Controller for photographic enlarger or the like

Apparatus for controlling a photographic enlarger in accordance with a predetermined set of reference values for color and density with the enlarger having a light source capable of radiating light of different wavelengths comprising:

• means for sensing a number of different wavelengths of the light from said light source, said sensing means being operable to generate a voltage corresponding to the amount of light of each of said number of wavelengths, respectively;
• a timer;
• means coupled with the timer for applying a voltage to the enlarger for energizing the same during a period in which the timer is actuated;
• means coupled with the timer for adjustably setting the timer to any one of a number of different time periods;
• a summing device for each of said number of wavelengths, respectively, each device having a number of inputs and an output, each device being operable to provide a null condition at the output thereof when the sum of the input voltages is substantially zero, said sensing means corresponding to each of said number of wavelengths being coupled to one of the inputs of the respective device, said time setting means having means coupling it to another input of each device, respectively;
• means coupled with a third input of each device, respectively, for applying reference density and wavelength voltages thereto in accordance with said predetermined reference set;
• and means coupled with the output of each device, respectively, for indicating a null condition of the output thereof.