I often hear people say that shining a light in an attackers eyes is either effective, or conversely I hear it is not. These pictures are from a flashlight used by a student in a force on force class. The light itself was hit by a sim round, in that same class I was shot in the wrist a few inches below my flashlight bezel. In a completely separate class I was told by several students that shining a light in their eyes made it impossible to hit me.
I think there are several factors to consider here.
In my experience the level of brightness does effect how someone reacts. The brighter the light the more effective the flashlight is to make the attacker turn away from you or wildly shoot in your direction. Barring bad luck, brighter seems to be better.
The farther from my attacker I was the less effective the light was. The light seemed to dissipate in space no matter how focused the beam was.
The beams with the most focused lights delivered more brightness on the intended target. Beams with a wide throw were less effective.
Walking around with the light on searching the room is a very bad thing. It screams out where you are. Lighting a suspected target momentarily, moving, assessing what you saw, then relighting the target and engaging seemed to work very well.
Bouncing my light beam off the floor or ceiling to illuminate the room seemed to be an effective way of identifying what’s in the room. Shining the light directly in the face of the attacker worked much better than anywhere else on their body.
What I picked up after several low light tactics classes was that flashlight choice and tactics matter a lot more than people think.
The flashlight should be as bright as you can possibly carry. The beams throw should be as concentrated and pinpointed as possible. The button on the back should be momentary only, no constant on. The light should have only one mode, extremely bright. The button should be shrouded if possible to stop negligent discharges.
Be aggressive with your movement, and sparing with your use of light. Use other objects like walls, floors, ceilings, and even furniture to your advantage. When engaging your attacker shine the hottest part of the light beam directly in their eyes.