Bresser Optics 11-50750 User Manual
Binocular / Spotting Scope ABC‘s
ACHROMAT
An Achromat is an optically glued double lens. Colour and display errors in
a single lens are largely eliminated by an achromatic lens.
A good pair of binoculars has at least one achromatic lens in its eyepiece
and in its objective lens system respectively.
AIR ACHROMAT
In Air Achromats the two lenses are separated by a small air gap. The
use of Air Achromats allows abbreviation of design length and hence very
compact binoculars.
BINOCULAR COMPASS
The BRESSER BINOCOM models are supplied with builtin compasses,
that are viewable in the fi eld of view. These types of binoculars are mainly
used for maritime navigation.
COATING
Normal optical lenses refl ect 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 (steaming a refl ection-reducing mineral layer onto them)
greatly reduces refl ection 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 fi ltered out. However, the luminous intensity of the instrument 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.
See: LUMINOUS INTENSITY, relative
COLLIMATION (double image)
This is understood to mean the parallel alignment of both halves in
binoculars. If an instrument is subjected to any major impact or dropped
(e. g. on the ground) the prisms become misaligned and the instrument is
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 will be the result if such an instrument is used
for any length of time. Such instruments should always be sent in for
repair.
DIOPTRIC COMPENSATION
In binoculars with centre wheel focussing the right eyepiece (in zoom
binoculars usually the left) can be adjusted.
This compensates for the user‘s eyesight defi ciencies. In models with
single eyepiece adjustment both eyepieces can be turned as they also
serve to adjust the focus.
ED-Apo
Against (achromatic) standard lens systems, apochromatic objectives
have signifi cant less false colour. Especially at high magnifi cations the
contrast is better and the overall image is sharper. This is managed by
special ED glass material (ED = Extra low Dispersion).
EYE DISTANCE (EYEPIECE)
The binoculars can be swivelled about the centre axis, making them
adjustable to the user‘s eye spacing.
The distance between the eyes is correctly set if the user sees a single
circular image.The eye distance is measured from the centre of the left
eyepiece lens to the centre of the right one.
EYECUPS
These connect the eyepiece and the eyes. “Twist-Up” is a special eyecup
system that can easily be adjusted to different eye relieves by a simple
twist. Thus a binocular can be easily adapted for observing with or without
glasses.
Other models have cups that can be folded down. They are connected to
the eyepiece rings.
Their functions are twofold:
a) The soft rubber reduces the pressure on the eyes during lengthy
observation.
b) They can be folded down to accommodate users with spectacles.
This shortens the distance between the eyepiece lens and the eye.
Spectacle wearers thus have the entire fi eld of vision of their
binoculars available to them.
FIELD OF VIEW
This is understood to mean the visible image at a distance of 1,000 meters
from the object being observed. It is usually given in meters.
If given as an angle, 1° = 17.5m.
An instrument with a fi eld of vision over 120 m/1,000m is called „large
fi eld“, over 140/1,000m „wide angle“.
Wide-angle instruments are particularly suitable for moving objects such
as footballs or horses.
GALILEAN BINOCULARS
Binoculars without prisms. Nowadays opera glasses are virtually the
only type made applying this principle. The user‘s field of vision is
especially wide in such instruments but magnification is restricted to
a maximum of 5x.
LUMINOUS INTENSITY (general information)
The luminous intensity (LI) quantifi es the brightness of a pair of binoculars.
Under normal circumstances a 7x50 pair (LI 51) yields much greater
intensity than 10x50 (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 older people (over 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: magnifi cation)
2
e.g. 50 : 10 = 5 x 5 = 25
This calculation disregards any features improving performance such as
BaK-4 prisms, multicoating, optical glass quality, etc. Such performance
improvements are made clear by calculating the relative luminous
intensity.
LUMINOUS INTENSITY (relative)
Relative luminous intensity is the modern expression used to signify use
of specially coated lenses and barium crown glass (BaK-4) increasing this
intensity. Our binoculars have up to 60% higher luminous intensity than
simple uncoated prism glasses.
NIGHT BINOCULARS
These are binoculars with a high geometric and relative luminous intensity
(e.g. 7x50, 8x56, 9x63, etc.)
The BRESSER 8x56 Spezial JAGD is an outstanding night instrument.
ROOF BINOCULARS
These are high quality binoculars. Precisely ground roof prisms are used
to obtain a virtually linear beam path. This means binoculars can be made
very slim and handy in size. There is no difference in quality between such
models and the standard Porro binoculars.
Typical model: 8x56 Spezial Jagd
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.
RUBBER EYEPIECE CUPS
See: EYEPIECE CUPS
SPECTACLE WEARER EYEPIECES
See: EYEPIECE CUPS
TRIPOD CONNECTION
Many binoculars have a tripod thread built-in. They can be screwed
onto a tripod using an adaptor and then guarantee a static image.
TWILIGHT OUTPUT
The twilight output number quantifi es binocular visual performance and
detail visibility.
Formula: √Lens diameter x magnifi cation
The result is to be evaluated purely mathematically and only of interest
when comparing differing types of binocular (8x30, 7x50, 10x50 etc.).
The number calculated disregards binocular performance increase due
to optical treatment, top-quality glass types and the like. See luminous
intensity
TWIST-UP
see: EYECUPS
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