What gun will it be used for? The first thing to be clear is what you intend to install the scope on. Different firearms have different interfaces for installing accessories, the ammunition used is different, the recoil produced is different, and the sighting equipment that can be installed on it is different. For example, the scope used on the rifle and the scope on the pistol (yes, the scope can also be installed on the pistol) can not be the same only in the indicator of the eye distance, because the pistol is not the same when shooting. Like a rifle, you can stick your face to the butt but keep a certain distance from the human eye, so you must have a long eye distance. In the same way, the scope used on a scout rifle (also called a scout rifle) is usually installed in the front part, so it must have a longer eye distance. Long eye relief (LER) scopes usually do not have high magnification.
The eye distance of the pistol scope (top left) and the scout rifle scope (top right) is much larger than that of the ordinary rifle scope (bottom). The so-called eye relief (eye relief) means that it can be used without vignetting. The best distance (between the human eye and the eyepiece) that provides the human eye with the largest field of view is the distance most suitable for the human eye to observe comfortably. If the distance is greater than or smaller than this optimal distance, vignetting will be produced and the observation quality will be negatively affected. The reason for vignetting is that the human pupils only allow limited light to enter the eye. If the light from the target is partially blocked by the iris, not only will the image partially covered by the black shadow be projected on the retina, it may also be distorted Interfere with the image light that has entered the pupil. At the eye distance, the possibility of vignetting is the least. In addition to eye-fitting distance, exit pupil is also a relatively important optical parameter that is often overlooked and often confused with eye-fitting distance. The exit pupil diameter is the diameter and width of the aperture (exit pupil) projected by the eyepiece at the eye distance, which is a length value perpendicular to the eye distance. In the case of sufficient light (such as light and Hitachi’s broad daylight), the diameter of the human pupil is usually about 2 mm. As long as the diameter of the aperture produced by the eyepiece at the eye distance is greater than 2 mm, it can basically guarantee that even the human eye Vibration will not produce vignetting; but if the brightness of the light drops (in low light conditions), the human pupil will dilate. If the diameter of the eyepiece aperture is smaller than the dilated pupil diameter, vignetting will also occur at the proper eye distance . Therefore, when buying a scope, try to consider choosing a slightly larger exit pupil diameter.
