Thank you very much for answering my previous question. That taught me a number of new techniques, and did a very good job of removing the orange stain and preserving the sepia tone. Now I have another question: How, with GIMP, do I most easily make the area shown in the red outline darker and more contrasty, without changing its colour? I guess that there was either light leaking into the camera, or some error was made whist developing and printing the original photo to create this lighter area. Thank you - Rowan
Ahh… this is one where my first thought does have an equivalent in Gimp.
This is two seconds in Photoshop, Gimp should be similar [more care == better results, of course.]
Settings were soft brush, Midtones, 100%