Bresser national geographic 10x42 wp [10/44] Binoculars abc

Binoculars ABC

MAGNIFICATION

The magniﬁ cation value always is mentioned ﬁ rst in the model name (e.g. 7x50). With a magniﬁ cation of

7x, the observed object appears one-seventh of the distance away that it really is. Zoom binoculars have an

adjustable magniﬁ cation. For example, the ampliﬁ cation can be altered between 8x and 24x magniﬁ cation

in an 8-24x50 model.

OBJECTIVE DIAMETER

The lens pointing towards the object is called the objective lens. In the model name (e.g. 7x50), the second

number stands for the objective diameter in millimeters. The objective lens diameter is an indicator of the

amount of light that can enter the binoculars.

An objective diameter of 20 mm is sufﬁ cient for observations during the day. In twilight conditions, an objec-

tive diameter of 50 mm or larger is recommended, as the lenses can gather much more of the remaining

light.

TRANSMISSION

The value of the ability to let light pass through optical systems is called transmission.

OCULAR

The ocular is on the side of a pair of binoculars pointing towards the eye and is often composed of three to

six single lenses that form an achromat. The ocular is one of the factors that determines optical quality (i.e.

color ﬁ delity, sharpness and image distortion).

EYEPIECE FOR SPECTACLE WEARERS

An eyepiece for spectacle wearers allows for a full ﬁ eld of view with and without eyeglasses. Its main aim

is the adjustment of the distance from the eye to the ocular (eye relief). When an observer sees a circular

image through the binoculars, the eye relief is set correctly. Without glasses, the optimal distance can be

adjusted by three different ways:

eyecups with a sliding mechanism, eyepieces with a twist mechanism and folding rubber eyecups. For use

by spectacle wearers, these eyecups should be folded down or brought to the ﬂ atest possible position; non-

spectacle wearers should use binoculars with eyecups in their extended positions.

BINOCULAR

Optical systems with two oculars are called binocular (hence the name binoculars).

MONOCULAR

Optical systems with one ocular are called monocular.

TWILIGHT OUTPUT

The twilight output number quantiﬁ es binocular visual performance and detail visibility in twilight conditions.

Formula:

√Lens diameter x magniﬁ cation