Photo reference

Photo-referencing in visual art is the practice of creating art based on a photograph. Art produced through this technique is said to be photo-referenced.

Almost all artists will photo-reference at some point; even if not in their daily work, artists may photo-reference as part of their training, to improve their artistic eye.

Photo-referencing, rather than working with live models, is useful for cases in which an artist seeks to realistically produce a work of art based on some subject that is not readily available, such as specific person who is not there or a structure in another country.

Artists may use a lightbox as an aid in photo-referencing.

In the comic book industry, photo-referencing is criticized by some as a technique used to disguise the weakness of the artist's technical capability. However, others feel that photo-referencing is a legitimate technique and that there is nothing wrong with it. Artists that have been charged with excessive photo-referencing by their critics include Greg Land and Alex Ross, though others defend the quality of their work. Award-winning comic creator Alison Bechdel also uses extensive photo reference, frequently photographing herself in the poses of the characters she draws in order to convey body language accurately.

...
Wikipedia