Good Evening, all...

I had a photo that was taken in 1958, which over time, had badly faded. We happened to find the original negative and had it printed with excellent results. My question -- has there ever been a study to compare an original image with a faded one to determine if a filter could be written to restore back to original colors with a slider type filter? Secondly, does anyone know if colors fade equally?

I don't know if anyone has created a filter that would restore colors to their original look. It would be quite a trick for a filter to be able to tell if a color is faded because of light or if it looks exactly as it was.

Colors don't fade equally: since colors have different wave lengths, they are affected by UV light differently.

This article (http://www.nedcc.org/resources/leaflets/2The_Environment/04ProtectionFromLight.php), while somewhat technical, explains well what happens with the color fading process.

Good Evening, all...

I had a photo that was taken in 1958, which over time, had badly faded. We happened to find the original negative and had it printed with excellent results. My question -- has there ever been a study to compare an original image with a faded one to determine if a filter could be written to restore back to original colors with a slider type filter? Secondly, does anyone know if colors fade equally?

There a many reasons why colors fade that have to do with chemical reactions in the paper (of film) and the dies or emulsions. Colors fade to different degrees differently. There are a whole pile of filters that are designed to help restore faded colors. Some come pretty close. You can try Kodak's Digital ROC or Picto Color's 1Click iCorrect and there are dozens more out there.
Regards, Murray