What are the most common ways realistic textures are made in game studios today?

dosit

Are they hand painted, from photography, sourced from the Internet , pbr etc 

PixelMasher

more and more games are using substance or quixel, but i know a bunch of artists who still use photosource textures, photogrametry, whatever works. there is no correct way of doing it, just make something that looks good. but generally starting from a photo base or using it to create substance masks will help.

musashidan

Highres scanned and polarised source images would probably be the most realistic option available.