an image reading method and apparatus . a reader is mounted and reads one side of an original document being conveyed at a reading position . a contact glass includes a surface contacting the original document . a reference is disposed at a side of the contact glass opposite to the surface and movable between the reading position and a standby position . the reference includes a surface facing the reader which has a predetermined color for providing shading data used for a shading correction . a carrier moves the reference to the reading position . the reader obtains the shading data by reading the predetermined color on the surface of the reference at the reading position .