Maps of the contrast c_Ne (Eq. (13)) between column density computed by synthesis of white-light images and the actual column density from the MHD simulation under two different assumptions: a) all emitting plasma is located on the plane of sky; b) all emitting plasma is located at the distance from the plane of sky computed by the polarization ratio technique. The white contour roughly identifies the flux rope position where the ratio between the y component of the magnetic field integrated along the LOS divided by the magnetic field intensity is above the arbitrary positive threshold of 0.4.