Dependence of the diffraction contrast on absorption for rod-like defects in SLG crystals. Transmission projection topographs of sample A [regions C and D marked in Fig. 1(a)]. (a) Lang topograph; (b)–(d) synchrotron white-beam topographs. I1(2) is the intensity of the type 1 (2) wavefield, I0 is the initial value of intensity; I1(2) = I0exp[−μ1(2)t], where t is the thickness of the sample.