Color tone control method and apparatus for printing machine

A tone control apparatus in a printing machine which comprises:

• an ink key control means for controlling an ink key opening in said printing machine;
• an ink source roller control means for controlling an ink source roller rotation speed;
• an upstream digital data memory for storing process data made at an upstream;
• a spectral reflection rate data memory for storing spectral reflection rate data measured from a sample printed by said printing machine;
• a calculation unit;
• and
• a control apparatus for instructing said ink key control means and said ink source roller to control said tone,
• by making said calculation unit calculate dot area rate along a paper transport direction per a width of said ink key on the basis of said upstream digital data,
• making said calculation unit execute a selective integral and averaging of said dot area rate calculated on the basis of said process data stored in said upstream digital data memory and said dot area rate in an actually printed matter along said paper transport direction per said with of said ink key,
• making said calculation unit calculate control quantities such as said ink key opening and said ink source roller rotation speed in said printing machine, on the basis of said dot area rate and said spectral reflection rate obtained by said selective integral and averaging.