Comparison Nikon Action EX 12x50 CF vs Olympus 12x50 EXPS I

The diameter of the area visible through binoculars / monoculars from a distance of 1 km — in other words, the largest distance between two points at which they can be seen simultaneously from this distance. It is also called "linear field of view". Along with the angular field of view (see below), this parameter characterizes the space covered by the optics; at the same time, it describes the capabilities of a particular model more clearly than data on viewing angles. Models with magnification adjustment (see above) usually indicate the maximum field of view — at the lowest magnification and the widest angle of view. This information is often supplemented by data on the minimum value.

The angle of view provided by binoculars/monoculars and available to the eye of the observer. This parameter can be described as the angle between the lines connecting the two extreme points of the image visible in the eyepiece with the eye of the observer; in other words, this is the sector actually observed through binoculars (as opposed to the actual angular field of view described below). The greater the value of this parameter, the greater part of the observed space can be seen without turning the instrument. On the other hand, a wide field of view reduces the magnification factor (see above) — or significantly increases the cost of the device compared to more focused ones.

The section of the panorama that can be viewed through the eyepieces of binoculars. The higher the actual angular field of view, the wider the visibility of the optics. Note that the angular field of view has an inverse relationship with magnification. That is, the higher the magnification, the narrower the visibility (the smaller the real angular field of view). The actual angular field of view is calculated as follows: you need to divide the angular field of view (in degrees °) by the magnification factor. In comparison, the human eye has an angular field of view of 60 arcseconds (“). In terms of degrees, you get 150 °. Good binoculars provide a real field of view somewhere within 10 arcseconds. But it does not always make sense to chase after large indicators of the real angular field of view. The fact is that when viewing a large section of the panorama, the edges of the image receive noticeable distortion.

The smallest distance to the observed object, at which it will be clearly visible through binoculars / monoculars. All such optical instruments were initially created for observing remote objects, therefore, not all of them are able to work at short distances. When choosing a model for this parameter, one should proceed from the expected observation conditions: ideally, the minimum focus distance should not be greater than the smallest possible distance to the observed object.

The range of values in which diopter adjustment can be made (see above). If you wear glasses with diopters, but plan to look through binoculars / monoculars without them, you should choose a model whose range would correspond to the characteristics of the glasses (or at least be as close as possible to them).

The diameter of the exit pupil created by the optical system of a binocular/monocular. The exit pupil is called the projection of the front lens of the lens, built by the optics in the region of the eyepiece; this image can be observed in the form of a characteristic light circle, if you look into the eyepiece not close, but from a distance of 30 – 40 cm. The diameter of this circle is measured according to a special formula — dividing the diameter of the lens by the multiplicity (see above). For example, an 8x40 model would have a pupil diameter of 40/8=5mm. This indicator determines the overall aperture of the device and, accordingly, the image quality in low light: the larger the pupil diameter, the brighter the “picture” will be (of course, with the same quality of prisms and glasses, because they also affect the brightness). In addition, it is believed that the diameter of the exit pupil should be no less than that of the pupil of the human eye — and the size of the latter can vary. So, in daylight, the pupil in the eye has a size of 2-3 mm, and in the dark — 7-8 mm in adolescents and adults, and about 5 mm in the elderly. This point should be taken into account when choosing a model for specific conditions: after all, fast models are expensive, and it hardly makes sense to overpay for a large pupil if you need binoculars exclusively for daytime use.

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.

Coating is a special coating applied to the surface of the lens. This coating is intended to reduce light loss at the air-glass interface. Such losses inevitably arise due to the reflection of light, and the antireflective coating “turns” the reflected rays back, thus increasing the light transmission of the lens. In addition, this function reduces the amount of glare on objects visible through binoculars/monoculars. There are single-layer, full single-layer, multi-layer, full multi-layer. More details about them:

- Single layer. This marking indicates that one or more lens surfaces (but not all) have a single layer of anti-reflective coating applied to them. This is inexpensive and can be used even in entry-level optical instruments. On the other hand, it filters out a certain spectrum of light, which distorts the color rendition in the visible image - sometimes quite noticeably. In addition, in this case, on some lens surfaces there is no coating at all, which inevitably leads to glare in the field of view. Thus, single-layer coating is the simplest type and is used extremely rarely, mainly in budget models.

- Full single layer. A variation of the single-layer coating described above, in which an anti-reflective coating is present on all surfaces of the lenses (at each air-glass interface). Although this option is al...so characterized by color distortion, it is devoid of another, the most key drawback of “incomplete” enlightenment - glare in the field of view. And the mentioned color distortion is most often not critical. With all this, full single-layer coating is relatively inexpensive, which is why it is very popular in entry-level and entry-mid-level models.

- Multi-layered. A type of coating in which multiple layers of reflective coating are applied to one or more lens surfaces (but not all). The advantage of such a coating over a single-layer coating is that it uniformly transmits almost the entire visible spectrum and does not create noticeable color distortions. The absence of a coating on individual surfaces reduces the cost of the device (compared to full multi-layer coating), but it is impossible to completely get rid of glare in such a system.

- Fully multi-layered. The most advanced and effective of modern types of coating: a multilayer coating is applied to all surfaces of the lenses. This way, high brightness and clarity of the “picture” is achieved, with natural color rendition and no glare. The classic disadvantage of this option is its high cost; Accordingly, full multi-layer coating is typical mainly for high-end models.

Interpupillary distance adjustment range provided in binoculars with the corresponding function.

Recall that, ideally, the interpupillary distance of the device should correspond to the distance between the centers of the pupils of the user himself. With this calculation, it is worth choosing binoculars according to this parameter; and if the device will be used by several people, it is worth making sure that they all “fit” into the adjustment range of the selected model. However, not every person knows exactly their interpupillary distance, especially since it changes with age; and the circle of users can be indefinite — for example, if we are talking about "rolling" binoculars in the hunting industry. In such cases, it is worth proceeding from the following.

In adults of more or less standard physique, the interpupillary distance is in the range from 60 to 66 mm. Modern binoculars cover this range with a margin — even the most modest models support values from 60 to 70 mm, and in most cases the lower limit of the range lies in the region of 54 – 57 mm, and the upper one — 72 – 75 mm. This is quite enough for most adults, including those with a non-standard physique — miniature, or vice versa, large. So a wider range may come in handy only in special cases. For example, if a child will use binoculars, it is desirable that the lower adjustment limit be lower than the standard 50 – 55 mm (in some models, this limit is at the level of 38 mm, or even 34 mm).