The Uchiha family’s bloodline limit, which consists of red eyes, Sharingan allows the user to perceive motion clearer than normal eyes, sees through Ninjutsu and Genjutsu, copies motion and even ninja techniques, and can subliminally input ideas into its victim - Mangekyou can even induce extremely powerful hypnosis. The Sharingan needs to be activated by the user when they are faced with a difficult circumstance or placed under emotional stress.
1 tomoe: the Sharingan's power, because of its ties to the Curse of Hatred, is both a blessing and a curse. The moment that an Uchiha comes to know a powerful emotion towards someone, such as love and friendship, a stressful or emotional condition brought out from losing that precious person causes the brain to release a special form of chakra that affects the optic nerves while transforming the eyes into Sharingan. 1 Tomoe sharingan allows you to see the opponents faster movements in slow motion and giving you an advantage because normal eyes can see really fast movements.
2 tomoe: To be honest i really don't know if there is that much of a difference between a 1 tomoe sharingan and 2 tomoe shanringan but i believe that a 2 tomoe sharingan gives you the ability of better tracking the opponents movements, allowing you to track even more faster movements. I think it also allows you to copy moves but i might be wrong.
3 tomoe: i believe allows you to predict movements and also gives you the ability to track the opponents movements much faster than the 2 tomoe. I believe it gives you the ability to see the chakra color.
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A: Ability to see color.
1: Motion perception.
2: Copies all motion perceived.
3: Prediction motion- inferring through rational physics the action about to take place.
B: Ties pupils together for the ability to understand what one sees without getting confused. Without it, you would have three different eyes looking in three different directions and no idea what to focus on or what’s going on.
Well Uchihas are pros when it comes to genjutsu, a great example is Itachi who has a deadly genjutsu technique. I know that uchihas by making eye contact can put an opponent under a genjutsu. Also uchihas can be put under a genjutsu but they can notice it by looking at their chakra color i believe.
I know i missed stuff, so anything else add it please. xD