A common problem with old black-and-white or sepia-toned photos is that they fade over time. You can use a Levels or Curves adjustment, but both commands often introduce color artifacts into the image. A few extra steps are needed to get the best results.
1. With the Eyedropper tool, sample the color tint if you want to retain it in the finished piece.
2. Leave the photo in RGB mode but strip away the color. Choose Image > Adjust > Desaturate or press Shift+Command+U (Shift+Ctrl+U).
3. Perform a Levels adjustment and restore the white-and-black points. Drag the black Input Levels slider and the white Input Levels slider toward the center.
4. Add a Solid Color fill layer by choosing Layer > New Fill Layer > Solid Color. Click OK. The Foreground color you previously sampled will load automatically.
5. Set the Color Fill layer to use the Color blending mode. Adjust the Opacity slider as desired.