Bresser NATIONAL GEOGRAPHIC 8-24x50 Mode D'emploi page 11

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
fidelity, sharpness and image distortion).
EYEPIECE FOR SPECTACLE WEARERS
An eyepiece for spectacle wearers allows for a full field 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 flatest 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 quantifies binocular visual performance and detail visibility in twilight conditions.
Formula:
√Lens diameter x magnification
The result is evaluated purely mathematically and is only of interest when comparing differing types of binocular
(e.g. 8x30, 7x50 and 10x50). The number calculated disregards binocular performance increase due to opti-
cal treatment, top-quality glass types and the like. See luminous intensity for more information.
DIOPTRIC COMPENSATION
In binoculars with centre wheel focusing, the right eyepiece (in zoom binoculars, usually the left) can be ad-
justed.
This compensates for the user's eyesight deficiencies. In models with single eyepiece adjustment, both eye-
pieces can be turned, as they also serve to adjust the focus.
RUBBER ARMOUR
Binoculars with rubber armour are advisable for rugged, professional uses. The black or olive green rubber
armour protects the instrument against splashing, dropping and impacts. The armour on our instruments has
fast colouring and is proof against sunlight.
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