Other information such as tightness or the presence of a compass is also important. We come back to it in our"How to Choose Your Marine Twins" tip .
MAGNIFICATION
This number corresponds to the power of the binoculars. With binoculars times 7 ( x7), you see a man who is 700 meters away as if you were looking at a man 100 meters away.
LENS DIAMETER
When we talk about a pair of 7 x 50 binoculars, we saw that it grows 7 times. The second digit corresponds to the diameter of its lens (here 50 mm). The larger the diameter, the more light it lets in, the more efficient the binocular is, especially when conditions become difficult (darkness, night...).
BRIGHTNESS
This information is generally not given on the manufacturer's documentation. The brightness is the ratio between the magnification and the diameter of the lens.
Example: A pair of 7 x 50 binoculars has a brightness of 51. An 8 x 30 has a brightness of 14.1 (three times less!).
THE FIELD OF VISION
This data in meters (sometimes in degrees) is the lateral width of the observation area. The wider the field, the easier it is to locate the subject. We measure the field at 1000 meters. Mid-range binoculars have a field of 115 meters while an excellent model can reach a field of 130 meters. Of course, this"performance" increases the selling price...
LIGHT TRANSMISSION
To get to your eyes, light passes through the marine binoculars. Light transmission is the ability of optics to let this light through. The crystal (glass) that makes up the lenses tends, depending on its quality, to retain more or less light.
Basic binoculars, without any treatment, will display 70% light transmission.
The mid-range, with treated optics, let through 85% light.
The very top of the range can let 95% or even 98% of light through.
Often only the manufacturers of high-performance binoculars announce this light transmission coefficient. Others prefer not to mention this measure, which is not the advantage of their product.
THE MINIMUM FOCUSING DISTANCE
This is the shortest distance that can be observed with binoculars, where the image is still sharp.
In the navy, given the use of binoculars, this distance is little used. Fix Focus binoculars - without sharpness adjustment - are generally sharp from 20 meters. That's enough at sea
And because it's all about price, the affordable binoculars are always less bright than the high-end models, which also offer a very wide field of vision.
