Background evaluation and spot recognition on crystallographic diffraction photographs

A computer method is described which provides a means for determination of both background and spot characteristics without the knowledge a priori of the positions of those spots in a crystallographic diffraction photograph. The background is first determined in any arbitrary region by means of a histogram technique. Then the sets of points emerging from the background's statistical tolerances are collected together with simple neighbouring rules. The problem of large areas which do not fit in a computer memory is discussed and solved with an overlapping window technique. The accuracy of the method is checked by means of a simulation (characteristic retrieval of computer generated spots); the precision appears to be better than the classical rectangular box method except for weak spots.