Magnetosphere of Earth: Waves

An optimum drive energy for a print head is supplied over an extended period of time to provide consistently good image quality without troublesome operation by the user. Temperature of the print head is monitored while varying the drive energy. A threshold value of drive energy required for ink ejection is judged using the drive energy and temperature data. An optimum drive condition is determined on the basis of the threshold value and, when the determined drive condition is different from drive condition information stored in the ink jet print head, the drive energy supplied to the ink jet print head is changed.