Board Thread:Naruto Discussions/@comment-3232093-20140617193601/@comment-25076530-20140618042339

This is how I think the Sharingan/Rinnegan work:

- Sharingan and Rinnegan are just labels for the various levels of power of the Shinju Eye, passed down through Kaguya's bloodline.

- Eye strength tends to diminish over generations.

- Sharingan = Shinju Eye minus the "Senju" chakra

- Purple Rinnegan = Weak form of Rinnegan (no tomoe)

- More tomoe = more power, Sasuke's Rinnegan is stronger than a purple Rinnegan but weaker than Kaguya's third eye (full power Shinju Eye)

- Human Madara awakened a weaker Rinnegan than Sasuke because Madara was infused with a small amount of Senju chakra, while Sasuke was infused with a large amount of Hagoromo's chakra.