Deses wrote:What's the current consensus regarding the time of this change? (Y to I and so on).
They happened at different times. [face=spionic]ei[/face] started to shift about 4th century BC, [face=spionic]h[/face] about the 2nd AD. The diphthong [face=spionic]oi[/face] united with upsilon in the 2nd or 3rd century, then both went to iota only toward the end of the millenium. (All this from Palmer).
How did those rare medieval westerners who actually knew Greek pronounce Greek words before Reuchlin and Erasmus had it all "straightened out"?
They learned from Greeks, so I believe the pronounced everything like their tutors, i.e. as Modern Greek, iotas everywhere.