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The eye relief of an optical instrument (such as a telescope, a microscope, or binoculars) is the distance from the last surface of an eyepiece within which the user's eye can obtain the full viewing angle. If a viewer's eye is outside this distance, a reduced field of view will be obtained. The calculation of eye relief is complex, though ...
The longer the focal length of the eyepiece, the greater the eye relief. Typical telescopic sights may have eye relief ranging from 25 mm (0.98 in) to over 100 mm (3.9 in), but telescopic sights intended for scout rifles or handguns need much longer eye relief to present a non-vignetted image.
An eyepiece, or ocular lens, is a type of lens that is attached to a variety of optical devices such as telescopes and microscopes. It is named because it is usually the lens that is closest to the eye when someone looks through an optical device to observe an object or sample. The objective lens or mirror collects light from an object or ...
The eye relief was only 38 mm (1.5 in), so the sight was equipped with a rubber eyepiece shield to prevent the scope from hitting the face during recoil. The reticle was a thin crosshair, as was common for this time period. [4] These sights were fitted to the Hotchkiss M1909 Benét–Mercié machine gun. [5]
A C79 Optical Sight. The C79 optical sight (SpecterOS3.4x) is a telescopic sight manufactured by Elcan. A variant, the M145 Machine Gun Optic is in use by the US military. It is 3.4×28, meaning 3.4x magnification, and a 28mm diameter objective lens. A tritium illuminated reticle provides for normal and low-light conditions sighting. [ 1 ]
Generally, an eye relief over 16 mm should be adequate for any eyeglass wearer. However, if glasses frames are thicker and so significantly protrude from the face, an eye relief over 17 mm should be considered. Eyeglasses wearers should also look for binoculars with twist-up eye cups that ideally have multiple settings, so they can be partially ...
Zeiss inner rail, [1] generally simply referred to as Zeiss rail, is a ringless scope sight mounting system introduced by Zeiss in 1990 as an alternative to traditional ring mounts. [2] A patent was granted in 1992, and the patent expired in 2008. [3] [1] The mounting system is now also offered on sights sold by other major manufacturers, such ...
Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight and is measured by the angle or half-angle of inclination between those two lines. [1][2] Due to foreshortening, nearby objects show a larger parallax than farther objects, so parallax can be used to determine distances.