• 8xMagnification: Magnification The magnification of a binocular refers to how many times larger an object appears. For example, with a 10x magnification an object 1000 yards away would appear to be only 100 yards away.
• 40 mmObject Lens Diameter: Objective Lens The objective lens is the larger of the outer lenses in your binoculars. These lenses are what gather all the light that you see; the bigger the lens the more light allowed in. A larger objective lens also tends to provide better resolution and more detail than a smaller one. The sizes range from a tiny 15mm for theater glasses to 50mm and larger for low-light and spotting binoculars.
  Tip: While larger lenses allow more light in, they also make the binoculars heavier. Consider how long you may be holding the binoculars, or if you will be using a tripod.
• 5 mmExit Pupil: Exit Pupil The size of the image as seen from the binocular's eyepiece. This is the circle of light seen in the eyepiece seen from about 10 inches away. Commonly used as a measurement of how bright the binoculars are. You can figure out the exit pupil diameter by dividing the objective lens diameter by the magnification power. 10x50mm binoculars would have a 5mm exit pupil.
  Tips: A binocular works best when the exit pupil diameter matches your eye's pupil diameter. A smaller diameter of around 2-3mm is good for binoculars for bright daytime use. Larger exit pupils of around 7mm are good for low light conditions and star gazing.
• 8.2°Angle of View: Angle of View The Angle of View is the angle between the left and right edges of the field of view from the binocular's point of view. This angle will generally get smaller with greater magnification.
  Tip: Binoculars vary, some will have a wider angle of view than others of the same magnification.
• 65.6°Apparent Angle of View: Apparent Angle of View The Apparent Angle of View is the angle of view with the binocular's magnification figured in. This is simply the angle of view multiplied by the magnification. For a 10x magnification and a 5° angle of view the Apparent would be 50°. This is directly related to the Field of View, but is often used to compare binoculars.
• 429 ft.Field of View(@1000yrds): Field of View Field of view is a measurement of the area visible at a given range. So with a pair of 8x binoculars you may be able to see an area 330 feet wide from a range of 1000 yards.
  Tip: Binoculars vary, some will have a wider field of view than others of the same magnification.
• 17 mmEye Relief: Eye Relief This is the distance that the binocular can be held from your eyes and still provide a good image. A longer eye relief is better for eyeglass wearers, as it will allow them to continue to wear their glasses while viewing.
  Tips: A longer eye relief is generally preferable, but a simple solution, though not always used, is having adjustable eye cups. These can usually make up for shorter eye relief, which is common in lower end binoculars.

• 25Brightness Index: Brightness Index This is the square of the exit pupil diameter. A 3mm exit pupil binocular would have a brightness index of 9. This is a common way to measure the brightness of a binocular.
• 16.4 ft.Minimum Focusing Distance: Minimum Focusing Distance This is the minimum distance that the binoculars can render a clear image.
  Tips: The short minimum focusing distance is nice when viewing nature, going to the museum, etc. It is not of paramount importance in buying binoculars but as with everything else, it depends on how you plan to use them.
• 5.4 in.Length: Length Length of the binoculars is measured from the objective lens to the eyepiece.
• 7.4 in.Width: Width Width of the binoculars is measured from the left side to the right side of the binocular at it's widest point.
• 2 in.Height: Height Height is measured from the bottom of the binoculars when laying down flat to the highest point on the top.
• 30.1 oz.Weight: Weight Weight is an important consideration when buying a new pair of binoculars. You should consider how long you will be holding them up to your eyes, and whether or not you intend on using a tripod. Larger objective lens binoculars will weigh more than smaller lenses. Also higher quality binoculars tend to weigh more due to higher grade materials used.
• 56-72 mm.Interpupillary Distance: Interpupillary Distance The distance between the centers of a person's pupils. Every binocular has a range of movement, by pulling the barrels inwards/outwards, to accommodate different IDs - e.g. "56-72mm" means the minimum ID is 56mm and the maximum ID is 72mm. If your ID is 54mm you will have difficulty seeing through such a binocular because the barrels will not line up with the centers of both your eyes.
  Tips: Most binoculars have an adequate interpupillary distance range for most people. However, if children will be using the binoculars often you may want a binocular with a minimum ID of around 56mm or below.

Nikon 8x40 Action Extreme Binoculars

• Very Wide Field of View
• Rugged 100% Waterproof, Fogproof Construction
• Rubber Armor for Sure Grip
• Bright, Multicoated Optics
• Turn-and-slide Click-stop Rubber Eyecups
• Good eye relief for Eyeglass Wearers
• BaK4 High Index Prisms
• Eco-Glass lenses
• includes Case and Neckstrap

Like all Action Extreme Binoculars, the 8x40 model is built on an all-metal chassis with all optical components installed in a lightweight polycarbonate shell. The Eco-Glass lens system provides bright and tremendously clear images, while the streamlined Porro prism body is rubber coated for a non-slip grip wet or dry. The unique click-stop, twist-out eyecup design delivers both long eye relief and variable eye relief to customize the binocular to your eyes with or without glasses. A mid-size all around performer, the new Action EX ATB 8x40 sports a 429 feet field of view at 1,000 yards - one of the best in the Industry for a eight-power binocular.