An aircraft's apparent size and a tracer's light intensity change at different rates with distance. The comparison uses an inverse-distance change in apparent size and the inverse-square decline in light intensity. Tracers therefore have limitations as visual aids to aiming. Their visible approach can still have a useful psychological effect on the target's pilot.
Notable Point · 3:41:51-3:42:24
Tracer visibility changes with distance
Different rates of change in apparent target size and tracer brightness complicate aiming, while visible incoming fire can still unsettle a pilot.