Sensors are linear devices. If you double the amount of light, the sensor output will double, as long as the
pixels are not full
(*). Once a pixel reaches full capacity, it will give a constant or "clipped" output. Human vision is non-linear, as explained in the
dynamic range topic. A doubling of the light in low light conditions has a much larger effect than in bright conditions. Our vision amplifies the shadows and compresses the highlights.
