I happened to think of another example... Say that you are viewing a cable that is traveling in front of a shadow in such a manner that it has a strong contrast to the shadow, thereby giving it a hard edge. The cable, then, turns and travels into the shadow in such a manner that it obtains the same value and hue of the shadow and becomes invisible, thereby giving it a lost edge. Then, it turns again and travels out of the shadow. As it comes into the light its edge becomes apparent and is seen as a soft edge. But, then, as it nears and enters into the strong light, it becomes a hard edge.
