Understanding NRT- Reading 1- 2 of 2- Radiogaphic Testing A
Understanding nrt reading 1- 2 of 2- radiogaphic testing a
Understanding nrt reading 1- 2 of 2- radiogaphic testing a
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Definition<br />
Radiographic definition is the abruptness <strong>of</strong> change in going from one density<br />
to another. There are a number <strong>of</strong> geometric factors <strong>of</strong> the X-ray equipment<br />
and the radiographic setup that have an effect on definition. These geometric<br />
factors include:<br />
1. Focal spot size, which is the area <strong>of</strong> origin <strong>of</strong> the radiation. The focal spot size<br />
should be as close to a point source as possible to produce the most definition.<br />
2. Source to film distance, which is the distance from the source to the part. Definition<br />
increases as the source to film distance increase.<br />
3. Specimen to detector (film) distance, which is the distance between the specimen<br />
and the detector. For optimal definition, the specimen and detector should be as<br />
close together as possible. .<br />
4. Abrupt changes in specimen thickness may cause distortion on the radiograph.<br />
5. Movement <strong>of</strong> the specimen during the exposure will produce distortion on the<br />
radiograph.<br />
6. Film graininess, and screen mottling will decrease definition. The grain size <strong>of</strong> the<br />
film will affect the definition <strong>of</strong> the radiograph. Wavelength <strong>of</strong> the radiation will<br />
influence apparent graininess. As the wavelength shortens and penetration<br />
increases, the apparent graininess <strong>of</strong> the film will increase. Also, increased<br />
development <strong>of</strong> the film will increase the apparent graininess <strong>of</strong> the radiograph.<br />
Charlie Chong/ Fion Zhang
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