Incorporated coupler tripack dyes.

All dyes fade in time but some are far more prone to fading than others are. Many Magenta dyes used in integral tripack films are azomethines and are very stable, whereas many Yellows and Cyans fade easily. The degree of fading of integral tripack dyes is directly related to the original quantity present and generally the dyes fade to colourless rather than change colour. The visual effect is therefore to reduce the maximum density of the fading dye and reduce its visual contrast resulting in a change in colour balance and the effect known as crossed curves. Many films go Magenta, as the magenta dye is least or not at all effected.

This proportional fading provides possible mechanisms for correcting the effect.

It is helpful to find out the degree of fading in a film. This can be done with a densitometer providing there is in existence a piece of unfaded film of the same stock and period. Select images of maximum density and compare the R, G, B densities on the assumption that the faded film originally had similar maxima to the unfaded. This technique is useful and easy to apply to some faded prints of the 1960’s and 70’s since fading of this period is often due to poor stabiliser formaldehyde concentrations and therefore unfaded, well processed film of the same period is usually easy to locate.

In the case of many print films that are pale and strongly visually magenta, another opportunity for measuring the degree of fading exists. It can be assumed that the magenta has not faded at all [this is never absolutely true but still useful as a premise].

Select a maximum density area and measure the Status A values. It can be assumed that the original densities were more or less equal or visually neutral.

In above case the percentage fading of a cyan dye can be calculated from the formulae % Fading of Cyan dye = Dgreen - Dred x100 Dgreen