The International Institute of Welding (IIW) patterns used are radiographs of carbon steel weld beads and the radiographic parameters employed (the tension of the apparatus, the current applied, existing type of weld, focal distance, etc.) are given for each film, although these factors were not taken into consideration as they do not make part of the work proposed. In this study, only the IIW radiograph patterns were used as they have good quality of image (good
contrast and low density) and reliability in terms of technical reports given for each film.
Although there are scanners such as the Agfa RADView FS 50, ideal for high-density films, due to the high quality of the films, a low-cost scanner, a UMAX, Mirage II model (3.0 maximum optical density; with 2000 dpi (dots per inch) of maximum resolution for films) was used for the digitalization of the radiographs, following the ASME V [16] norms. The resolution employed was 500 dpi, giving an average size (due to a small variation in the film sizes) image of 2900 pixels (horizontal length) £ 950 pixels (vertical length), which resulted in an average pixel size of 50 mm. This resolution was adopted as it permitted the detection and measurement of defects of sizes in the order of hundredths of an mm, which in practical terms of radiographic inspection is well above normal. The resol-ution in tones of gray chosen was eight bits (256 levels), which was the maximum for this model of scanner and images with 10, 12 or 16 bits are in terms of space rather
large also man is visually incapable of noting the difference of gray tones above 128 levels.