Pendellösung fringes obtained from x-ray diffraction section topographs are sensitive to elastic strain lower than 10-6. The strain sensitivity is higher for topographs taken with a diffraction vector closer to the lattice displacement vector. This effect is demonstrated in two types of samples: 1. (1) a Si(111) wafer with an epitaxial Pd2Si thin film and naturally present strain, and 2. (2) a triangular shaped Si(111) crystal with an artifical strain field produced by one point bending.