(Upper left and lower left) Horizontal and vertical slices through the reconstructed focal intensity (Dataset 1), obtained by numerical propagation of the reconstructed complex illumination 5 mm upstream and downstream of the reconstruction plane. The vertical slit S1V was opened here to 0.2 mm, whereas the horizontal beam-defining slit S1H was opened to 0.1 mm, only half as wide. Accordingly, the focus is wider in the horizontal direction owing to the smaller numerical aperture. Note the indication of several distinct planes which correspond to the nominal plane of the pinhole P2 (see Fig. 1), the reconstruction, i.e. the sample plane, as well as the focal plane as determined by a numerical focusing criterion (see main text). (Upper right and lower right) The one-dimensional profiles of intensity (black) and phase (red) on the right correspond to the latter plane and indicate the asymmetry of the focus with respect to the horizontal and vertical directions. Both are selected such that they share the pixel of highest intensity in the two-dimensional intensity distribution.