Even in todays world of still photog�aphy, there are always mechanisms in place to limit the amount of light that is reaching the sensor which
helps in making photog�aphs. One of the mechanism is the aper��re cont�ol and the other is the shutter.
The human eye equivalent of aper��re would be the iris which cont�ols the amount of light that is admitted into the human eye but there is no
equivalent to the shutter. Why? because our eyes perceive a continuous st�eam whereas for still photog�aphy it is just one frame that is capt�red.
The shutter mechanism in earlier film cameras used to be a moving physical ‘shutter’ that used to, for a brief moment, let light into the camera
and close back such that it is sufficient to for� an image on the film. Today the mechanism could be as simple as just t�r�ing off the sensor aſter
the necessar� light has been capt�red, as it happens in most mobile phone cameras.
Simply put, duration for which the film is ex�osed is what is technically deter�ined by the shutter speed and in todays world it is sufficient to
know that, all things remaining same, a higher shutter speeds ex�oses the sensor less to light than a slower one.