A light is on or it’s off. But, for a moment, it is both. When slowed down to an infinitesimally slow speed, it transitions from being on to being off. This happens quick enough as to seem simultaneous, but it could not be.
Not anymore than leaving the house. You are not inside and then suddenly outside. There is a transitional period. If you stand in the doorway, you are both outside and inside. If it were possible for a person to stand in a doorway infinitely, why not a light?
Frozen Light (TM) sprang from this query. The light could be on for one person and off for another. Of course, the user still has to flip their personal switch manually, but that has become as familiar as making a phone call.
The phenomenon of light became malleable to an individual’s will. From studying the instant of transfer between illumination and darkness, we managed to change the physical reality of our world.
This is also how we learned to freeze the moment of death.