INTEGRAL MASKING.

Although the dyes used in modern integral tripacks are called Cyan, Magenta and Yellow, they are not perfect, and this leads to some problems. When one film image is duplicated onto another, the imperfections in the dyes compared with the ideal subtractive primary colours, characterised as unwanted absorptions, are duplicated, reducing the colour saturation of the final prints. As multiple generations are produced, so the problems of colour saturation are increased. This problem can partially resolved in reversal materials only by complex chemical adjustments to dye formation that takes place in development called inter-image effects. In negative positive systems, almost complete correction is possible in the negative stage by the use of integral masking.

The unwanted green and blue absorptions of the cyan dye image print through onto the green and blue sensitive layers of the duplicating stock. This is equivalent to a small pink impurity in the cyan dye image.

The unwanted blue absorptions of the magenta dye image prints through onto the blue sensitive layer of the duplicating stock. This is equivalent to a small yellow impurity in the magenta dye image.

The yellow dye image is satisfactory and needs no change.

These impurities vary in density with the density variations of their own dye images, so producing actual print through images in the duplicating stock.

If these impurities of pink and yellow in the dye images are balanced exactly with amount of pink and yellow in the unexposed parts of the emulsion. This produces an overall pink/yellow cast to the film, but no print-through images, then the pink/yellow, (or orange) cast can be filtered out in printing to produce correct colour balanced duplicates, without print-through images from the unwanted dye absorptions.

To achieve this the colour couplers in the cyan and magenta dye layers, which are used to form the dye images in exposed and developed image areas, are themselves coloured pink and yellow respectively. Once a coupler becomes part of the dye image, it loses its own original colour.

Thus, in areas with no dye formation, there is a strong orange mask colour present, and in areas where cyan and magenta dyes form, the orange mask disappears to balance out the unwanted dye absorptions now present. The result is known as an Integral mask and is used in all colour negative and intermediate film stocks, to retain good colour reproduction through multiple duplication stages.

Integral masking has made restoration simpler, since once a colour image is recorded on a masked film several integral masked stages of duplication can be undertaken without excessive loss of colour quality. Duplication using unmasked films loses some of the original hues and contrasts in just a single generation.