Nikon 10x25HG L DCF Brochure - Page 4

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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

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

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.