An aberration correcting plate for a compatible interchangeable lens which can be detachably attached to a first camera body having a large resultant thickness of filters provided in front of an image pickup device and to a second camera body having a small resultant thickness of filters provided in front of an image pickup device is mounted to a rear end of the compatible interchangeable lens when the rear end is mounted to the second camera body. The aberration correcting plate is made of a parallel-plate whose refractive index N is greater than 1.7 or a lens of negative power. The sum of the thicknesses of the aberration correcting plate and the filters provided in front of the image pickup device of the second camera body is substantially identical to or smaller than the total thickness of the filters provided in front of the image pickup device of the first camera body.