And so, as you would also have seen if you had watched the videos on the basics 😉, the device has 3 ways to let light in, and only 3:

1. The first is the exposure time, which means you can leave the shutter open for a longer or shorter time - also known as the shutter speed.
2. The second is the aperture of the diaphragm, that is to say how much the diaphragm of your cine lens will be more or less open, and that depends on the cine lens. Because the goals are limited compared to that, they can't fully open all the time.
3. And the ISO sensitivity, which is basically the mathematical multiplication of the light by the sensor, to put it simply.