Thanks for sharing this introduction to radiographic testing. A few points worth highlighting for members working with RT:

Key differences between X-ray and gamma radiation:

X-ray sources are electrical devices that you switch on and off, which gives you control over exposure time and intensity. Gamma sources are radioactive isotopes (cobalt-60 and iridium-192 are common in industry) that emit continuously, so they require careful handling, storage and decay calculations. Gamma is often chosen for site work and pipe inspection because the sources are compact and need no power supply.

Both produce penetrating radiation that's absorbed differently by materials of different densities and thicknesses — that's what creates the image contrast on film or digital detector. The thicker or denser the material, the less radiation reaches the recording medium, so it appears lighter on the radiograph.

For interpretation:

The quality of the radiograph depends on exposure settings, the recording medium (film speed, digital detector sensitivity), geometry and film processing. A radiograph shows a 2D shadow image of a 3D object, so you need to understand what you're looking at: is a dark area a void or a thickness change? This is why procedure, reference standards, acceptance criteria and the responsible Level III inspector are essential.

Members interested in RT technique and interpretation might also want to check the Radiography group forum for discussions on exposure calculations, IQI selection, film density and defect identification — or post specific questions there.