The blur of images in layer radiography is analyzed in the spatial frequency domain in which many problems of radiographic system are treated. The types of layer radiography treated here are Tomography, Planigraphy and Circus Tomography. In each case, single and multi-layer radio-graphies are studied. The line or point spread intensity distributions, on layer radiographs, from the focus of X-ray tube and their Fourier transforms are studied theoretically and experimentally. Further the optical transfer functions of image intensifying screens and films in the case of oblique incident X-ray are investigated. From these experimental results, the author suggests a few im-provements both in the part of X-ray sources and in the part of intensifying screens and films.