subject: Binoculars a short description and explanation [print this page] Binocular description, Three type of binoculars, Magnification, Objective, Coatings.
Binoculars, binos or field glasses one and the same, basically are a pair of telescopes mounted side-by-side and aligned to point in the same direction. Which allow the viewer to use both eyes (binocular vision) when viewing distant objects. They vary in size from opera glasses too large pedestal mounted military models.
Binoculars give users a perceived three-dimensional image, they produce a merged view with an impression of depth. The use of both eyes also significantly increases the perceived visual acuity (resolution), even at greater distances.
Galilean binoculars
This type of construction is still used in very cheap models and in opera glasses or theater glasses.
Prism binoculars
An improved image and higher magnification can be achieved These have a disadvantage that the image is inverted. There are different ways of correcting these disadvantages.
Porro prism
Binoculars of this type use a Porro prism in a double prism Z-shaped configuration to erect the image, wider spacing of the objectives gives a better sensation of depth.
Magnification
The first number gives you the magnification. A magnification of factor 7 produces an image as if one were 7 times closer to the object. The amount of magnification you need depends in what you will use them for. Hand-held binoculars have lower magnifications so they will be less susceptible to shaking. A larger magnification leads to a smaller field of view.
Some binoculars have built in to them a stabilizing system to overcome the shake you get with a hand held binocular.
Objective diameter
The second number is the diameter of the objective lens and determines how much light can be gathered. When magnification and quality is equal, the larger the second binocular number, the brighter the image as well as the sharper the image. An 8x40, then, will produce a brighter and sharper image than an 8x25, even though both enlarge the image an identical eight times.. This makes it more comfortable to view with an 8x40 than an 8x25.
Anti-reflective coatings
Anti-reflective coatings reduce light lost. Reducing reflection reduces lost light inside the binocular which can make the image hazy (low contrast.) Modern lens coatings consist of complex multi-layers and reflect only 0.25% or less to yield an image with maximum brightness and natural colors.
Terms used to describe coatings
* coated optics: one or more surfaces are anti-reflective coated with a single-layer coating.
* fully coated: all air-to-glass surfaces are anti-reflective coated with a single-layer coating. Plastic lenses, however, if used, may not be coated
*multi-coated: one or more surfaces have anti-reflective multi-layer coatings.
* fully multi-coated: all air-to-glass surfaces are anti-reflective multi-layer coated.
I hope I have given you some inside information on binoculars. There are many sizes, brands and different levels of quality and price. Choose a binocular that will fit the propose you will be using it, not just based on price and you will have optics that you will enjoy for many years.
