Photographic developer

摘要

A black and white developer solution containing o- or p-N-(2-hydroxyethyl)aminophenol as developer substance and a piperazine derivative of the formula <IMAGE> in which R1, R2 and R3 denotes substituents as described hereinafter capable of developing a certain quantity of film e.g. 10 roll films per liter successively to substantially constant gamma values.