I already knew about the concept of shutter speed and long-exposure photography, but this detail about cameras is making me curious about how the image sensor collects light as a function of time. Is the image sensor collecting light continuously for as long as the shutter is open, or does it have to implement some kind of polling/sampling mechanism to collect light in discreet intervals of time? And for either scenario, how is that actually implemented? I saw in an earlier slide that a sensor "accumulates irradiance during exposure", but I'm not sure what that actually means and how it's done in practice.
@krentschler When light falls on a pixel on a CMOS sensor, it causes charge to accumulate in a capacitor. This total charge is what is interpreted as the brightness of the pixel. So, for most SLRs, the sensor collects light continuously as long as the shutter is open.