Kowa BD 8x42 Binoculars Review

Kowa 8 x 42 BD Binoculars
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Price Range: (4/6) Mid-High Value Binoculars       

Ideal Uses:

General Use Rating for General Use Binoculars
Birdwatching Rating as Birdwatching Binoculars
Outdoor Sports Rating asOutdoor Sports Binoculars
Safari & Travel Rating as Safari Binoculars
General Wildlife Rating as Wildlife Observation Binoculars
Hunting Rating as Hunting Binoculars

The BD42 Series binoculars from Kowa come in 8x or 10x magnifications which they describe as "an ideal companion for bird watching or any other outdoor activity that requires a bright image and a wide field of view." I recently had the chance to test the 8x44 version and below are my findings:

Unlike many other binocular manufacturers, Kowa don't make a huge selection in regards to quality and price, rather they have decided to stay true to their ideals by focusing at the top end of the market with only two main ranges, the Genesis and the BD series of binoculars.

The main differences between the Genesis and BD is in the styling, and the absence of Kowa's Prominar XD lenses that contain extra low dispersion glass in the BD series. The full size Genesis models also have larger 44m objective lenses compared to the more standard 42mm ones found on in the BD Series.

So whilst the BD Series is Kowa's second string, sitting just behind the Genesis models, it could easily be the flagship series of many other optical brands and as such I was looking forward to testing an excellent quality binocular and judging it against the very best.

Main Highlights

  • Phase Coated Roof Prisms
  • Fully Multicoated Optics
  • Kowa's C3 Prism Coating
  • Fully Waterproof & Fogproof
  • Tripod Adaptable

The Body

The body of the binoculars is covered in a rubberized armour that give you a tough binocular that also provides a good non slip surface even in wet or damp conditions. It also helps to dampen down any sounds that may be made by knocking them against anything. For example my wedding ring can make a rather loud metallic sound if I brush it against another metal object, which could easily frighten away timid wildlife or birds.

At 730g (25.7oz), they weight is fairly light in comparison to most other full sized binoculars in their class as you can see from the list below:

These Kowa 8x42 binoculars take just under one and a half turns of the dial to go from infinity to it's near focus which is an excellent 6.5 feet (2.0m).

Most binoculars that I have tested either take only one turn or two full turns or more. The aggressive mechanism on binoculars that only take one turn to go from one extreme to the other, does make them fast to focus, but can make them hard to fine tune the focus. Whilst the low gearing on binoculars that take two turns or more mean that it does take a little longer to go from one end to the other, but they do have the advantage of a good fine focus. However the extra time taken could mean missing what you were trying to spot.

I feel that Kowa have really found the right balance here. Fine focusing was simple and accurate, whilst I could quickly go from looking at a butterfly perched on a flower right next to me to looking at a distant eagle soaring above.

The diopter control is located on the right barrel of the binoculars and is adjusted by turing the ring. On the version that I tested it was tight enough so that it should not be accidentally moved, yet not so tight as to make it difficult to adjust.

Eye-Cups & Eye Relief
The Kowa BD 8x42 binoculars have comfortable twist up eye-cups provide you with an excellent 18.3mm of eye-relief, which means that they easily make it onto my own personal list of "Long Eye Relief binoculars", and should easily be enough for most people who wear glasses and want to use their binoculars without having to remove them.

The eye-cups have 5 click stops - flush against the eyepiece, three intermediate stops or fully extended. Non-eyeglass wearers will just use the eyecups in the fully extended position, whilst eyeglass wearers can adjust them to the stop that works best for them.

Water & Fog Proof
The Kowa BD 8x42 is 100% waterproof and are filled with dry nitrogen gas which stops the optics suffering from internal fogging in adverse or weather conditions that change very rapidly. Waterproofing also has the added advantage of preventing any dust or dirt from entering the body in dry and dusty areas.

Tripod Adaptable
There is a small cover or cap on the front of the central pivoting point of theses binoculars that screws off and allows you to then screw on a binocular tripod adapter (not included) that uses the standard �-inch threading, which you can then attach to your tripod.

BD42 Series Optics

As with all my binocular reviews to get an objective opinion, I compared the view through these optics with my standard benchmark binoculars, but because I still had the Kowa 10x33 Genesis XD Binoculars with me, I was also able to also compare the view with these as well.

42mm Objective Lenses & Brightness

8x42 binoculars like these have an Exit Pupil of 5.25mm and a Twilight Factor of 18.3, suggesting that these like most full size binoculars should perform pretty well in poor light conditions. This is one of the reasons why a 7x or 8x42 is a very popular choice general wildlife observation and bird watching as many birds and larger wildlife is most active in the early mornings and late afternoons when light conditions are not at their best.

It is important to remember that whilst these figures make it possible to compare the performance of different configurations of binoculars in low light conditions, they do not take into account the quality of the prisms, lenses and their coatings. And as I have already mentioned these Kowa 8x42 BD42 binoculars feature some excellent quality optics and coatings helping to produce an image that is brighter (amongst other things) than most cheaper or inferior 8x42 binoculars.

The image produced is by these BD 8x42 binoculars from Kowa is very impressive. Comparing it to my 42mm benchmark, I would describe it as being very bright and easily beats most middle of the range 42mm binoculars. Comparing the brightness with the 10x33 Genesis is a little unfair to both as the Genesis is about twice the cost of these, has smaller 33mm objective lenses, but it does come with Kowa's Prominar XD lenses that contain extra low dispersion glass. To my eyes they were almost equal, but if I had to pick one that was brighter I'd probably just favor the BD 8x42, but the difference is so slight it is almost unnoticeable. What this does this show is just how good the Prominar XD lenses are on the Genesis as even with the smaller 33mm objective lenses they can compete with a high quality 42mm binocular. On the other hand is also shows just how good these BD42 series binoculars are in that they can compete with the Genesis which it must be said in terms of image brightness are exceptional.

Image Quality
As well as bright I thought the image produced was crystal clear and sharp. The colour reproduction and contrast is great and there was no visible colour fringing (chromatic aberration). The amount of softening of the image on the periphery of the view is extremely minimal and is as good as or better than any binocular in this class. Again comparing them to the far more expensive Kowa 10x33 Genesis XD binoculars, you can start to notice why they cost more as they have almost no softening of the image, but apart from that, the views are very similar.

Schmidt-Pechan prismSchmidt-Pechan prism
As with any binocular in this price range you would expect them to have BAK-4 prisms that are made of superior optical glass to produce clearer images, but Kowa have gone one step further in that they use the Schmidt-Pechan prism design that have both BaK4 and SK15 prisms. This prism design, like roof prisms is more compact than a porro prism binocular, but does have a few drawbacks one of which that the two prisms are separated by an air-gap and one surface of the Pechan prism does not provide total reflection. To get around this Kowa have added their own highly reflective multi-coating that they call C3 coating that they say give a reflectance of 99% or more across the entire visible spectrum.

Phase Correction
The roof prisms on these Kowa 8x42 BD binoculars have been phase coated which helps to prevent the loss of contrast and resolution. To go into a little more detail, Phase-correction coatings help to reduce the phase shift of light caused by phase differences arising from total light reflection on a roof surface! This all sounds a little complicated, but basically it just keeps the light in correct color phases and has the result of reducing the loss of image resolution to maintain high-contrast images. It is a feature that is only found on high end roof prism binoculars.

Field of View
The field of view at 1000 meters is 110 meters (330ft @ 1000yds) with a real field of view of 6.3° which is not bad, but falls short compared to some of the best. For example the Swarovski 8.5x42 EL's view is 133m wide at 1000 meters with a real field of view of 7.6° and the Swift 8.5x44 Audubon ED Binoculars have a view that is 143m wide at 1000m (8.2°).

Close Focusing Distance
At 6.5ft (2m), I would say that they have a very good minimum close focusing distance that beats most other 8x42 binoculars that I have reviewed and anything under 6ft is excellent. So whilst you probably would not choose these binoculars specifically for something like viewing butterflies, 6.5ft should be close enough for most peoples uses.

Also Included

These Genesis binoculars come with an excellent quality soft carry bag that is either leather or a very good imitation, what ever the case, it is pretty well padded on the inside. Also included is a lens cleaning cloth, some instructions and your warranty card.

Neck Strap
Whilst the humble neck strap does not usually warrant having it's own title on most of my reviews, I think that the ones that comes with the Kowa BD42 Series binoculars are that good that they are well worth bringing to your attention. They are not only very well made, but they have a thick sponge padding and at the point where it rests on your neck and are wide enough to distribute the weight over a larger area, making carrying the binoculars very comfortable. As with their top of the range Genesis models, it just another sign of quality and shows that Kowa have not forgotten the fine details and finish off their optics properly rather than it just being an afterthought.

Lens Covers
The objective and eye piece lens caps on my pair of 8x42 binoculars fitted well and should not accidentally fall off. Unlike many binoculars these days, the objective lens covers are not tethered to the barrels of the binocular. which is a slight shame, but they do contain holes making it possible for you to easily attach them to the neck strap.

Kowa BD 8x42 Comparisons

Below is a table comparing some of the main features of the Kowa 8x42 BD binoculars with one of the best 42mm binocular that money can buy the Swarovski 8.5x42 EL and the similarly priced Vanguard 8.5x45 Endeavor ED Binoculars.

  Kowa 8x42 BD Vanguard 8.5x45 Endeavor Swarovski 8.5x42 EL
Price (approx): $550 (�500) $400  
Weight: 25.7oz (730g) 27.2ozs (771g) 28.9ozs (819g)
Length: 5.7in (14.6cm) 5.1in (13cm) 6.5in (16.5cm)
Width: 5.0in (12.7cm) 6.3in (16cm) 4.8in (12.2cm)
Eye Relief: 18.3mm 20.0mm 18mm
Close Focusing Distance: 2m (6.5ft) 8.2ft 8.0ft
Field of View at 1000yds: 330ft 340ft 399ft
Exit Pupil 5.25 5.29 4.94
Twilight Factor 18.3 19.6 18.9

So as you can see all three binoculars have their strong and weak points. Strong points for the Kowa is its fairly low weight, compact size and good short focusing distance. Whilst still pretty good, compared to these two, it's field of view is it's weakest point.


Highlights include the fully multicoated optics, phase coating and Kowa's C3 coatings on the prisms that do help to produce the very bright and sharp image that is as good as any binocular that I have tested in this class.

Considering that the binoculars in the Kowa BD42 series are around half of the price of the corresponding binoculars in Kowa's Genesis XD series, I would say that these make incredible value for money. The reason I say this is because they still have many of the same quality features of the Genesis models, like fully multicoated optics, phase coating on the prisms and Kowa's C3 coatings. They don't however have Kowa's very impressive Prominar XD lenses, but as good as the XD lenses are, do they make the Genesis binoculars twice as good? I personally don't think so. Don't get me wrong, if money is no object, the Genesis would be my choice. But if you are looking for a very high spec binocular and can't quite afford the Genesis, I highly recommend the Kowa BD 8x42. It is a great binocular at an excellent price that almost anyone would be proud to own.

I like Kowa's attention to detail in supplying an excellent neck strap and very good soft case with the binoculars.

They make ideal general use binoculars that will excel in nature observation and as birdwatching binoculars. They are also great optics for hunting due to their rugged design and neutral colouring. They feel great in your hands, are fairly lightweight in comparison to other high quality full size binoculars and are well balanced.

Weak points? It is a small thing, but it would have been nicer if these 8x42 binoculars had a slightly wider field of view that would make them even more appealing to bird watchers.

I would like to thank Alpha Digital Services Limited, the UK distributors of Kowa Binoculars for providing me with these Kowa BD42 Series Binoculars to review.

Kowa 8x42 BD Binoculars

Reviewed by Jason Whitehead for Best Binocular Reviews

Best Binocular Reviews Ratings:

Body Construction Quality: 8/10 82%
Body Stats: 8/10
Optical Components Quality: 9/10
Optical Stats: 7/10
Image Quality 8/10
Extras & Attention to Detail: 9/10

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Kowa 8x42 BD Binoculars Video Review

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