title: Determination of radiographic screen-film system characteristic curve and its gradient by use of a curve-smoothing technique.
abstract: One of the important factors affecting radiographic image quality is the film contrast of the recording system, which may be expressed by the gradient of its H & D curve. Experimental determinations of H & D curves are subject to relatively small error, which can nevertheless cause large fluctuations and uncertainties in the calculated gradient. To reduce this fluctuation, we wrote a computer program for orthogonal-polynomial (discrete  Legendre polynomials) curve fitting by means of least-squares estimation of parameters. This procedure facilitates curve smoothing and gradient computation following sensitometric measurements. The program was tested against a large number of measured characteristic curves. A brief description of the program is given, with examples which illustrate its applications.
mesh_terms: D008433:Mathematics; D011859:Radiography / Q000295:instrumentation; D012044:Regression Analysis; D013679:Technology, Radiologic