Now we have obtained the chance to correct the weighting factors which seemed CT images were influenced by it. This weighting factors (called the weight) classified into the following three kinds, the weight A was to cutoff sharp the high frequency domain, the weight B was to cutoff smoothly high frequency domain, and the weight C was intermediate between the weight A and the weight B. Here we investigated how far these weight have produced an effect upon CT images. Results are as follows 1. We observed that the weight A accompained with ringing or undershoot from surrouding a phantom. At the center water CT values of a head phantom decreased in comparison with around phantom. But the weight B had a little CT values lower than the former. Still it noticed clear inclination in case of using together with the compensator material (Conraxin L). 2. We measured MTF of three kinds of CT images to apply star phantom, The results shown that the weight A was superior to low spatial frequency, and the weight B was better high spatial frequency than other.