Binoculars, field glasses or binocular telescopes are a pair of identical or mirror-symmetricaltelescopes mounted side-by-side and aligned to point accurately in the same direction,allowing the viewer to use both eyes (binocular vision) when viewing distant objects. Mostare sized to be held using both hands, although sizes vary widely from opera glasses to largepedestal mounted military models. Many different abbreviations are used for binoculars,including glasses, nocks, oculars, binos and bins.Unlike a (monocular) telescope, binoculars give users a three-dimensional image: for nearerobjects the two views, presented to each of the viewers eyes from slightly differentviewpoints, produce a merged view with an impression of depth.Binoculars to be used to view objects that are not at a fixed distance must have a focusingarrangement which changes the distance between ocular and objective lenses. Traditionally,two different arrangements have been used to provide focus. Binoculars with "independentfocus" require the two telescopes to be focused independently by adjusting each eyepiece.Binoculars designed for heavy field use, such as military applications, traditionally have usedindependent focusing. Because general users find it more convenient to focus both tubeswith one adjustment action, a second type of binoculars incorporates "central focusing",which involves rotation of a central focusing wheel to adjust both tubes together. Inaddition, one of the two eyepieces can be further adjusted to compensate for differencesbetween the viewers eyes (usually by rotating the eyepiece in its mount). Because the focalchange effected by the adjustable eyepiece can be measured in the customary unit ofrefractive power, the diopter, the adjustable eyepiece itself is often called a "diopter". Oncethis adjustment has been made for a given viewer, the binoculars can be refocused on anobject at a different distance by using the focusing wheel to move both tubes togetherwithout eyepiece readjustment. Most modern binoculars are also adjustable via a hingedconstruction that enables the distance between the two telescope halves to be adjusted toaccommodate viewers with different eye separation. Most are optimized for theinterpupillary distance (typically 56mm) for adults.There are "focus-free" or "fixed-focus" binoculars that have no focusing mechanism. Theyare designed to have a fixed depth of field from a relatively close distance to infinity, havinga large hyper focal distance. These are considered to be compromise designs, suited forconvenience, but not well suited for work that falls outside their designed range.Some binoculars have adjustable magnification, zoom binoculars, intended to give the userthe flexibility of having a single pair of binoculars with a wide range of magnifications,usually by moving a "zoom" lever. This is accomplished by a complex series of adjustinglenses similar to a zoom camera lens. These designs are noted to be a compromise and evena gimmick since they add bulk, complexity and fragility to the binocular. The complex opticalpath also leads to a narrow field of view and a large drop in brightness at high zoom. Modelsalso have to match the magnification for both eyes throughout the zoom range and holdcollimation to avoid eye strain and fatigue.Night glasses are telescopes or binoculars with a large diameter objective. Large lenses cangather and concentrate light, thus intensifying light with purely optical means and enablingthe user to see better in the dark than with the naked eye alone. Often night glasses also
have a fairly large exit pupil of 7 mm or more to let all gathered light into the users eye.However, many people cant take advantage of this because of the limited dilation of thehuman pupil. To overcome this, soldiers were sometimes issued atropine eye drops to dilatepupils. Before the introduction of image intensifiers, night glasses were the only method ofnight vision, and thus were widely utilized, especially at sea. Second World War era nightglasses usually had a lens diameter of 56 mm or more with magnification of seven or eight.Major drawbacks of night glasses are their large size and weight.Digital camera binoculars are binoculars with digital camera capabilities. In these, the digitalbinocular camera is situated on top and takes a photograph or a video of the view that isseen through the binoculars. There is an LCD screen, either flat or flip-up, which allows theusers to frame the picture or video to be taken and review it afterward; the flip-up version isgenerally the more convenient one.Given the differences between the human eye and the camera lens, it is necessary to keep inmind that the photographed or recorded view may not be exactly as the one seen throughthe digital camera binocular eye-piece. The photo and video quality depends on how basicor advanced the digital camera binoculars are, specifically on what the magnification is aswell as the size of the lens. These two factors are indicated by the binocular numbers, forinstance 8 by 42, where 8 is the magnification and 42 is the lens size. The larger the lens size,the better the image. In advanced digital camera binoculars, the binocular numbers are largeand the photographs taken are good enough to be printed out.Many binoculars with digital cameras only have limited storage space on their internalmemory. Once this memory gets full, if the digital camera binocular is to be used again, thephotographs and videos taken have to be either deleted or transferred elsewhere. They canbe downloaded onto a computer or stored on memory cards or on external memory drives.In some cases, they can even be directly emailed or sent to an online photo site.Usually, all digital camera binoculars come with image manipulation software that allowsusers to re-size and adjust the downloaded photographs. Other general accessories caninclude AAA batteries, USB cable, neck strap and tripod mounts. The last is particularlyuseful for avoiding the pitfalls of handheld tremors in photographs and videos. Some digitalcamera binoculars models have fold-down rubber eye-cups to make viewing easier forpeople who wear glasses.Binoculars with digital camera are popular with hikers, bird-watchers, nature researchersand sports enthusiasts, among others. The basic, inexpensive digital camera binoculars,however, are not well-suited for any in-depth observation. For serious study, it is necessaryto get the advanced digital camera binocular models that come with special close-focus andmagnification capabilities. Bird-watchers can train such models on birds, zoom in, andcapture specific bird behaviors instantly. Sports enthusiasts too can follow the action closelyand preserve the memorable moments.
Be it a concert, the Kentucky Derby, a political rally, football game or the opera, binocularscan come in handy for just about any occasion where getting a closer view of an event isneeded. For these kinds of events, compact binoculars are ideal – small, robust, anddesigned to fit into a handbag or jacket pocket. Compact binoculars are unobtrusive andlow-key, and do not need to be as robust or specialized as their hunting, birding or marinecousins - although the basic principles behind them remain the same.Like every other pair of binoculars, spectator binoculars consist of two identical, mirror-symmetrical telescopes placed side-by-side and aligned together. This arrangement grantsobservers an incredible depth of field and magnification while retaining the eye’s ability tosee objects in three dimensions, something which a monocular telescope is unable to do.For most people, a pair of wide angle compact binoculars with magnifications levels thatrange from 6x to 7x and objective lens sizes ranging from 25mm to 40mm should suffice.Binoculars in this size range are normally lightweight, stable and easy to hold over longperiods of time. If you know you are likely to be seated, a set of binoculars with amagnification of 10x will provide a crisp, close-up image of what you are trying to view. Trynot to go above 10x, as it will cause the image to suffer.As you become more advanced and familiar with the use and handling of compactbinoculars you can begin to worry about things like magnification compared to objectivelens size. Objective lens size is a fairly simple choice to make - the larger the lens, the morelight will be collected and the sharper the final image will be. However, large lenses alsotends to lead to bulkier construction, and can be less manageable.The best advice when buying compact binoculars is to use your own common sense andjudgment – how far away will you be from the stage or whatever you plan to look at? In astandard concert hall, 10 x magnifications will probably be overkill. But if you were stood atthe back of the crowd at, say, President Osamas inauguration, then you may need the boostto the viewing distance that a larger pair of binoculars can provide. If you pick a fairly mid-powered pair of compact binoculars, the chances are that they will serve you well enough inany given day-to-day situation.Image-stabilized binoculars are binoculars that have a mechanism for decreasing theapparent motion of the view due to binocular movement.Image stabilized binoculars are designed to minimize image shaking in hand-held binoculars.Higher power binoculars bring the image closer, but the image shift is also greater with evensmaller movement of your hands. Image stabilization technology in binoculars ensuresinstant adjustment of the image to compensate for the motion. Major brands making imagestabilized binoculars include are Canon, Fujinon, Nikon, Carl Zeiss, and Bushnell.Several different mechanisms have been used for image stabilization.Binoculars with digital camera are the in thing as they can be used to take good pictures ofthe objects that you are viewing. This helps as that will mean that you have the best of theboth the worlds. You get a good pair of binoculars as well you can have the best of the
pictures of the view that you were enjoying. That said there a few things that you need lookfor the digital camera binoculars so that you derive the maximum benefit. Digital camera binoculars have the optical zoom as well as the interpolation zoom. Theinterpolation zoom is kind of a hypothetical zoom which assumes the image that you will seeand then gives you the result. The other one is the optical zoom which gives the actual zoomof the binoculars and the camera that you will be able to view. Always when reading the specifications of the binoculars with the built in digital camera youcan make sure that you have the optical zoom in mind. That way you can always get thegood digital binoculars or as people call it the dig bins.Resolution of the camera is very important and that will mean that you be very careful aboutwhat the specifications say. The digital cameras with low VGA are not very good. The lowVGA implies that you have the cameras with 1 mega pixel or less. That will not be very goodfor picture quality but will be good for sending pictures via email.Ideally you should be able to take small video clips using the digital camera. That will meanthat the digital camera that comes along with binoculars should have that capability toreplay the clips. A lot of binoculars come with the instant replay feature. Those binocularswith instant replay feature are very good for seeing what you have shot and give you aninstant idea of the picture video quality. The best way to view these is to have the LCDscreen. Therefore now there are binoculars with LCD screens on them.Another feature that should be there is the tripod adaptability. Taking pictures using thetripod is a must so that you have the best of the pictures without the shakiness of the hand.Make sure that those binoculars that you buy have a magnification of 8 or more. In factmore is also not desirable as then binoculars can become heavy. Less is not desirable as thenyou will not have good image quality.Always make sure that the binoculars having a digital camera have a memory slot for an SDcard or MMC card. Most digital cameras with binoculars have the best the slot for the samebut again it is always better to make sure that it has one. Otherwise most of the inbuiltmemory is for 300 pictures approximately and then you will have to delete those or transferthose to the PC.