A new method is presented to determine from top views whether a tabular silver halide crystal contains an even or an odd number of twin planes. The model is based on the occurrence of diffuse intensity contours in diffraction patterns of the crystals. This implies that this information can be correlated with simultaneous observations of the shape of the tabular crystals (hexagonal or triangular). Moreover, it will be shown that this method allows one to determine from top views in which variant of an even twinned crystal dislocations are present.