Dependence on \mant of the photonuclear cross section for the coherent photoproduction of $\Jpsi$ off Pb compared with model predictions  (top panel), where for LTA the {\em low shadowing} case is shown (see text). Model to data ratio for each prediction in each measured point (bottom panel). The uncertainties are split to those originating from experiment and to those originating from the correction to go from the UPC to the photonuclear cross section.