For you photographers out there, the English language has a peculiarity concerning how we turn on or off the light. When a light goes off, it usually means there is darkness. However, when a flash goes off, you will get light instead.
I guess this has to go along with the rest of the confusion in photography. Take aperture, for example. To increase the aperture you have to set to the smaller f-number, and vice-versa for decreasing the aperture.
Did I say confusion? Oh yes, there's the "circle of confusion" associated with how the image is focused. Google and read about it at the risk of confusing yourself.