Single coated binoculars and monoculars

Single layer

— this marking means that one or more surfaces of the lenses (but not all) have been coated with a single layer of anti-reflection coating. This is inexpensive and can be used even in entry-level optical devices. On the other hand, it filters out a certain spectrum of light, which distorts the colour reproduction in the visible image — sometimes quite noticeably. In addition, in this case, on some surfaces of the lenses there is no coating at all, which inevitably leads to the appearance of glare in the field of view. Thus, single-layer enlightenment is the simplest variety and is used extremely rarely, mainly in low-cost models.