From top to bottom row: orbital inclination is 65°, 25° and 0°. Left column: standard deviation of the column density at inferior (resp. superior) conjunction in red (resp.blue) as a function of the ratio . Each couple (a, β) leads to a different proportionality constant between δN_H and , hence the large dispersion. The dashed line in the top left panel indicates the y = x line. Right column: same as before but R_cl,2 has been replaced by the clump radius at the point along the LOS between the X-ray source and the observer the closest from the donor star. The dispersion is reduced, especially at inferior conjunction.