A Basic Understanding Of Binoculars

A Basic Understanding Of Binoculars

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You have to have a basic understanding of binoculars before buying one. This is the purpose of this article.

Collimation: A binocular is actually two perfectly aligned telescopes and getting these two telescopes perfectly aligned has to with what is called collimation. When this is not perfect, there will be a lot of strain on your eyes while viewing, which will eventually end up in a headache.
Basic design: Porro and roof prism: There are two basic and conspicuously different types of designs. All binoculars either use porro prisms or roof prisms. Porro prisms are the traditional design where the eye pieces are off-center to the barrels. Reverse porro design is applied in compact roof prism binoculars, where the eyepieces have been made to fit a viewers eyes and the objective lenses are put close to one another. In the case of roof prisms the eyepieces are in line with the objective lenses. This design is perfect for compact and pocket binoculars
Central focusing mechanism: You focus on an object by adapting the knob/wheel between the two optical barrels (could also be a toggle switch). The focus of Auto focus binoculars have been fixed for focusing at a distance at the factory, so they do not have a central focusing mechanism.
Diopter: This is a focus knob (usually at the right eyepiece) that lets you focus one side of the binoculars separately from the other, in order to calibrate the binocular for your eyes. Some auto focus binoculars actually have a diopter for each eyepiece. Once theyve been calibrated for your eyes, no one else can use it, unless they are calibrated for the new viewer.
Magnification/power: A set of technical detail imprinted on any pair of binoculars could be something like this: 7x35, or 8x40. The first number (7, 8) is the magnification number, the power of the binoculars. The object is magnified by 7 or 8 times, which means that it appears to be 7 or 8 times closer than seen with the naked eye. Magnification has a downside as well. The more powerful a binocular, the less bright the image in dim light. Moreover, the more powerful, the more difficult it becomes to focus on an object: Even the slightest hand movement is enhanced. Some binoculars do have image stabilization which electronically reduces movement for steadier viewing, but these are very expensive. A magnification of 8x is generally regarded as ideal for general, game and bird viewing.
Objective lens: The second number (35, 40) is the diameter of the objective lens (in millimeters), i.e. the two big lenses at the front of the two barrels. It is also called the aperture of the binocular. The bigger the aperture, the more light is captured, resulting in a clearer and brighter image, which is important when used in fading light.
Field of view (FOV): Another set of technical detail which is imprinted on the binoculars, could be something like this: 400 ft. at 1000 yds. This is the field of view, the width of the view at the particular distance. In this case 400 feet at 1000 yards. It can also be designated in meters or in degree. FOV is determined primarily by eyepiece design, so its a common mistake to think that pocket binoculars, being so small as compared to ordinary sized binoculars, will have a small FOV. Magnification does have an effect as well.
The exit pupil: The exit pupil can be seen by holding the binoculars at arm's length and looking through the eyepieces. The pencil of light you see is through the exit pupil. The actual diameter of the exit pupil is computed by dividing the diameter of the front objective lens (in millimeters) by the magnification of the binocular. So, in the case of a 7x35 binoculars, the diameter of the exit pupil is 5 millimeters. The relative brightness index (RBI) is an indication of image brightness. It is computed by squaring the exit pupil. So the RBI of our example is 25 (5x5=25). A RBI of 25 or greater is considered good for use in dim light.
Eye relief: For every pair of binoculars, there is an optimal distance between your eyes and the eyepieces, which is called eye relief. If your eyes are too close to or too far from the eyepieces, you can't see the whole picture: part of it is blacked out. So, if you happen to wear eyeglasses, you have to make sure the eye relief is at least 15 mm.
Coating of lenses: The lenses of all binoculars are coated with anti-reflective coating, which is applied to enhance the quality of the image. The best coating is designated fully multi-coated. In the case of roof prism binoculars the lenses also have to be coated with phase-correcting coating.
Waterproofing: A waterproof model will not be damaged by water and will not fog up inside. It will also be better sealed against dust and dirt. Make sure the binoculars are nitrogen purged/filled.
Close focus: Focusing at a distance is no problem for any pair of binoculars; focusing at close range, however, is a totally different matter. For watching birds or butterflies you will have to look for a pair with a close focus range of less than 4 meters. Compact binoculars excel in close focus, some even as close as 1 meter.

About the Author:
Cobus Cronje has written extensively on a wide variety of subjects, including binoculars. You can get more information on Pocket binoculars and How to buy safari binoculars. You could also visit his website on Build a water feature.



Article Originally Published On: http://www.articlesnatch.com


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