When do photographs become photo illustrations?

When do photographs become photo illustrations? – Conscientious:

It has become fairly obvious that lately that our understanding of what photography is and does has not quite caught up with, well, what it is and does. A wonderful case in point is the attempt to differentiate between “photographs” and “photo illustrations”. What is the difference? When does a photograph become a “photo illustration”? If you think the answer is so simple keep reading. I don’t think it is.