PHYSICAL AND CHEMICAL-PROPERTIES OF COLOR COUPLERS IN RELATION TO THEIMAGE QUALITY OF COLOR NEGATIVE FILMS

The performance of an imaging system call be characterized by its obje ctive image quality expressed in terms of a signal-to-noise ratio (SNR ) criterion, in relation to its speed. For a model system containing a silver halide emulsion and an image coupler dispersion, the SNR/speed position is mainly an emulsion property. In this paper, we review a s er ies of experiments and model calculations designed to study tire im plications of coupler type and concentration on the mass of developed silver (expressed in number of silver centres and mass per centre), an d consequently the SNR. Experiments have shown that extreme variations in coupler concentrations can significantly alter the maximum value o f SNX. The SNR/exposure curves also vary in shape and position along t he exposure axis as coupler type and concentration nl are varied due t o differences in mass of developed silver at a given exposure. It was round that a fast colour coupling reaction, achieved by high coupler r eactivity and/or concentration, increases the mass of developed silver at a given exposure suggesting that Intent image bleaching image by o xidized developer is the main factor affecting the mass of developed s ilver, and thus SNX. In all, nine different rt couplers were investiga ted in this study.