nd FIG. 6(c) is a view showing the data collection position on thereference density plate.In the present embodiment, an example when there is an abnormality in the first shading correction data, will be described, however, it is the same as in the case of the second shading correction data.In FIG. 4, and FIGS. 6(a) 6(c), the analog output from the CCD image sensor 19 read out at the first collecti