Bresser national geographic 8-24x50 Инструкция по эксплуатации онлайн [12/44] 151178

COLLIMATION (double image)

This term means the parallel alignment of both halves of a pair of binoculars. If an instrument is subjected to

any major impact or dropped, the prisms may become misaligned, making the instrument out of collimation.

Observation through such an instrument yields double images, as the contours seem to the observer to be

displaced.

Readjusting for eyesight can compensate minor maladjustment of this kind. However, a headache may result if

such an instrument is used for any length of time. Such instruments should always be sent in for repair.

LUMINOUS INTENSITY (general information)

The luminous intensity (LI) quantiﬁes the brightness of a pair of binoculars. Under normal circumstances, a 7x50

pair (LI 51) yields much greater intensity than a 10x50 pair (LI 25). To exploit the greater intensity of 7x50s, the

user’s pupils must be dilated to the size of the instrument’s exit pupil [EP] (in 7x50, EP = 7.14). In people over

age 50, the pupil often doesn’t fully dilate. In such cases, the higher luminosity cannot be exploited.

LUMINOUS INTENSITY (geometric)

The geometric luminous intensity is the mathematical brightness value of a pair of binoculars. Models with

higher luminous intensity are especially suited to observation at twilight.

Formula for calculating luminous intensity:

(Lens diameter / magniﬁcation)

e.g. (50/10)

= 5 x 5 = 25

This calculation disregards any features improving performance, such as BaK-4 prisms, multicoating or optical

glass quality.

FIELD OF VIEW

This is understood to mean the visible image at a distance of 1,000 metres from the object being observed. This

measurement is usually given in metres.

If given as an angle, 1° = 17.5 m.

An instrument with a ﬁeld of vision over 120 m/1,000 m is called ‘large ﬁeld’, and one with a ﬁeld of vision over

140/1,000 m is ‘wide angle’. Wide-angle instruments are particularly suitable for viewing moving objects such

as footballs or horses.

TRIPOD CONNECTION

Many binoculars have a tripod thread built in. These binoculars can be screwed onto a tripod using an adaptor,

which guarantees a static image.

COATING

Normal optical lenses reﬂect part of the light falling on them.

This causes a loss of light and a reduction in contrast due to light scatter.

Coating the lenses by steaming a reﬂection-reducing mineral layer onto them greatly reduces reﬂection and

increases light transmission (permeability).

This is a coating of 7 to 15 layers of ruby-coloured mineral steamed onto the objective lens. It increases image

contrast in sunlight, as the red spectrum is mainly ﬁltered out. However, the luminous intensity of the instru-

ment is reduced by approximately 7%. Fully coated binoculars let approximately 60% more light through than

uncoated ones. Special coatings (UV, multilayer) can be used to increase luminous intensity even further.