Phase correction
The presence of a
phase correction system in binoculars / monoculars. This feature enhances image quality, such as resolution and colour reproduction, and minimizes colour distortion. The need to use phase correction is due to the fact that the light waves corresponding to different colours differ in length and penetrating power, which is why they also pass through the optical system in different ways. This may cause image quality degradation. To avoid this, special coatings are used in the prisms installed in the device — they retain the original ratio of colour waves and thus provide phase correction.
Eye relief
The offset is the distance between the eyepiece lens and the exit pupil of an optical instrument (see "Exit Pupil Diameter"). Optimum image quality is achieved when the exit pupil is projected directly into the observer's eye; so from a practical point of view, offset is the distance from the eye to the eyepiece lens that provides the best visibility and does not darken the edges (vignetting). A large offset is especially important if the binoculars / monoculars are planned to be used simultaneously with glasses — because in such cases it is not possible to bring the eyepiece close to the eye.
Ergonomic eyecups
The presence of
beveled eyecups(or one eyecup, in the case of monoculars — see "Type") in the design of the device. The elongated part of the eyecup during operation is located on the outside of the eye, almost on the temple; due to this, it provides additional protection for the eye — primarily from extraneous "flare" that interferes with normal viewing of the image in the eyepiece. At the same time, such models do not go well with glasses: at best, the eyecup will have to be turned up, negating all its advantages, and in some devices this is not even possible.
Range finder
The presence of a
rangefinder in the design of binoculars / monoculars. Rangefinder, as the name implies, allows you to measure the distance to a specific object; but the specific methods of such measurement may vary. The simplest and most common variant is the reticle visible in the eyepieces; such rangefinders are inexpensive and work without batteries. On the other hand, the very procedure for using them is not very convenient, because requires knowledge of the dimensions of the object being used for measurement, as well as the ability to apply certain formulas. Active laser rangefinders are more convenient: with such a device, it is enough to point the binoculars mark at the target and press the button — the automation will do the rest. Their main disadvantage is the high price; in addition, the laser requires a power source to operate.
