{'fraction_non_alphanumeric': 0.020689655172413793, 'fraction_numerical': 0.0, 'mean_word_length': 5.160377358490566, '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}}
Effects Of Modulation Transfer Function (MTF) And Phase Transfer Function (PTF) On Visual Performance

This paper provides a summary of results and conclusions of work, to be published in full elsewhere, on visual performance related to system design and assessment. The system transfer functions, MTF and PTF, are widely used, nowadays, for characterising the quality of many classes of imaging system. The aim of the present work is to provide an interpretation of these transfer functions which is relevant to the visual performance of an observer when viewing the output of the systems. Measurements were made of visual contrast discrimination and of phase threshold levels. In both cases, attempts are made to derive general conclusions, since these tend to be more useful for system design and evaluation. From the experiments, a tolerance is derived for MTF measurement and assessment, so enabling MTFs of different designs, or determined by different techniques, to be directly compared. Results presented on the sensitivity of the visual system to changes in phase suggest that the PTF need not be considered for well-designed and constructed systems. Thus, phase threshold levels are small only at low spatial frequencies: the region where phase shifts in imaging systems are usually negligible.