To combine with the original when printing a colour internegative or intermediate.

In this case, the mask can be black and white in order to correct contrast [an unwieldy technique almost never used since flashing or development control is easier] or a coloured mask in order to correct for faded dyes. This last technique was a very effective and relatively simple procedure that has not been carried out for some years. Two techniques are described by C. Bradley Hunt in SMPTE 1981. One is very complex, the other easy and sophisticated.

In the Flashed Dupe Mask Method a positive print of a faded original [usually a positive] is made on a colour reversal print film to a colour balance and contrast more or less complimentary to the faded image. For example, a faded colour print is often magenta due to the fading of the yellow and cyan. The mask would be visually green in this case, with a low green contrast, produced by flashing the print film. When combined in register the three contrasts can be equalised, and the process is easy to control without sophisticated sensitometry since the combined mask and original will appear neutral or “correct” in balance when the mask is correct. From the combination of the mask and the original, a colour internegative or intermediate can be made.

This procedure is easy to operate although making the mask may need some trial and error printing. Dyes can be corrected when the contrast reduction is up to 30%.

The process is hardly used today because the majority of the need is to restore 35mm and 35mm reversal processes do not exist in commercial laboratories. The technique could be used for 16mm restoration [for example of faded news film] but has not been used so far.

The Dupe Mask Method is far more complex but can correct up to 50% dye fading.