This article is a review of the short notes by the author published in Acta Cryst., A29, 724 (1973) and ibid., A30, 600 (1974) . The method for the accurate determination of low order structure factors from the thickness fringes in electron micrographs are described in more detail. Applications to magnesium oxide, silicon and cadmium sulfide are given. For cadmium sulfide, which is a non-centrosymmetric crystal, the phase angle of the crystal structure factor was determined as well as the absolute value.