Magnification is the most important factor in choosing binoculars. Magnification up to 10x is appropriate for viewing without a tripod. The views seen with magnification higher than 10x can become shaky due to the vibration caused by holding it in your hands. It will also produce a darker image and narrower field of view. The magnification of a field scope can be varied by changing the eyepiece.
Choose binoculars with the best magnification according to your need. For magnification higher than 10x, use a tripod or try to secure your position by supporting your hands.
Objective Lens Diameter:
The larger the objective lens diameter, the higher the light gathering power and resolution of the binoculars or field scope. A large objective lens results in a clear image. The binocular body becomes larger as the objective lenses become larger making it less portable.
Real Field of View:
The "Real Field of View” is expressed in the angle in which you can view without moving from your position. The wider the real field of view, the wider space you can view. Choose a model with a wide real field of view for viewing fast moving objects such as birds or sports events.
“Eye relief” is the distance between your eyes from which you can view the entire field of view through the eyepiece and the eyepiece lens surface. A design with long eye relief makes it easier for viewing even with eyeglasses. A model with long eye relief causes less strain during long observing sessions.
The size of the model with a superior optical performance generally tends to be large. Choose a model which suits your need by considering your carrying method and observing location.
Various coatings are applied on the surfaces of lens and prisms. The coating reduces the loss of light, thus it produces a bright image. The optical performance depends on the type of coating and the optical surfaces applied. PFM coating, which applies multi-layer coating on all the lenses and prisms, provides an excellent optical experience.
Fixed Magnification Zoom :
There are “fixed magnification,” which allows you to view only in one magnification and “zoom,” which allows you to vary the magnification by moving the zoom lever. The eyepieces installed in field scopes are also divided into “fixed magnification types” and “zoom types.” The zoom type, in which the magnification can be varied according to what object you are viewing, has a wide range of uses. A field of view produced by zoom types with a higher magnification is narrower and darker compared to that produced by a fixed type.
Nitrogen gas filled optics provide a waterproof design which can be used in rain or snow.Choose a waterproof binocular or field scope if you are using them in a location where your optics are likely to get wet.
“BK7” … General purpose prism material.
“BaK4” … Quality prism material which offers an excellent optical performance. No dim image appears on the edges of a viewing field.
Apparent Field of View
How wide the field of view looks when viewing through the binocular is expressed as an angle.
“Apparent Field of View” = “Real Field of View” x “Magnification”
Field at 1000m
The field range seen at 1000m without moving the binoculars is expressed in meters.
Expresses a diameter of the image of the object lens produced by the eyepiece. The larger the exit pupil, the brighter the image.“Exit Pupil” = “Objective Lens Diameter” # “Magnification”
The number obtained by squaring the exit pupil is the “brightness.” The larger the number, the brighter the image.
It is expressed as the shortest distance between the binocular and an object in focus. (It varies according to the eye vision of an individual.)
Types of Prisms
There are "Porro prism" invented by an Italian, Porro, and "Dach prism" that uses roof prism (roof = dach in German). The Porro-prism binoculars provide excellent performance but the body tends to be large. The roof-prism binoculars are more compact than Porro-prism binoculars with the same aperture size. They are designed so that the lenses and prisms are in a straight line.
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