The light is off in the room. The brightness of your phone would ruin the performance. - you are on a wedding of your friends and you are making a video or taking photoes of the event. The brightness of your phone would ruin the event. - you are invited to the concert of your friend. You are sitting in the first row and would like to take some photoes or make video. The brightness of your phone would bother the others whom would like to enjoy the performance.