Imaging apparatus, an imaging apparatus main body and shading correction method

If the correction table corresponding to the imaging conditions of the lens unit 50 mounted is not stored in the lens information memory 141, the correction table corresponding to the set imaging condition is calculated and stored in the lens information memory 141. Thereafter, if the lens unit 50 is mounted again set the same photographing conditions, shading of the main image, sub-image correction table corresponding to the imaging conditions of the lens unit 50 is corrected.