St. John Vianney could have been the oldest, but
During his lifetime, the Curé d'Ars has always refused to pose for a portrait or to be photographed. In the absence of such a testimony of the physical reality of the saint, one could legitimately wonder about the fidelity of the many images representing him. This uncertainty led, in [September] 1959, the Sacerdotal Session, on the occasion of the centenary of his death, to ask the divisional commissioner Chabot to make a "robot photo" of the Curé of Ars from various documents presenting a scientific certainty, essentially the mortuary photographs. The photo reproduced here is the result of this command.
Saint Jean-Marie Vianney
So I don't know if this counts but its more photo realistic, and probably from right around the same time as St. Bernadette's photo