An imaging apparatus comprising: a conversion unit comprising a plurality of unit-pixels for converting an incident radiation transmitted through an object or a light generated based on the incident radiation into pixel information; a controlling unit for controlling a driving of said conversion unit according to a plurality of operation modes; and a signal processing unit for, based on the controlling by the controlling unit, reading the pixel information for individual unit-pixels in a unit pixel-reading mode among the plurality of operation modes, and for reading by adding the pixel information for multi-pixels in a multi-pixel reading mode among the plurality of operation modes, characterized in that the imaging apparatus further comprises: a storage unit for storing unit-pixel defect information including position information of a defective unit-pixel related to the unit-pixels extracted by comparing, with a first threshold value, the pixel information for the unit-pixel obtained by irradiation of said conversion unit with the radiation or the light under a condition without the object and multi-pixel defect information including position information of a defective multi-pixel related to the multi-pixels extracted by comparing, with a second threshold value, the pixel information for the multi-pixel obtained by irradiation of said conversion unit with the radiation or the light under the condition without the object and by adding a plurality of pixel information of the unit-pixels; and a correction unit for performing a correction of the information of the unit-pixel in the unit-pixel reading mode-based on the position information of the defective unit-pixel related to the unit-pixels, and performing a correction of the information of the multi-pixel in the multi-pixel reading mode based on the position information of the defective multi-pixel related to the multi-pixels. a conversion unit comprising a plurality of unit-pixels for converting an incident radiation transmitted through an object or a light generated based on the incident radiation into pixel information; a controlling unit for controlling a driving of said conversion unit according to a plurality of operation modes; and a signal processing unit for, based on the controlling by the controlling unit, reading the pixel information for individual unit-pixels in a unit pixel-reading mode among the plurality of operation modes, and for reading by adding the pixel information for multi-pixels in a multi-pixel reading mode among the plurality of operation modes, characterized in that the imaging apparatus further comprises: a storage unit for storing unit-pixel defect information including position information of a defective unit-pixel related to the unit-pixels extracted by comparing, with a first threshold value, the pixel information for the unit-pixel obtained by irradiation of said conversion unit with the radiation or the light under a condition without the object and multi-pixel defect information including position information of a defective multi-pixel related to the multi-pixels extracted by comparing, with a second threshold value, the pixel information for the multi-pixel obtained by irradiation of said conversion unit with the radiation or the light under the condition without the object and by adding a plurality of pixel information of the unit-pixels; and a correction unit for performing a correction of the information of the unit-pixel in the unit-pixel reading mode-based on the position information of the defective unit-pixel related to the unit-pixels, and performing a correction of the information of the multi-pixel in the multi-pixel reading mode based on the position information of the defective multi-pixel related to the multi-pixels. a storage unit for storing unit-pixel defect information including position information of a defective unit-pixel related to the unit-pixels extracted by comparing, with a first threshold value, the pixel information for the unit-pixel obtained by irradiation of said conversion unit with the radiation or the light under a condition without the object and multi-pixel defect information including position information of a defective multi-pixel related to the multi-pixels extracted by comparing, with a second threshold value, the pixel information for the multi-pixel obtained by irradiation of said conversion unit with the radiation or the light under the condition without the object and by adding a plurality of pixel information of the unit-pixels; and a correction unit for performing a correction of the information of the unit-pixel in the unit-pixel reading mode-based on the position information of the defective unit-pixel related to the unit-pixels, and performing a correction of the information of the multi-pixel in the multi-pixel reading mode based on the position information of the defective multi-pixel related to the multi-pixels.