Courtesy of Mr. Grassi, Mr. Shepherd, Tiger McKee and The Tactical Wire
"You're in a tight spot. You'll probably have to shoot to solve the problem. Your visual focus is wide, taking in the info needed to make decisions. Once you decide to shoot, your focus shifts to the exact point on the target you want the bullet to go. The pistol comes up, the sights intersecting the line of vision between your eyes and target. At this point your focus shifts to the front sight. On a close, large target we use a "flash sight picture." As soon as you see the front sight you're pressing off shots. As the distance increases, or the target decreases in size, more accuracy is required. You focus more intently on the sights, making sure the front and the rear sight are in alignment. This is a "dedicated sight picture."