Jim wrote: “I have an 1884 photo of my gg grandfather and grandmother with 2 of their children. On the back of the photo I can see some written impressions of names possibly. The pencil marks have long since worn away. Can you suggest a process that I might highlight the pencil impressions so that I might read them? I want to be careful, because it is the only know picture of them.”
Without seeing the photo I can’t say for sure but there are at least a couple of techniques that could work. I’d try scanning the image then converting it to black and white. By playing with the contrast/brightness and then using zoom to enlarge the impression you should be able to decipher some details. I’d also print out an enlargement of that area and then tracing it with a pencil.