Binoculars

A binocular (from Latin, bi-, "two-", and oculus, "eye") is a hand-held tool used to make distant objects appear closer by passing the image through two adjacent series of lenses, and erecting prisms. The prisms revert the image by the principle of total internal reflection of the incoming light. Binoculars display images right side up instead of inverted as astronomical telescopes do. The prisms can be arranged in a dog-leg double Porro configuration, the traditional arrangement, which results in a wide set of binoculars. The objective lenses are not aligned with the eyepieces, and the prisms reflect the light along a Z-shaped path to the eyepiece. "Roof prism" binoculars (using either an Abbe-Koenig or Schmidt-Pechan design) have the objective lenses in line with the eyepieces and are therefore narrower than those which use the porro configuration. By definition, the magnified images are available to both eyes of the observer.

Current models of binoculars can be so powerful that they are better described as two small telescopes pointing in the same direction, with the two oculars arranged so that it is possible to look through them with both eyes. Most binoculars have a mechanism for changing the distance between the oculars to adapt to different users, and a dioptre adjustment is often employed on one eyepiece (usually the right) to make up for any difference in focus of the two eyes. The normal dioptre setting ranges from 56-72mm.

The optical characteristics are described by two numbers separated by "x", for example "7x50". The first number is the magnifying power, the second is the diameter of the objective lens (the one further from the eye) in millimeters.

Binoculars range from small 3x10 models, often used in theaters, to average 7x50 or 10x50 for amateur outdoor use, to large 20x80 or even 20x140 "galaxy" models. The largest models are more like telescopes, as their high magnifying power means a static mounting is necessary, otherwise natural small hand movements would be amplified and make viewing difficult. For this reason a practical limit on standard hand-held binoculars is put at 9x or 10x.

This limitation can be avoided by the use of the image-stabilized binoculars supplied by a number of manufacturers. With the use of electrical or mechanical image stabilization, binoculars up to 20x can be hand-held. The image of more moderate (8x-10x) power binoculars is also significantly improved with this technique. However, it does come with some drawbacks. In reality the images produced are usually a little bit blurrer than the best traditional models.

• Enjoy the View - Use a Binocular

Of particular interest in astronomical use is the ratio between magnifying power and objective lens diameter. Due to the way binoculars work, the resulting ratio is the diameter of the final exit pupil on the oculars. For example, a 10x50 binocular produces a 5 mm exit pupil (objective size divided by the magnifying power). For maximum efficiency, this image should match the diameter of the eye's pupil, which in dark environments grows to about 7mm. This ratio is also a measure of the brightness of the image: the larger the exit pupil, the brighter the image reaching the eye. Thus 10x50 and 8x40 binoculars have the same brightness, although the latter has a smaller magnification. An exit pupil larger than the diameter of the user's eye pupil is therefore inefficient.

Different optic types also affect relative brightness. A Porro prism binocular will produce a brighter image than a roof prism binocular of the same magnification and objective size. The quality of the glass and optical coatings will also affect the apparent brightness.However, with the advance of the phase-correction prism coating and later dielectic prism coating, the optical quality of a few premium roofies are at least on par with most premium Porro glasses. The current market trend is that, in the realm of portable binocular, roofies will dominate the market.

Binoculars have the advantage over telescopes and monoculars of the same diameter by enabling the use of both eyes at the same time, which provides a better experience for the observer, partly due to the stereoscopic effect, allowing the user to judge and follow movements more easily. It is therefore much easier to follow fast-moving objects such as aircraft, water skiers or race horses with binoculars than with a telescope.

Binoculars are widely used by amateur astronomers. Their wide field of view enabling their use in comet hunting and general observation. Larger binoculars become uncomfortable and difficult to hold steady, and are mounted on tripods or other supports. Binoculars with a very wide separation (several meters) have been used for accurate rangefinding, although modern electronic equipment has made this application redundant.

Image stabilisation
Shake can be much reduced, and higher magnifications used, with binoculars using image stabilisation technology. Parts of the instrument which change the position of the image may be held steady by powered gyroscopes or by powered mechanisms driven by gyroscopic or inertial detectors, or may be mounted in such a way as to oppose and dampen sudden movement. Stabilisation may be enabled or disabled by the user as required. These techniques allow binoculars up to 20¥ to be hand-held, and much improve the image stability of lower-power instruments. There are some disadvantages: the image may not be quite as good as the best unstabilised binoculars when tripod-mounted, and stabilised binoculars contain more advanced technology to go wrong, and to become obsolete. They are also more expensive, heavier, and battery life tends to be short. Some technologies make it difficult to move the binoculars to follow moving objects when stabilisation is enabled.

Choosing binoculars
When choosing binoculars, one should pick the best within budget. Mechanically the binoculars should be nitrogen-filled, accurately collimated and aligned, and robust. Optically all air-lens surfaces should be fully multi-coated (FMC). Roof-prism binoculars should have phase coating.
Binoculars of the same make and model may vary from unit to unit, although hopefully less so for the more highly priced models of quality manufacturers, so the experienced user may benefit from trying several samples. By the same token, many cheaper types of basically sound design may have a few exceptionally good units.

Some reputable binocular manufacturers as of 2005:
1. European Brands:
* Leica GmBH (Ultravid, Duovid, Geovid: all are Roof)
* Swarovski Optik (SLC, EL: all are Roof; Habicht: Porro, but to be discontinued)
* Zeiss GmBH (FL,Victory, Conquest: all are Roof; 7x50 BGAT/T, 15x60 BGA/T:Porro, but to be discontinued)
* Docter Optik (Nobilem: Porro)
* Optolyth (Royal: Roof; Alpin: Porro)
* Steiner (Commander, Nighthunter: Porro; Predator, Wildlife: Roof)

2. Japanese Brands:
* Canon Co. (I.S. series, Porro variants?)
* Nikon Co. (High Grade series, Monarch series,RAII, Spotter series: Roof; Prostar series, Superior E series, E series, Action EX series: Porro)
* Fujinon Co. (FMTSX, MTSX series: Porro)
* Kowa Co. (BD series: Roof)
* Pentax Co. (DCFSP/XP series; Roof, UCF series: Inverted Porro; PCFV/WP/XCF series: Porro)
* OLympus Co. (EXWPI series: Roof)
* Minolta Co. (Activa, some are Roof, some are Porro)
* Vixen Co. (Apex/Apex Pro: Roof; Ultima: Porro)
* Miyauchi Co. (Specialized in over-sized Porro binocualars)P.S. Many of them are OEM products of Kamakura or Chinese manufacturing plants.

3. Chinese Brands:
In the early years of the 21st century some mid-priced glasses have become available on the internal Chinese market. A few of them are comparable both in performance and in price to their western counterparts.
* Sicong (from Xian Stateoptics. Navigator series: Roof; Ares series: Porro)
* WDtian (from Yunnan State optics, all Porro)
* Yunnan State optics (MS series: Porro)

Naval ship binoculars
Binoculars are widely used by amateur astronomers, their wide field of view making them useful for comet and supernova seeking (giant binoculars) and general observation (portable binoculars). The major market is amongst bird watchers and hunters, who mostly prefer, and are prepared to pay for, the lighter but expensive roof-prism models.

See also
• Monocular
• Telescopes
• Spotting scope
• Opera Glasses

• double Porro prism
• tripods
• Camera Lens

• Nikon 8x42 Monarch ATB

• Zhumell 7x50 Marine with Compass and Reticle

• Zhumell Bring em Near Pirate Spyglass 25x30

• Swarovski 10x42 EL Binoculars

• Binocular Cases

• Woodland Hills Telescope Offers The New Canon 10x42 L IS Binoculars
• Binoculars are an Often Undervalued Investment

binoclar, binoular, bnocular, binoculr, bynocurals, bnoculars, binoculrs, binocuars, binoclars, binculars, bioculars, binoculasr, binoculras, binouclars, bincoulars, bionculars, bnioculars, ibnoculars, inoculars, binoculars, bynoculars, binoculals, binocuar, binocular, bynocurars, binocurals, bincular, biocular, binocualrs, binocluars,

This article is licensed under the GNU Free Documentation License.
It uses material from the Wikipedia article "Binoculars".