An optimal diagnostic quality radiograph is defined as one that is:

An optimal diagnostic quality radiograph is best defined as one that is always within acceptable limits. This definition encompasses several essential factors that contribute to a quality image in radiology. These factors include proper exposure settings, appropriate positioning of the patient, adequate contrast, and resolution. When a radiograph falls within acceptable limits, it ensures that the image will provide the necessary diagnostic information without being excessively overexposed or underexposed, which could hinder the visualization of anatomical structures or pathological conditions.

The idea of being "within acceptable limits" acknowledges that while perfection in radiographic quality is desirable, it is often impractical to achieve perfect images in every scenario due to various variables in clinical practice. Acceptable limits allow for slight variations while still ensuring the diagnostic utility of the image.

This definition is more encompassing and practical compared to the other options. For instance, while enhancing images with digital processing can improve quality, it is not necessary for a radiograph to be classified as having optimal diagnostic quality. Similarly, an image that is always easy to interpret or perfectly exposed without any artifacts does not consider the variability in clinical settings and the importance of maintaining sufficient diagnostic information within acceptable standards.