When photo timing is not available for infant radiography, technique charts should be based on patient:

In the context of infant radiography, using technique charts based on patient size is the most appropriate approach when photo timing is not available. This is because size more accurately reflects the body's dimensions and composition, which directly influence the amount of radiation required to produce a quality radiographic image.

Infants vary significantly in size compared to older children or adults, and their smaller body structures, such as the thoracic cavity and density of surrounding tissues, require careful consideration to optimize exposure settings. While weight, age, and height play roles in determining appropriate techniques, size encompasses a more comprehensive consideration of physical body dimensions that are crucial for achieving the desired photographic quality while minimizing radiation exposure.

Using size as a primary factor ensures that the radiographer can adjust exposure parameters effectively to account for the infant's unique anatomical characteristics and the varying thickness of body parts being imaged. This approach leads to better quality imaging outcomes and enhanced patient safety.