Magnification and objective lens aperture
Like a telescope, the first indicator you see when choosing a scope is a series of numbers like 4x20 and 4-16x50. The front number represents the magnification, and the back number represents the aperture of the objective lens (in mm). 4x20 means 4 times magnification, objective lens diameter 20mm; 4-16x50 means magnification can be adjusted from 4 times to 16 times, objective lens diameter 50mm. The larger the objective lens, the greater the light input, and it is easier to see the target under high magnification and poor light conditions, which is accompanied by an increase in volume, weight and price. Is the greater the magnification, the better? The answer is no. The larger the magnification, the smaller the field of view. It will be difficult to lock the target in a hunting environment.
Exit pupil distance (eye relief)
The exit pupil distance is the distance between the eye and the eyepiece when a clear and complete field of view can be seen. The recoil of the centre fire rifle is obvious. In order to prevent the sight from hitting the eyes when shooting, the exit pupil of the centre fire rifle scope is usually relatively large. The exit pupil distance is usually not an indicator that everyone pays special attention to when buying a mirror. Any rifle designed for rifles without specifically marked rim fire or scout (large exit pupil distance) will ensure a safe exit pupil distance.
The scope of the scout type rifle has a large exit pupil distance, which is not suitable for normal rifles.
The reticle (teticle) is the grid and lines seen from the scope. The most familiar crosshair is a kind of reticle. There are many types of reticle, common ones are crossfire, duplex, mildot, BDC.
Mildot further divides the crosshairs, and there is a Mil between every two dots. Mildot provides more aiming points, and can be used for shooting at different distances, shooting at moving targets and distance calculations.
The picture on the right is a reticle that can emit light, which is very suitable for use in low light.
