Artists have been using photographic reference material to paint from, since Victorian times. Even the PreRaphaelite Brotherhood used them, although theirs were of course, not in colour. Years ago, I read a book on the techniques used by the fantasy artist Boris Vallejo, and in it he demonstrated how he used studio photography as a basis for creating his oil paintings. This was long before computers became everyday items.
These days it is easy to use very sophisticated art software in ways that take the “photo to painting process” to another level entirely.
Vallejo generally employed models to be photographed in empty studio settings. He would later add his backgrounds from other sources. Often he would create mythical beasts from his imagination, that were based on his human models.
I work in a similar way, but with modern computer art programs and a drawing tablet (currently a “Ugee”) I may easily combine the separate elements such as models, backgrounds, props and costumes into a single working image. I can even add imagined details over the top of my source photo, “painting” with my “pen” and tablet.
This process is a boon to the modern day artist, and speeds up the thought processes towards creating finished paintings. It allows an artist to virtually “see” what any painting might end up looking like, long before he commits to canvas and real paint.