When we talk about the objective lens of binoculars, we mean the front lens. The front lens is the foremost lens of the objective.
The larger the lens diameter, the more light can be absorbed by the lens of the optical system. Glass purity plays a major role.
The eyepiece is the lens group of an optical system that faces the eye. The eyepieces consist of several separate lenses - achromats (3-6 individual lenses).
In addition to the coating of optics, the glass quality or type of glass is one of the most important quality factors for binoculars and riflescopes
The magnification of a binocular model is perhaps the most misunderstood feature. High magnification can be useful!
If light hits a glass-air surface (e.g. with a roof prism), the reflection causes a loss of light.
