Swift Binoculars, A GUIDE TO CHOOSING

Swift Binoculars
FIELD OF VIEW....
Field of view refers to the diameter of the area seen through the binoculars. As wide a field of view as possible is most desirable under all conditions and Swift binoculars are especially selected to provide the maximum field of view consistent with other necessary factors. It should be noted again that in line with the laws of physics, the higher the power the smaller must be the field of view and vice versa. Field of view is often expressed as an angle. Swift retractable eyecups allow eyeglass wearers a full field of view.

CENTRAL vs. INDIVIDUAL FOCUSING...
Central focusing binoculars are focused by a single knurled wheel. An adjustable right eyepiece is provided for any difference between the eyes. Because they are convenient to use, Central Focusing binoculars are in the greatest demand today.

Individual Focusing binoculars are adjusted for each eye at the eyepiece. Because they are more nearly moisture proof, simple, and sturdy in construction, military services require individual focusing on binoculars they procure. Mariners and sportsmen, who are the sole user of a binocular, focus each eyepiece on infinity and either note the setting on an eyepiece for later use or tape eyepieces in position.

ALIGNMENT...
It is important that both barrels of a binocular be optically parallel so that the image from both barrels will merge into one perfect circle; otherwise, undue strain is caused and, in extreme cases, it is impossible to resolve the two images. All Swift binoculars are very carefully checked for alignment.

CONSTRUCTION...
Consistent with strength, all Swift binoculars are manufactured of the lightest materials available and are as lightweight and compact as the optical formula and built-in ruggedness will permit. Finest quality ground and polished prisms are clamped and screwed to carefully machined recesses in bubble-free castings. Exterior surfaces are protected with multiple coats of modern, synthetic enamel or with high quality textured plastics that far outlast leather. Each instrument is dehumidified and sealed in air-conditioned, dustless, final-assembly rooms. Swift "TEM-PAC' lubricants, made to operate from-30 to 250 degrees Fahrenheit, guarantee smooth operation from tropical heat to sub-zero cold.

STEREOSCOPIC EFFECT...
Viewing an object with two eyes enables us to see around each side of an object slightly. This gives us an effect of depth which is known as stereoscopic. Because objective lenses of most prismatic binoculars are actually wider apart than the eyes of the average individual, they permit much better depth perception.

COATED LENSES AND PRISM...
All air-to-glass surfaces on most Swift binoculars are coated with Swift's own, specially formulated hard amber and/or magenta coating which practically eliminates internal glare and reflections while significantly increasing light transmission. Most objective lenses are coated with an ultra-violet inhibitor coating which effectively minimizes the effect of the sun's rays. Most prism are chamfered to absorb diffused rays, giving brighter, clearer images.

LENS SYSTEMS...
Kellner Ocular System: Three part system of lenses between the prism and eye consisting of one achromatic lens and one simple lens. This system is excellent for a standard field of view.
Erfle Ocular System: Five part system of lenses between your eye and binocular prism consisting of two achromatic lenses and a simple lens. This system affords a wide field of view.
Achromatic Lens: Two lenses of crown and flint glass cemented together to eliminate color fringes.

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