The distance a binocular can be held away from the eye and still present the full field-of-view. Extended or long eye relief reduces eyestrain and is ideal for eyeglass wearers
In roof prism binoculars, the prisms overlap closely, allowing the objective lenses to line up directly with the eyepiece. The result is a slim, streamlined shape in which the lenses and prisms are in a straight line. Roof prism binoculars are less bulky and more rugged than an equivalent porror model.
In porro prism binoculars, the objective or front lens is offset from the eyepiece. Porro prism binoculars provide a greater depth perception and generally offer a wider field-of-view. Because of the simplicity of this system, some of the best values can be with a porro design.
Some binoculars are O-ring sealed and nitrogen-purged for total waterproof and fogproof protection. These modesl can withstand complete immersion in water and stay dry inside. The interior optical surfaces won't fog due to rapid temperature change or humidity.
Binoculars are often referred to by two numbers separated by an "x". For example, 8x32. The first number is the power of 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.
The second number in the formula (8x32) is the diameter of the objective front lens. The larger the objective lens, the more light that enters the binocular and the brighter the image.
Most optical prisms are made from boroscillicate (BK-7) glass or barium crown (BaK-4) glass. BaK-4 is the higher quality glass yielding brighter images and high edge-to-edge sharpness.
Lens surface coatings reduce light loss and glare due to reflection for a brighter, higher-contrast image with less eyestrain.
Types of Lens 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: All air-to-glass surfaces feature multiple layers of anti-reflective coating. Fully multi-coated optical systems deliver the brightest, highest-contrast images with the least amount of eye strain because only a very small percentage of light is lost before it reaches the viewer’s eye.
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.
Resolution, or definition, is the ability of a binocular to distinguish fine detail and retain clarity.
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).
A "fine focus" adjustment ring usually provided around one eyepiece to accommodate for vision differences between the right and left eyes.
Our exclusive, patented, hydrophobic (water-repellent) coating on which condensation from rain, fog or snow forms in much smaller droplets than on standard coatings. Smaller droplets scatter less light, which results in increased light transmission and a clearer image. Makes the binocular useful even when looking directly into the driving rain.
Found on the best roof prism binoculars, this chemical coating is applied to the prisms to enhance resolution and contrast. Would not provide an advantage on porro prism models.
ED Prime Extra-Low Dispersion glass delivers amazing color resolution and contrast, and virtually eliminates chromatic aberration and color-fringing to bring out the most distinct details possible in low-light conditions.
Trophy® XLT binoculars are made with enviro-friendly materials. That
means we use no lead in the glass lenses or prisms, no PVC in the
binocular case, no PAHs in the binocular itself and 100% recycled
paper board packaging. Now you can see the outdoors with stunning clarity, and do your part to keep it beautiful.
An anti-reflection coating process that is customized for every lens element in the optical path, in order to allow the maximum amount of light from the front glass all the way back to the eyepiece. The result? Optimum brightness and true color across the light spectrum.
As light passes through the many prisms and lenses of a roof-prism binocular, some light is usually lost along the way. Our exclusive new XTR technology – utilizing 60 layers of coatings on each prism – conserves, harnesses and optimizes the available light. XTR delivers an amazing 99.73% light transmission per lens for a combined light transmission of 90%, making the Bushnell Elite® series the brightest binocular in its class.