Anti reflective coating
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.Prism material
Material used for prisms found in binoculars and monoculars.
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BK-7. A type of borosilicate optical glass (6LR61), a relatively inexpensive and at the same time quite functional material that provides, although not outstanding, quite acceptable image quality. Used in entry-level and mid-level models.
—BaK-4. Barium optical glass, noticeably superior to BK7 in brightness and image clarity, is however also more expensive. Accordingly, it is found mainly in the premium segment.
Interpupillary distance
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).
