Basic knowledge

The fact that binoculars can be used in a wide variety of situations means that each product has its own specialties. Therefore, it is important to have a basic knowledge of the product and to know for which purpose it is used.

Magnification indicates how much larger an object appears compared to the naked eye when viewed through binoculars. For example, using 8x binoculars makes an object appear the same size as it would if viewed with the naked eye from 1/8th of the distance.

The lens located on the front side of the binoculars when you look through, is called the objective lens. The objective diameter represents the size of this lens.

Higher magnification allows you to view objects from a greater distance, but it narrows the field of view and makes the image more susceptible to hand shaking. Additionally, larger objective lenses have better light-gathering capabilities, resulting in brighter images, but they also increase the size and weight of the binoculars. Understanding these pros and cons is essential when choosing binoculars.

There isn't just one way to categorize binoculars. Understanding the distinct features of each type makes it easier to choose a product that meets your specific needs.

In order to achieve high magnification and a wide field of view, binoculars employ an optical system (Keplerian design) that uses convex lenses on both the objective lens and the eyepiece lens. This results in an upside-down image, which is then corrected using prisms. There are two types of prisms used for this purpose: Porro prisms and Dach prisms.

The CF (Center Focus) mechanism adjusts the central focus knob of the binoculars to simultaneously focus both eyes. On the other hand, the IF (Individual Focus) mechanism adjusts the focus separately with dedicated focus knobs for each eye. Since achieving waterproofing is somewhat challenging with the CF mechanism, the IF mechanism is used for waterproofing in Porro prism binoculars. IF mechanism is well-accepted for applications such as marine and astronomical observations where frequent focusing is not required. However, it is rare for IF mechanism to be used in other scenarios due to the time-consuming nature of individual focus adjustment.

FUJINON binoculars incorporate a vibration control mechanism that ensures the binoculars' vibrations do not affect the prism's alignment by employing a gimbal system for the roof prism. This mechanism provides a significantly wider range of stabilization compared to lens shift-based vibration control in digital cameras or other brands' image stabilized binoculars.

This system detects binocular vibrations electrically using gyro sensors and drives the gimbal through actuators to maintain a stable alignment. It is lightweight, offers excellent noise reduction, and can be implemented at a relatively affordable cost.

This system attaches a high-speed rotating flywheel to the gimbal to maintain a stable alignment through inertia. It provides exceptionally stable vibration reduction, although the motor and flywheel are relatively heavy and produce some noise. It is also comparatively expensive but offers superior stabilization performance.

Explanation provided at the beginning of this page, so omitted.

Explanation provided at the beginning of this page, so omitted.

It represents the range visible through binoculars in terms of the angle seen with the naked eye.

Indicates how much it can correct the difference in visual acuity between the left and right eyes.

M: Magnification, D: Objective Diameter, F: Field of View

Note that the above specifications do not consider the actual transmittance and reflectance of the lenses and prisms. Therefore, it is important to note that with the same M and D values, the brightness value will be the same for both high-end and entry-level binoculars.