How far and how clear could the "Eye of Sauron" see? Could it see through the whole of Middle-earth or is it limited to only Mordor? Could it distinguish the human face, the small artifacts like rings, or not?
Saruman says the "Eye of Sauron"
"sees all — his gaze pierces cloud, shadow, earth and flesh. You know of what I speak, Gandalf — a great Eye… lidless… wreathed in flame"
when he is intimidating Gandalf. This implies that Sauron could see everything, just like Superman. If this is true, how could the One Ring escape his gaze? Sauron just needed to scan the land of the Shire. I am afraid that the meeting in Rivendell is also under Sauron's sight. When Frodo brings up the One Ring and Gimli wields his axe, Sauron will see. And once he saw the Ring, he can see it always.
Does this mean that Saruman is exaggerating? What is the true limit of the "Eye of Sauron"?