Nikon Action 8x40 Brochure page 4

Performance factors
Nikon offers an extensive lineup of binoculars — including several of
the world's most popular series — for a diverse range of applications.
Each model features various technical specifications that can help you
in making the right selection. Magnification is usually considered most
important, but field of view, brightness, ease of handling (weight, feel,
ergonomics), suitability for eyeglass wearers and overall construction
should also be taken into account.
Magnification
Magnification, represented by a numerical value, is the relationship between a subject's
actual proportions and its magnified size. With 7x magnification, for example, a subject
700 metres distant appears as it would when viewed from 100 metres with the naked
eye. As a rule, magnifications of 6x to 10x are recommended for handheld outdoor use.
With magnifications of 12x or greater, any shaking by hand movement is more likely to
create an unstable image and uncomfortable viewing.
field of view
All binoculars use number codes to designate various specifications. In "8x40 8.8°", for
example, "8.8°" represents the real field of view, which is the angle of the viewing field
measured from the central point of the objective lens. The apparent field of view, on the
other hand, conveys how wide that field of view appears to the naked eye. The real field
of view at 1,000 metres listed in the specifications is the width of the visible area at a
distance of 1,000 metres.
1,000m
125m
154m 8x binoculars
Apparent field of view Real field of view
* Nikon has adopted a calculation method based on ISO 14132-1:2002, and therefore,
values for the apparent field of view have changed from those previously stated. For
details, see page 44.
Binocular basics
Objective lens diameter
The objective lens diameter, combined with the quality of lens and prism coatings,
determines the amount of light gathered to form an image. If you are regularly observing
in poor light conditions, such as early dawn or dusk, or in forested areas, you may need a
larger objective lens. But large-diameter objective lenses make binoculars heavier, so
50mm is the general limit for handheld use.
exit pupil
The exit pupil is the image formed by the eyepiece lenses. The diameter of the exit pupil
(in mm) is the effective aperture divided by the magnification. The diameter of the human
eye pupil varies from 2-3mm in daylight to 7mm in the dark. An exit pupil of 7mm gives
maximum light to the dilated eye and is ideal for use in the twilight and at night.
10mm pupil diameter of the binoculars and
Diameter of exit pupil
7mm pupil diameter of a human eye
10mm
Brightness
The relative brightness value is obtained by squaring the diameter of the exit pupil. The
greater the relative brightness, the brighter the image will be. However, this value does
not correspond exactly to increases in brightness viewed with the naked eye because
light coming through the binoculars is 100% effective only if the exit pupil is the same
diameter as the pupil of the eye.
in daylight in darkness
Exit pupil diameter: 2.9mm
Exit pupil diameter: 2.9mm
Pupil diameter of human eye: 2 to 3mm
Pupil diameter of human eye: 7mm
Exit pupil diameter: 7.1mm
Pupil diameter of human eye: 7mm
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How to read the numerical information code for
binoculars
All Nikon binoculars are designated with a numerical formula, such as "10x25 5.4°".
The value "10x" indicates the magnification of the binoculars. If a person uses 10x
binoculars to observe a wild bird from a distance of 100 metres, for example, it will
appear to the observer as if he or she were viewing the bird from a distance of 10
metres (100 divided by 10 equals 10) with the naked eye.
The next number, "25", tells you that the effective diameter of the objective lens is
25mm. The greater the diameter of the objective lens, the brighter your image will
be with the same illumination. (Nikon's superior lens coatings also play a vital role in
improving lens brightness.) If the objective lens is too large, however, the binoculars
will be heavy and may cause trembling of the hands.
Finally, the number "5.4°" represents the real field of view of the binoculars. This is
the angle of the visible field, as measured from the centre of the objective lenses.
The bigger the value, the easier it is to locate an object.
Understanding the meaning of these numbers should provide you with greater
7mm freedom in selecting and using binoculars.
Check the letters in the name of any Nikon binoculars —
they convey helpful information about each model.
Individual focusing
Magnification (10x)
10x50IF HP WP
Objective diameter (mm) High eyepoint
The following icons indicate the purpose for which each
series is best suited:
Mountaineering, camping, hiking
Rugged outdoor activities demand portability and durability. Models that also feature
rubber armouring and waterproofing are ideal when you're up against the elements.
Birdwatching, nature watching
Binoculars with a wide field of view and 7x to 10x magnification are suited for general
nature viewing. Observing whales or birds at a greater distance is more comfortable
with 8x to 12x magnification models. For even closer views, Fieldscopes and Spotting
Scopes are recommended.
Marine sports, fishing
Waterproofing and durability are essential for these activities. Enhanced brightness
and a wide field of view are desirable, too. Models that feature vibration reduction are
favoured for on-board use.
Spectator sports
Binoculars that feature a wide field of view and 7x to 10x magnification are handy for
fast-moving sports. Zoom-type binoculars are convenient, too, enabling quick and easy
changes in magnification to suit the viewing situation.
Hunting and outdoors
Models with 8x to 10x magnification are preferred for hunting, with waterproofing and
durability being further prerequisites. For early morning and evening use, binoculars
with a large objective diameter and Nikon's multicoated lenses are recommended.
Travelling
Compact, lightweight models with midrange magnification and field of view are ideal
for travelling.
Theatre
Compact models with magnification of 4x to 8x are recommended for theatre and
Waterproof
concert use. To focus on a particular performer, 7x to 10x models are more appropriate.
Stargazing
Astronomical observation requires a bright optical system with a large objective
D: Roof (Dach) prism
WP: Waterproof diameter and exit pupil. Waterproof and aberration-corrected binoculars are preferred.
CF: Central focusing
IF: Individual focusing
Museum
HP: High eyepoint
In museums, compact, lightweight models with low magnification and a close focusing
distance of less than 2m are recommended.
for eyeglass wearers
Choose a high-eyepoint design so that eyeglass wearers can also enjoy a full, clear
field of view.
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