The time for visual persistence is typically taken as 1/30th of a second; what is the minimal time a light should be on to recognize its brief presence ?

Example, a high speed mechanical shutter wheel in front of a light source.  (Or a pulse on LED)  The light passes a slot to the eye for one millisecond.  Probable visible.  What if one microsecond ?  Would that time be long enough to be detected by the eye ?   

Is there a name for that 'time sensitivity' ?

It’s going to depend on how bright the light is, since this is related to how many photons you need to collect to see it.

Thank you.

Found some reading on the photons subject.  Believe there is no such thing as half a photon, right ?

----> https://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html#:~:text=Since only about 10% of,actually required at the receptors.