Printing machine having ductor roller, correction device, and printing machine correction method

A printing machine has an ink fountain, a fountain roller in contact with the ink fountain, a ductor roller, at least an ink transfer roller and a controller configured and programmed to control the ductor roller. For the printing machine, individual graph data gr and its initial values gri, and average g of the graph data over the entire ductor roller and its initial value gi are used to change graph data gr and g during printing so as to cancel errors between measured printed densities and desired printed densities. An adjustment apparatus and method also achieve this task for such a printing machine.