Binocular parts and terminology

Binocular Parts

Focus Wheel - Used for changing the focal distance of the binocular.

Dioptre Adjuster - Used to correct any difference in "eye strength".  

Strap Loop - To connect the binocular strap (supplied) to.

Binocular Hinge - The binocular halves can be hinged to increase or decrease the distance between the two ocular lenses.  This distance is called the interpupillary distance. 

Lens Cover - Stay-on lens covers are supplied with all Hawke binoculars. All binoculars are also supplied with an eyepiece cover.

Tripod Cover - This covers a tripod thread that can be used for binocular tripod mounts.

Objective Lens - Larger objective lenses give better light transmission and allow for a brighter picture.  A larger objective lens will allow the binoculars to be used in lower light conditions.

Textured Grip - Designed to give extra grip while being ergonomic to the touch.

Twist-up Eyepiece - Typically with 3 different height settings, the twist-up eyepieces can be set to ensure the best eye relief for your use.  Glasses wearers often leave the twist-up mechanisms in the downward position, while non-classes users wind the twist-up mechanism into the upright position.

Terminology & Phrases

Eye Relief - The correct distance for the pupil to be located from the ocular lens.  When at this distance the best viewing experience will be obtained.

Exit Pupil - The diameter of the viewing image when the eye is positioned at the correct eye relief.  This is calculated by dividing the objective lens diameter by the binocular magnification. e.g. for a 10x42 binocular we divide the objective lens diameter of 42 by the magnification power of 10 to get 4.2mm.

Field Of View (F.O.V.) - The width of the binocular's view.  This can be measured in terms of angle (degrees), or by a set distance. e.g. the F.O.V. of the Sapphire ED 8x42 is 142m wide when looking at an image 1000m away.  This is also equivalent to 426ft wide when looking at an image 1000yds away.

Close Focus - The closest possible distance that the binoculars can be focused at.

Interpupillary Distance - The distance between the two ocular lenses.  This is measured from the middle of one lens to the other.

Fully Multi-Coated (FMC) - Means that all lenses and glass surfaces have a coating layer. Multi-coated means that at least one of the major optical elements in the binocular has a coating.

Extra-Low Dispersion (ED) - ED glass is a different type of manufacturing process designed to remove chromatic aberration (colour fringing).

Phase Corrected (PC) - like ED glass, PC glass works to stop chromatic aberration, but is lower cost and not as effective as ED.