Technical data
Binoculars FAQ
What do the numbers mean?
For example 7x42:
”7x” means that the object in view appears 7 times larger than when visualised
with the naked eye.
”42” is the size or diameter of the front (object) lens expressed in millimetres.
A larger diameter lets in more light and makes the binoculars better in poor light
conditions.
What kind of prism systems are there?
Traditional porro prism system and roof prism system.
Porro prism system binoculars let more light in, and are larger and heavier and
therefore most popular in areas like boating, where brightness is of key impor-
tance while the weight and form is not so important.
Roof prism system binoculars with their compact prism design are small and
lightweight and therefore popular for outdoor users.
Different glass qualities?
There are two types of glass quality: Bak-4 and Bk-7.
Bak-4 is extremely clean and transparent and is reportedly the best binocular
grade glass on the market. Bak-4 quality is achieved through a complicated and
time consuming manufacturing process.
Bk-7 is the standard quality for glass in binoculars. It is less expensive to
manufacture and therefore more popular for simple binoculars.
What is anti-reection coating?
Stray light inside the binoculars spoils the image.
In order to enhance the viewed image, coating is applied to the lenses and/or
prisms. It consists of a thin polarizing layer of magnesium uoride. Each layer of
stray light anti-reection coating gives a brighter and sharper image. Our paten-
ted coating system Emerald Fire eliminates as much as 99.6% of the harmful
UV- and IR-radiation.
What is exit pupil?
The exit pupil is the measure of the aperture that lets the light through to the
eye. A large exit pupil gives a bright image that works very well under poor light
conditions at for instance dawn, dusk and in shadows.
By dividing the diameter of the objective lens with the magnication of the
binoculars, the exit pupil is obtained. Binoculars of type 8x25 have an exit pupil of
3 mm (25/8 = 3), which works quite well under normal lighting conditions. Bino-
culars with 7x42 and an exit pupil of 6 mm (42/7 = 6) are good for poorer light
conditions.
What is eld of view?
Field of view is the extent of the view you have through the glasses. Field of view
is expressed at a range of 1000 meters. The greater the magnication, the nar-
rower the eld of view. Higher magnication and narrower eld of view make
binoculars harder to hold still without support.
Does the size of the binocular matter?
Compact binoculars are small and light, but have smaller and less bright lenses.
Full size binoculars allow one to see a brighter image, but are larger and heavier.
Give good thought to how you will be using the binoculars and under what condi-
tions.
What kind of water protection do I need?
If the binoculars are going to be used in rain or in a marine environment it is
wise to choose a waterproof model. The same is true if the binoculars will be
subject to signicant changes in temperature. Waterproof binoculars (prefera-
bly lled with nitrogen) keep out the surrounding air and its moisture and main-
tain a stable and dry condition inside the binoculars. This prevents condensation.
When condensation dries out, it leaves droplet marks, which remain perma-
nently inside the lenses.