BINOCULARS - CHOOSING THE RIGHT ONES FOR YOU
Good binoculars are a combination of image quality, good magnification, size, objective lens diameter, weight, quality and durability. You must choose a binocular that fits your needs. You must keep in mind great binoculars are rugged enough to stand up in the harshest conditions, such as extreme cold, heat, endless jarring and moisture. Remember you pay for what you get. The higher the quality binocular, the higher the price.
TERMS FOR UNDERSTANDING BINOCULARS
LIGHT TRANSMISSION—This is a test of quality of construction, quality of the coatings on the glass, and quality of the glass. Amount of light going into lens is measured and light coming out through the ocular is measured with high quality coating on all glass surfaces and having high quality construction results in the highest light transmission.
LOW LIGHT CAPABILITY—Binoculars that have 90% light transmission or higher are considered to have low light capability. For a great nighttime binocular combine a good Brightness (5-7MM) and high power (10x).
FIELD OF VIEW--It is the starting point of your view to compare the width of view at different distances—usually 1000 feet. The closer you are to the object looked at the smaller the field of view. The farther away the object is, the wider the field of view. Important if you are doing close up viewing—butterflies.
INVERSION—Your view would be upside down without these inversion systems. Lenses for rifle scopes and prisms for binoculars are used this way.
OBJECTIVES—They are the large lenses in the front of the binocular. In better quality binoculars they are a system of two or more individual lenses with different types of glass. These are used to avoid achromats (color fringes).
ALIGNMENT—The precise coordination of optical elements and mechanical.
OCULARS—Lenses closest to your eyes through which you look and focus
RESOLVING POWER or RESOLUTION—Binoculars ability to distinguish fine details. Typically, more power and bigger high-quality objective lenses provide better resolution-shapness.
COATINGS—The evaporation and baking-on of extremely thin layers pf substances onto the polished lenses and prisms of optical instruments to reduce reflections and increase light transmission.
ROOF PRISM—A roof prism binocular has prisms that are in a straight line. This allows for smaller size.
DE-ALIGNMENT—Refers to a shift of the lenses due to jarring or blows. This causes double images and is uncomfortable to use.
STABILIZED BINOCULARS—Usually come in sizes 8x20 to 20x60. Construction is with motion sensors, gyro-assist motion sensors, and full gyroscope. This construction helps eliminate motion or body movement—boat, plane, vehicle.
CENTRAL FOCUSING WHEEL—Makes it possible to focus precisely both eyepieces at the same time. Also it makes it possible to compensate for unequal vision. It does a dioptric correction through the adjustment of one eyepiece, usually the right one.
DIOPTRIC CORRECTION—This is the adjustment of the optical instrument to the varying acuity of different persons eyes.
FOCUSING—The adjustment of an optical instrument to make images at varying distances sharp and clear. 2 types of focusing—central and individual eye adjustment Both systems are good. Most manufacturers of quality binoculars make both styles. In central focusing you make 2 adjustments-one to make both eyes the same strength and the second adjustment focuses both eyes at the same time. In the individual eye adjustment you will need to adjust the right ocular to your right eye, and the left ocular to your left eye.
MAGNIFICATION—This indicates how many times larger or how much closer an object appears.When off in the distance you see an object at 100 ft thru a 10x binocular, the object appears only 10 feet away.
PORRO PRISM BINOCULARS—The prisms are off-set and the body of the binocular is ergonomic and gives optimal three-dimensional viewing. Prism glass come in 2 types. They are BAK4 and BK7. BAK4 index prism precisely transmits all of the image light from the objective lens thru the eyepiece and creates a bright image without blackout. BK7 low index prism has some blackout and poorer image quality.
EXIT PUPIL—This is the circle of light that is seen in the eyepiece. The exit pupil diameter is calculated by dividing the diameter of the objective lens by the magnification.
VARIABLE OPTICS—Zoom lens permits the continuous selection of various magnifications. However, when the objective lens diameter remains constant and additional magnification is added the exit pupil gets smaller—you’ll get loss in the quality of the picture.
FIXED FOCUS—Done in the manufacturing stages whereby cementing lenses in specific locations in the tubes to create a no-focus feature—optical depth of field.
WATERPROOF/FOGPROOF—These are binoculars that are waterproof/fogproof that can be immersed in water. Water resistant and splashproof/fogproof binoculars cannot withstand being immersed in water. Please remember that rubber coatings do NOT mean waterproof. Rubber coatings refers to a better grip, more resilience and non-denting.
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