I admit I don't understand all the technicalities explained in this YouTube, but whoa! is Time-Travel Rephotography ever fascinating (and more than a little scary). If it does nothing else for historical fiction writers, it should educate us in the ways older cameras distort people's faces so that, given an old photograph, we can try to imagine people from the past more sensitively. But like all doctored photograph, it is also a reminder of the ways we can be manipulated by computer programmers—although for speculative fiction writers, just think of the doors it opens!
Via Gurney Journey's Bringing Old Photos to Life, which discusses it and another app. from a color-specialist and animator's point of view.