SIGHT ALIGNMENT
This is the process of making sure all components of a sighting system are mechanically aligned with each other, and with the eye. Iron sights have three points of alignment: the front sight post, the rear sight aperture, and the eye. Red dots and magnified optics have two: the reticule and the eye. A proper and consistent cheek weld that allows the eye to look directly through the center of the aiming device is necessary. If the alignment between the firer’s eye and the aiming device changes between shots, it will increase the grouping size of multiple shots.
SIGHT PICTURE
Once the sights are aligned and placed on the target, a sight picture is achieved. During the course of follow up shots, the sight picture must be continually moved back to its original position on the target or adjusted as necessary.
The human eye can only focus on one plane at a time. It is important that the shooter focus on their front sight post or reticule, rather than the target.