National Geographic 10x42mm Single Bridge Binocular, Black
The bridge is the piece of a binocular nobody thinks about until it fails. It is the hinge joining the two barrels, and it does two jobs at once: it lets you adjust the spacing to match your eyes, and it holds both optical tubes in permanent alignment with each other. If that alignment drifts, you get eye strain, headaches and a doubled image, and no amount of focusing will fix it. A single bridge runs the full width between the barrels and is the more rigid of the two common designs.
Optics on the 10x42mm single bridge
Fully multi coated lenses are paired with BaK-4 roof prisms. Multicoating treats every air to glass surface rather than only the outer ones, which is what lifts contrast and stops bright scenes washing out to grey. BaK-4 is the higher grade prism glass and delivers cleaner edges and truer colour. The 42 millimetre aperture supplies the light gathering that makes those coatings worth having, and 10x magnification resolves detail at mid to long distances.
Eye relief of 16.9 millimetres
Eye relief is 16.9 millimetres, which is the figure spectacle wearers should be checking first. It sets how far your eye can sit from the eyepiece and still receive the full image, and anything much under about 15 millimetres means glasses wearers lose the edges of the view. Twist up eye cups adjust the distance to suit either case, and a diopter adjustment lets you correct each eye separately so both barrels are sharp at once.
Field of view and close focus
The field of view is 101 metres at 1000 metres, or 5.8 degrees. Close focus is 4.5 metres, which is nearer than most 42 millimetre binoculars manage and turns them into a usable tool for insects, garden birds and anything else within a few paces rather than only for distance work.
All weather sealing
The pair is waterproof and nitrogen purged, so the barrels are filled with dry inert gas at assembly. That is what prevents internal fogging when a warm lens meets cold air, which is the failure that ruins a dawn sitting far more often than rain does.
Full features and the complete specification table appear below.
Features
- Combination of fully multi-coated lenses and superior Bak-4 prisms creates images with excellent contrast and clarity
- 42mm aperture has ample light-gathering capability to produce bright images
- 10x magnification provides crisp details at mid to long distances
- Binoculars are waterproof and fog proof for all-weather performance
- Streamlined roof prism design with a sturdy single bridge
- 16.9mm eye relief allows eyeglass wearers to easily enjoy a full image
- Diopter adjustment lets users achieve proper focus for each eye to ensure a better observing experience
- Twist-up eye cups allow for comfortable viewing, especially for those who wear eyeglasses
Specifications
| Magnification |
10x |
| Waterproof |
Yes |
| Lens Diameter |
42mm |
| Optical Type |
Roof Bak4 |
| Coating |
Fully Multi-coated |
| Body Colour |
Black |
| FOV Degrees |
5.8 |
| FOV |
101m (@ 1,000m) |
| Close Focus |
4.5m |
| Eye Relief |
16.9mm |
| Fog Proof/Nitrogen Purged |
Yes |
| Eye Cups System |
Twist-up |
| Colour |
Black |