Dannj wrote:
I found a box of slides in my attic that are about 50 years old and faded. Can they be restored?
Well, you cannot put back what was not there to start with, OR what has faded, but you may be able to restore much of the color BALANCE by manipulating the controls in a scanner driver or post-production software. SOME underexposure errors may also be adjusted.
Last year, I took slides, negatives, and prints from dozens of my college classmates' collections, digitized them, and made a 45-minute video for our 45th class reunion dinner. It ran silently in the background throughout a cocktail party, dinner, speeches, and after-dinner chats. Producing that show gave me a lot of valuable experience with what can and cannot be done to make old photos look good.
Some Epson scanners come with an old version of Digital ICE, software once developed by Applied Science Fiction and Kodak. It removes dust and scratches and can do some rebalancing of color. It will not work on the latest Macs, but can be run on Windows and older Intel Macs that are 32-bit compatible (running MacOS 10.13).
If you have a newer Mac, Epson provides a link on their website to a free download of a SilverFast scanner driver software with ISRD, a technology that uses the same features of the scanner that Digital ICE used.
Instead of scanning, I prefer to copy my slides and negatives with a mirrorless camera, a macro lens, a color-accurate light source, and the Essential Film Holder. I'm able to do a lot with copies of film by using Adobe Lightroom CLASSIC and Photoshop to convert my raw files, adjust color, spot dust, etc. The attached white paper (PDF) explains what I do.
Unfortunately, Kodachromes are the only slides that truly last. Even Kodachrome slides from the 1930s can be in pristine condition if they were stored properly. Most other films have faded. My Ektachromes went blue, Fujichromes went pink, Agfachromes went red, and my uncle's Anscochromes faded slightly towards brown. All my 3M/Ferrania slides just went nearly clear, along with all my Mom's purchased slides of Europe and Russia made on 1970s color print film (movie print film stock).
When a slide has faded so severely that the color is just "plug ugly", converting it to Black-and-White is a possible solution.