Image reading apparatus having improved shading correction and quantity of light ratio measurement.

摘要

An image reading apparatus for reading an image on film which uses a shading correction coefficient computation unit for obtaining a shading correction coefficient in order to correct irregularities in image signals of a photoelectric conversion unit, and a quantity of light ratio measurement unit for obtaining the ratio of the quantity of light of each emission color in order to equalize the quantity of light emitted by a light emission unit. The shading correction coefficient and the quantity of light ratio are obtained immediately before reading of a first original medium, and additional original mediums can then be read using the correction coefficients obtained for the first original. Alternately, the shading correction coefficient and the quantity of light ratio can be obtained immediately before reading each original medium.