.

Summary


Pros:
  • solid casing and very handy at the same time,
  • good correction of chromatic aberration,
  • low astigmatism,
  • negligible distortion,
  • sharp image for most of the field of vision,
  • very low brightness loss on the edge of the field,
  • good colour rendering,
  • nice area near the exit pupils,
  • sharp image already from 1.3 meters,
  • good quality BaK-4 prisms,
  • excellent blackening and cleanliness inside the tubes,
  • brilliant price/quality ratio.

Cons:
  • field of view noticeably narrower than stated in the specifications.



Let’s start with the flaws or actually one single flaw. Many Chinese producers feel producing an excellent pair of binoculars it is not enough; they want it to look truly exceptional so they overstate parameter values. We’ve criticized the otherwise pretty good Vixen New Forest and Vanguard Endeavor ED II series for the same affliction and now we have to say the same about the Kowa. Why state that the field of view amounts to 7.5 degrees when it doesn’t even reach 7.2? Just because your average customer cannot check your claim doesn’t mean they won’t know. You can read tests online nowadays; the testers don’t like it when a producer overstate such an important parameter and they dock points for such a practice.

Still, a bit better transmission and you would have a perfect instrument. The producer boasts about anti-reflection multi coatings covering all air-to-glass surfaces and C3 coatings on the prisms which are able to reflect as much as 99% of light but if you look inside the tubes there are noticeable glares from the prisms and the overall transmission in the middle of the visible spectrum reaches just a medium level of 82%. It is about 10% short of the best results in this category.


Zeiss Conquest HD 8x32 and Kowa BD 8x32 XD Prominar


Still our carping ends here; after all the Kowa BD 8x32 Prominar definitely doesn’t deserve any more criticizing. Taking into account its price the result this pair of binoculars got in our test is really impressive. It corrects well or very well all basic optical aberration, its build quality is very solid, it is properly blackened and the interior of the tubes is very clean. What’s more the exit pupils are almost round and they are positioned against a nice, dark background. If you add to that a very handy and stylish casing, very comfortable to hold, even the biggest malcontents won’t have anything to say.

I do not hesitate to say it is actually one of the best options, available on the market. If you intend to spend only around 2000-2500 PLN on a pair of binoculars it would be really difficult to find anything better. Anyway we recommend it wholeheartedly.


Attention! In this test the transmission value has been measured only for two wavelengths: 532 nm (green) and 657 nm (red) with a margin of error never exceeding 1%. Four measurements have been taken for each optical path and the results have been averaged out.