Simply put, I'm wondering if the following is possible to do:
1) Have images A, B and C somewhere on the computer
2) Image A contains a black background
3) Images B and C contain photos of two persons with backgrounds removed
4) You open images B and C, set image A as the background to both, while somehow linking it to the actual file of image A
5) You later open image A and slightly brighten it up to, say, dark gray
6) You then open images B and C, and find out that the backgrounds in those images have changed to dark gray as well.
And that's what you were after.
Is this possible? I spent a short while looking for "external reference" or a similar option, but couldn't find anything. There was "Place"-command in the file menu, which added the selected image file as a layer (and apparently as a smart object at that), but it was in no way linked to the actual file I had chosen in the Place-dialog - that is, if I opened and edited the image I chose, the changes wouldn't automatically carry over to the other file, when opened.
So if you've understood what I'm trying to do here, do you know if something like this is even possible in Photoshop CS2?