MTF Resolution Of Images Obtained Without An Acquisition System.

The present paper proposes an extension of the traditional evaluation of the MTF curves in the case in which the acquisition system is not available and the input is not well known, if a relatively low quality of the result is accepted. The method is at first applied when only the acquisition system is unknown, and then when also the input is not well known; in this case the face and the right hand of the Turin Shroud are studied underlining the relatively high resolution of such images in comparison with other examples. The method is applied to images of the Turin Shroud and to images obtained both by means of PP (Psychic Photography) and BEO-GDV (Biological Emission and Optical radiation - Gas Discharge Visualization). While the resolution of the Shroud images reaches 4.9±0.5 mm at the 5% MTF value, that of PP image is only 12±2 mm, but the resolution of BEO-GDV images of 5.3±0.3 mm is compatible with that of the Shroud images. It results an anomaly at the low spatial frequencies (less than about 20 m-1) that clearly presents values less than the unity. If verified with future studies, this data would set a new interesting characteristic of the Shroud image: the “acquisition system” should be characterized by the fact that the spatial frequencies around 30 m-1 are better represented than the others.