Mucha — poster for DeForest Phonofilm — 1927
Mucha himself and his daughter, Jaroslava
— reference for poster — 1926
Larry MacDougall put it well in his comment, when he said, "Of course the photographs are lovely, but you can really see how (Mucha) transfuses them with magic. And of course like all magic, only the magician knows how it is done."
And to put it further into perspective, here is a quote for an article about the subject:
Comparing Mucha's design with the photos from which he worked gives us useful insight into the artistic process. It is clear that no photograph was ever slavishly copied; it represented only a point of departure from which inspiration takes over. With his meticulous attention to detail, Mucha certainly used the pictures to check things such as the precise position of fingers on a hand holding something—often a stumbling block for even otherwise competent artists—as well as for a correct perspective and spatial relations between people and objects. Beyond that, the heart of every design is an expression of the artist's soul.