Board Thread:Theories and Speculation/@comment-34656247-20190723175508/@comment-26636534-20190724124237

This is an interesting topic, however it's not as simple as one might think. The Sharingan allows for predictive and perceptive insight. Predictive, being analysis of micro-movements simulating where/what/how the opponent will react or move to, for a counter offensive. Perceptive being limited analysis of chakra/objects and "zooming" functions.

So, using this as a base to answer your questions:

'''Mention fast characters as an example if you will.. characters can also be from other mainstream anime.'''

Ay's speed is an obvious example of Sharingan users not able to track but still able to predict. (Although wasn't that the MS though?) Therein lies the distinction, just because the sharingan can't track you, doesn't mean it's predictive abilities are void.

On the other hand, just because the sharingan can track someone, like Bee, does not mean that it allows for 100% accurate prediction. As Bee was able to, use several moves that Sasuke could not predict.

'''Is lightspeed possible? ''' In terms of observation, yeah, just like with anyone else. There is a misconception, that predicting a fast attack with the sharingan is a pure mental reaction, when it is actually preemptive, planned and timed correctly.(cough* Kirin cough*).

There is the added variable of the speed of the user, both reaction and movement. Plus, having jutsu powerful/fast/usable enough and compliment the sharingan itself. Combining proficiency of prediction, perception, reaction speed and physical speed is what makes elite sharingan user's rare. That's why only a few among the Uchiha became well known.