Photographic Masking Methods.
A mask is a separate image that can be combined, in register, with the original image in order to create produce a modified image. The technique has been extensively used in restoring still photographs, and was used for the correction of unwanted dye absorptions in preparing prints from colour photographs in the graphic arts industries. The old Dye Transfer, Carbro and Vivex paper colour printing systems all used masking wherever the original was a colour transparency.
The technique will provide excellent correction for faded dyes but is extremely difficult to apply to small images repeatedly. The process entails printing the original to make a mask image and combining the original and the mask or masks, in register, to then print.