Kowa BD II XD 10x42 vs Kowa BD III XD 8x42
Quick take: The Kowa BD II XD 10x42 reaches farther (10x vs 8x); the Kowa BD III XD 8x42 has a wider field of view (429 vs 378 ft @ 1000 yds).
Field of view, to scale
Top-down view · drawn to true scale — no exaggeration
Which one to buy
Picking between these really means picking 8x or 10x, since Kowa prices both at $499 and builds both around fluorite-rich XD glass and a 5.9 ft close focus. The Kowa BD III XD 8x42 is the newer model, succeeding the BD II XD 8x42, and on paper it is the more forgiving binocular: 429 ft at 1000 yards against 378, a 5.25mm exit pupil against 4.2mm, 17.2mm of eye relief against 16.5mm, and 21.3 oz against 22.8.
The Kowa BD II XD 10x42 brings reach and a track record. Owners say its field is wider than nearly any rival 10x42, which keeps small birds easy to follow even at 10x, and they report identifying ducks and loons at distance. The compromises they name are soft, distorted edges, some off-center fringing, focus slop on some units that needed warranty repair, and twilight brightness that trails premium 10x42s, which the smaller exit pupil partly explains.
For most birders the 8x42 is the better buy at the same price: wider, brighter, lighter and newer. The BD II 10x42 makes sense on open water and for shorebirds and raptors, where its reach does work an 8x can't, and it has a locking diopter and tripod adaptability that the BD III does not.
Kowa BD II XD 10x42
For shorebirds, waterfowl and raptors at distance, where 10x reach matters, from a model owners rate for an unusually wide 10x field.
Kowa BD III XD 8x42
The better choice for most birders at the same price: wider, brighter, lighter and the newer design.
| Spec | Kowa BD II XD 10x42 | Kowa BD III XD 8x42 |
|---|---|---|
| Approx. price | ~$499 | ~$499 |
| Use case | Birding | Birding |
| Magnification | 10x | 8x |
| Objective | 42mm | 42mm |
| Exit pupil | 4.2mm | 5.25mm |
| Field of view | 378 ft @ 1000 yds | 429 ft @ 1000 yds |
| Eye relief | 16.5mm | 17.2mm |
| Close focus | 5.9 ft | 5.9 ft |
| Prism | Roof | Roof |
| Glass | ED | ED |
| Coating | Fully Multi-Coated | Fully Multi-Coated |
| Weight | 22.8 oz | 21.3 oz |
| Dimensions | 5.6 x 5.0 in | 5.3 x 5.0 in |
| Warranty | Limited Lifetime | Limited Lifetime |
Feature comparison
Kowa BD II XD 10x42
- ✓ED Glass
- ✓Phase-Corrected
- ✓Dielectric Coating
- ✓Waterproof
- ✓Fogproof
- ✗Image Stabilized
- ✓Tripod Adaptable
- ✗Magnesium Body
- ✓Locking Diopter
Kowa BD III XD 8x42
- ✓ED Glass
- ✗Phase-Corrected
- ✗Dielectric Coating
- ✓Waterproof
- ✓Fogproof
- ✗Image Stabilized
- ✗Tripod Adaptable
- ✓Magnesium Body
- ✗Locking Diopter
What birders say
Kowa BD II XD 10x42
- ✓Class-leading field of view for a 10x42 roof prism - the wide-angle design is the whole reason this model gets recommended, letting birders follow small, fast birds with ease
- ✓XD lenses with fluorite-rich ED glass deliver strong chromatic aberration control for a sub-$400 binocular
- ✓Outstanding 5.9 ft close focus makes it a legitimate dual-purpose bird-and-butterfly instrument
- ✓Bright, sharp central image - owners report identifying ducks and loons at distance and following birds in dark forest understory
- ✓Light for a full-size 10x42 at 22.8 oz with a well-made magnesium-reinforced body
- ✓Enough eye relief for most eyeglass wearers, per birder owner reports
- ✓Exceptional value: reviewers consistently frame it as delivering mid-tier performance at an entry-plus price, and one owner repurchased the identical model without hesitation
- ✓Kowa's warranty and repair service earn specific praise from owners who have used it
- ✗Edge-of-field distortion and softness are the explicit tradeoff for the huge field of view - critics note the wide view comes with visible compromises
- ✗Bench testing by a forum member flagged roof-edge diffraction artifacts and design compromises from the short focal length
- ✗Some owners have had to send units in for focus-slop repairs, pointing to inconsistent quality control
- ✗One hunting-forum user found the focus wheel uncomfortable and imprecise - handling opinions are split
- ✗Some chromatic aberration remains visible despite the XD glass, especially off-center
- ✗Made in China rather than in Kowa's Japanese factory, which surprises buyers who associate the brand with Japanese production
- ✗Not in the same brightness league as premium 10x42s in twilight conditions
- ✗Durability reports are mixed enough that some forum members recommend buying from dealers with easy return policies
Kowa BD II XD 10x42 vs Kowa BD III XD 8x42: common questions
Is the Kowa BD III XD 8x42 or the BD II XD 10x42 better for forest birding?▾
The BD III XD 8x42. Its 429 ft field and 5.25mm exit pupil beat the 10x42's 378 ft and 4.2mm, which helps in a dim understory. BD II owners do report following birds in dark forest with the 10x42, but the 8x makes it easier.
Do the Kowa BD II XD 10x42 and BD III XD 8x42 focus equally close?▾
Yes, both focus to 5.9 ft. Owners of the BD II 10x42 describe that close focus as good enough to use it as a butterfly binocular, which is rare for a 10x42 and should carry over to the 8x42 on the same figure.