Itachi Uchiha being from the Uchiha clan knows a lot about the sharingan. So, he started confidently.....
The Sharingan is the curse of the Uchiha. It is one of the great three Dojutsu Kekkei Genkai, which appears to only some people of the Uchiha clan. The sharingan is achieved with suffering and pain in life threatening situations. The sharingan has may godly abilities which make it desired for lots of shinobis. Sharingans basic ability is to see the chakra flow when activated. The eye's power gives a colour to chakra allowing the wielder to differentiate them. Because of this,the user also has the ablility to see if someone is under a genjutsu because then the chakra flow of the observed person would be irregular. The second ability grants the user an incradible clearity of perception thus giving them the power to recoginze genjutsu and diffrent chakraforms or te ability to predict your opponent's movement,and thus counter them. This ability also allows the user to pick up subtle details enabeling them to read lip movements and/or mimic something like pencilmovements. As your sharingan gains more tomoes this ability improves untill it gives the wielder such clarity that he/she can predict enemies attacks, allowing them to see the opponent's next move from the slightest muscle tension in their body. But meanwhile seeing the attack doesn't assure the user that he will definetly avoid it. Sharingans last ability is to copy almost any technique that it sees (as long as its not a kekkei genkai or summons that requires a contract)
The final ability is that the sharingan can put someone under hypnosis simply if the person looks the wielder in the eye(s). More advanced and experienced sharingan wielders can even hypnotise Summonings like Manda or even a tailed beast and controll them.
The sharingan has many stages. The staes are as follows.
1 tomoe- This type of Sharingan has 1 tomoe surrounding the users pupil and is gained at the moment of awakening the Sharingan. It allows the user to perceive motions and see chakra. The user's pupil turns bloody red, and gains an extra pupil, or tomoe within each eye that will surround the original, centered pupil. When active the user now has the ability to track speeds that would only be seen by a higher ranked, more experienced ninja. They also gain the ability to see through visual D rank genjutsu (visual illusions) and can follow the movement of most taijutsu moves done by normal Shinobi, even those faster than the user and the movement of most Ninjutsu, allowing one to be able to react best to the situation.
2 tomoe- It allows the user to perceive motions as well as be able to copy the motions perceived as long as he is able to perform them physically. When activated the user's eyes turn blood red, and gain two extra pupils, the tomoe which surrounds the original pupil. At this level the user gains a better understanding of the sharingan. The user can now anticipate and analyze faster movement, as well as mimic minor movements made by an opponent. The user can now track higher speeds (almost twice as fast) and, by reading the handseals, can predict to some extent the use of Ninjutsu techniques (but will always obey and abide by the time frame rule as he can never start performing a counter/move before the opponent has started his, meaning that there will always be a logical sequence of moves that will obey the time frame). The user is now able to pierce through visual C rank genjutsu and below.
3 tomoe- This is type of Sharingan has 3 tomoe. It allows the user to perceive motions, copy the motions perceived, and predict motions. An example of this is during the fight between Sasuke and Naruto at the Valley of the End. Sasuke could perceive Naruto's motions, copy them, and than predict what Naruto was going to do next. Essentially, to Sasuke through use of his Sharingan, it looked like Naruto was going in slow motion. When active the user now has the ability to keep up with extremely high speeds and mimic basic taijutsu exactly. With this the user can now copy handseals done by an opponent (using the adequate Copy Technique), and use jutsus as they do as long as he's able to perform them (having the adequate chakra nature, adequate knowledge of the field of expertise being copied, etc). The user must however be able to mimic the techniques, for if they are not physically able to preform the copied techniques they cannot do them. The user can now pierce through visual B rank genjutsu and below. Unlike the previous two sharingan stages this level has the ability to hypnotize a target. If however the target is too strong the hypnotizing with be ineffective. This can only be done on targets one rank below the user and through eye contact. The user will need to spend a move to activate it and will be able to keep it active until the end of the match as long as he has chakra and stamina for it.
Mangekyou sharingan- The Mangekyo Sharingan, literally meaning "Kaleidoscope Copy Wheel Eye", is the second highest known form of Sharingan (the first being Eternal Mangekyo Sharingan), feared by many as one of the strongest KG of the Ninja World. The appearance of the pupil drastically changes, differening from the normal tomoe seals, with the MS's shape differing from user to user. When active the user can track speeds even further beyond that of the third stage sharingan. The timing of the users counters, the chaining speed of multiple techniques and the ability to see through the enemy's moves greatly increases. Not only that but the user gains the ability to see through visual genjutsu A rank and below. The link to Genjutsu is further increased and, if the user has gained full mastery over Genjutsu, he gains the ability to cast any and every genjutsu without the need for Handseals through simple eye contact. Also, the Mangekyo Sharingan gives the user access to powerful and forbidden techniques, unique to each user. Extended use of the Mangekyo Sharingan after some time, deteriorates the user's eyesight to the point of blindness. After some times they become blind.
Eternal mangekyou sharingan- The Eternal Mangekyo Sharingan literally meaning "Eternal Kaleidoscope Copy Wheel Eye", is the highest known form of Sharingan, said to be feared as the strongest doujutsu. The appearance of the pupil drastically changes, differing from the users original MS pupil and takes on the shape that combines both his and his brothers MS pupils. When active the user can track speeds even further beyond that of the MS. The timing of the users counters, the chaining speed of multiple techniques and the ability to see through the enemy's moves greatly increase even beyond the levels of MS. Not only that but the user gains the ability to see through visual genjutsu A rank and below. The link to Genjutsu is further increased and, if the user has gained full mastery over Genjutsu, he gains the ability to cast any and every genjutsu without the need for Handseals as long as he has a clear line of sight to the target. Also, the Eternal Mangekyo Sharingan gives the user access to the same powerful and forbidden techniques availabe to the user through his MS and even some additional ones. Uchiha Madara however, has the ability to use not only his unique MS abilities but also the generic ones such as Amaterasu and Tsukiyomi. The will, however, not suffer any damage or decrease in his EMS activation time limit through the use of these techniques.
That............I hope is enough. Now, if you can activate my sharingan then I will be powerful enough to protect Konoha.
The lines about the stages I did copy from NB jutsu descriptions but believe me I have read and understood them perfectly.
