An image reading apparatus, including an image sensor configured to
receive light and output an image signal in accordance with image data
carried in the light, an A/D converter configure to convert the image
signal into a digital signal with reference to a reference voltage, and a
reference white plate configured to be read so as to generate density
data. Also included is a correction device configured to correct the
digital signal in accordance with shading data, a reference member
configured to define a readable density limit, and a detection device
configured to detect a ratio of density of the reference white plate to
that of the reference member as density adjustment data. The density is
obtained by reading the respective reference member and reference white
plate in substantially a same exposure condition. Further included is a
control device configured to control the correction device to adjust the
digital signal in accordance with the density adjustment data.