Contributed by B@rt.
"What makes an image photoreal? Actually there are literally thousands of things that make an image photoreal but they all fall into 10 categories that I call 'The Principles of Photoreal 3D'. These principles are the guidelines to ensuring an image is photoreal."
A very cool tutorial by Bill Fleming.
https://mastering3dgraphics.com/public/freestuff/tutorials/general/reailty_is_chaos/index.html