{'fraction_non_alphanumeric': 0.033003300330033, 'fraction_numerical': 0.015841584158415842, 'mean_word_length': 4.512727272727273, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
5. Factors Affecting MTFs of Screen-Film Systems

The MTFs and LSFs of screen-film systems include several image-degrading components. For many decades, the light diffusion in the screens was considered to be the cause of unsharpness in screen-film systems. The light diffusion in the screens includes the transmission of emitted phosphor light via reflection, refraction, scattering, and absorption processes in a phosphor layer which is made up of phosphor particles and a plastic binder coated on a base. It has been found generally that the thicker the phosphor layer, the greater the light diffusion, and thus the greater the unsharpness. One should note, however, that thick screens are commonly employed for the purpose of increasing the sensitivity or speed because the x-ray absorption in the screens is increased. The light reflection or absorption layer coated on the base is also known to be a factor affecting both the unsharpness and the speed of screen-film systems. Therefore, for screen-film systems which consist of the same film and of screens made of the same phosphor, the faster the screen-film system, the lower the MTF will be in general, as illustrated in Figure 5.1. Here the MTFs of four screen-film systems (3M Trimax 2, 4, 8, and 12 screens combined with Kodak OG film) were measured at 80 kV. The relative speeds of Trimax 2, 4, 8, and 12 with OG film were approximately 1.0, 1.5, 2.8, and 4.1, respectively. Other factors affecting the MTF of a screen-film system are described below.