What is the major tool of quality control for daylight systems?

The major tool of quality control for daylight systems is preventive maintenance. This approach is essential because it focuses on regular inspections and maintenance activities designed to prevent equipment failures before they occur. In the context of radiography, especially with daylight systems, ensuring that the equipment is functioning optimally is crucial to maintaining the quality of the radiographic output. Preventive maintenance can include routine cleaning, checking for wear and tear, and making necessary adjustments to the equipment. By prioritizing these proactive measures, operators can minimize the risks of defects in the radiographic process, thereby ensuring the reliability of the results produced.

In terms of other options, radiographic testing, while important for evaluating the quality of images produced, is typically considered an assessment technique rather than a proactive control measure. Calibration procedures are crucial but are often part of the broader maintenance strategy rather than being a standalone tool for ongoing quality control. Quality audits focus on reviewing processes and outcomes to ensure compliance and effectiveness, rather than directly maintaining the equipment's operational capabilities. Thus, preventive maintenance stands out as the most direct and critical tool for ensuring quality in daylight systems.