There are small details that can tell u the difference between photography and a drawing. If u look at this photo at certain distance u can't tell if this one is photography. There are artists that perfected the pencil drawing technique so much, that the only thing that u can be sure that it is not a photography is to take your finger and smudge a small part of the drawing. But there are not so many drawings that are microscopically perfected in that way, so u can search for things that are not normal, or things the artist could not do as planed. Those are the things that usually not in a real photography, things that u know how they look when u capture them.
