The Superadditivity of Phenidone and Metol in Diffusion-Transfer-Colour-Development

Abstract

In contrast with the experiment by Mason1) who showed the superadditivity of Phenidone and Metol on ordinary colour development of an iodo-bromide emulsion layer using soluble couplers in the developer, in our experiments using an ordinary colour developer and a diffusion-fast coupler in a chloro-bromide emulsion layer, Phenidone shows no activation on colour densities and only a little activation on silver deposits. On the contrary, however, profound increase of sensitivity and densities (both colour and silver) are shown on negatives and also significant increase of apparent speed and dramatical reduction of fog level are shown on positives of diffusion-transfer colour development by the introduction of Phenidone (or Metol) in the developer. And it is concluded that the marked effect observed comes from the enhanced efficiency of the repeated use of the regenerated Phenidone (or Metol) by the restriction of the volume of the developer involved in this closed system.