American Society for Nondestructive Testing (ASNT) Radiographic Testing Practice Test

A larger source size decreases the sharpness of the radiographic image. This reduction in sharpness occurs because a larger radiation source leads to greater geometric unsharpness. When the source of radiation is larger, the X-rays emitted from different points within the source create a spread of rays that can overlap when they reach the film or digital detector. This resultant overlap causes a blurriness around the edges of features in the image, leading to a loss of definition.

In contrast, a smaller source size minimizes this effect because the rays originate from a more concentrated point, allowing for more precise imaging. This principle is essential in radiographic testing, as sharpness directly influences the ability to identify defects or discontinuities in materials being tested. Thus, the impact of source size on image sharpness is a critical factor in ensuring quality in radiographic inspections.