A method calibrating a thermal print head printer having fixed imaging elements so that consistent high resolution output may be achieved includes a means for measuring a common characteristic of each fixed imaging element and storing the values so that print head compensation may occur during the printing process one scan line at a time. Error diffusion, either across the thermal print head, down-web, or both, ensures that appropriate drive level are supplied to each fixed imaging element regardless of inherent differences in the common characteristics of the fixed imaging elements, to achieve consistent tonal image quality. In a preferred embodiment, the fixed imaging elements are thin film electrical resistive elements and the common characteristic is the electrical resistance of the thin film resistor elements.