The Basics about binoculars Binoculars are classified with two

The Basics about binoculars Binoculars are classified with two
The Basics about binoculars
Binoculars are classified with two numbers: 8x32, 10x40, etc. The first
refers to the magnification—how many times closer an object appears. For most
of us, seven or eight power is perfect; serious naturalists may want ten. The
second number is the diameter (in millimeters) of the front, or objective, lens.
The bigger the lens, the wider their field of view—and the more the binos weigh.
What size lenses do you need? Compact binoculars have objective
lenses in the 18-to-25-millimeter range. Midsize binoculars are 30 to 35
millimeters, great for all-around use. Full-size binos have 40-to-50- millimeter
lenses, for the brightest views.
The diopter control corrects any vision difference between your eyes.
Look at an object, close your right eye, and focus the glasses normally. Then
repeat for your right eye, using the diopter control.
To maximize light transmission, the best binoculars have coatings on both
surfaces of all their lenses. Such glasses are "fully multicoated". Better models
are also sealed against rain, and the best are nitrogen-filled to eliminate internal
fogging. Check the specs for "phase-corrected prisms"—they have a coating to
enhance contrast and color accuracy.
Some binoculars are O-ring sealed and nitrogen-purged for total waterproof and fogproof protection. These
models can withstand complete immersion in water and stay dry inside. The interior optical surfaces won’t
fog due to rapid temperature change or humidity.
Magnification (Power)
Binoculars are often referred to by two
numbers separated by an "x". For example: 8x32. The first number is the power or magnification of the
binocular. With an 8x32 binocular, the object being viewed appears to be eight times closer than you would
see it with the unaided eye.
Objective Lens Size
The second number in the formula (8x32) is the diameter of the objective or front lens. The larger the
objective lens, the more light that enters the binocular and the brighter the image.
Coated Optics
Lens surface coatings reduce light loss and glare due to reflection for a brighter, higher-contrast image with
less eyestrain.
Types of Coatings:
Coated – A single layer on at least one lens surface.
Fully Coated – A single layer on all air-to-glass surfaces.
Multi-Coated – Multiple layers on at least one lens surface.
Fully Multi-Coated – Multiple layers on all air-to-glass surfaces.
Field-of-View (F.O.V.)
The side-to-side measurement of the circular viewing field or subject area. It is defined by the width in feet or
meters of the area visible at 1000 yards or meters. A wide-angle binocular features a wide field-of-view and
is better for following action. Generally, the higher the magnification, the narrower the field-of-view.
Exit Pupil
Refers to the size of the circle of light visible at the eyepiece of a binocular. The larger the exit pupil, the
brighter the image. To determine the size, divide the objective lens diameter by the power (an 8x32 model
has an exit pupil of 4mm).
Eyeglass Wearers – Eyecups
Most binoculars come with twist-up, pop-up or soft rubber fold down eyecups which go down for eyeglass
wearers. These options allow everyone to see the entire field-of-view.
Diopter Adjustment
A "fine focus" adjustment ring usually provided around one eyepiece to accommodate for vision differences
between the right and left eyes.
Rubber Armor
Rubber armor provides multiple benefits. It helps protect the binocular from the bumps and scratches that
come with day-to-day use. It provides a comfortable gripping surface for making them easier to hold on to.
It's easy to wipe clean after a tough day in the field. And it suppresses noise if the binocular bumps
aluminum or other non-rubber surfaces, which might otherwise spook wildlife
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