Abstract: Apparatus is provided for obtaining optimal development of photothermographic paper at different paper speeds and with intermittent paper movement. This is accomplished by a heater platen with plural heaters which are selectively energized in accordance with a function of paper speed. Also a fan for cooling of the platen is selectively energized in accordance with temperature. For this purpose, a temperature signal is produced corresponding to the temperature of each heater and, a speed signal is produced corresponding to the paper speed; if desired, a contrast signal can be produced corresponding to the degree of contrast desired in the development of the paper. A logic device, preferably a microprocessor operating under a program control, processes the signals and controls the energization of the heaters and the fan. More particularly, the platen is heated by plural electrical resistance heaters and is provided with a temperature sensor for each resistance heater.