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There direct x-ray films and three geometric conditions were used to study the effect of noise and sharpness on high resolution radiography of the hand. The wiener spectrum of film graininess and the MTF of geometric unsharpness were measured. Radiographs of a wire mesh and a hand phantom, together with the Wiener spectra and MTFs, led to the following conclusions regarding fine-detail skeletal radiography, as currently employed: 1) bone structure detectable in vivo does not show minute structural detail; 2) the technique is primarily noise-limited; 3) the use of better geometry or finer grain film for improving resolution or noise is of limited practical value, whereas the use of poorer geometry or more noisy film results in appreciable degradation of skeletal images; and 4) the present standard technique for in vivo radiography of the hand, therefore, may by very nearly optimal for clinical applications.

The possibility of using neon lines excited in a hollow cathode discharge tube for obtaining wavelength calibrations in infrared is explored. The problems involved in making use of these lines for obtaining the relative positions of the rotational lines in vibration rotation bands are discussed. The identifications of the higher order neon lines observed with a 2000-line/in. grating are made available.

When radiographic film is exposed with fluorescent intensifying screens, the spatial x-ray quantum fluctuations are recorded on the film in the form of density fluctuations (“quantum mottle”). The x-ray quantum fluctuations can be regarded as the input and the quantum mottle as the output of the image-forming system. The Wiener spectrum of the quantum mottle has been used to determine the relative modulation transfer function of two radiographic systems.

A method has been devised for measuring the line spread-function of medical radiographic systems by means of a 10-μ slit with uranium jaws. It has been shown theoretically that the inherent error introduced by the finite width of the slit is negligible because the screen–film systems are of poor optical quality. Line spread-functions of two typical systems have been measured. From one of these, the intensity distribution in the image of a uranium edge has been calculated and found to agree with the measured distribution.