At least one exemplary embodiment is directed to a radiography apparatus configured to have an offset reading period, where during the offset reading period an offset reading operation is performed without illumination by radiation (e.g., X-rays). The offset reading period can be different from a radiation (e.g., X-ray) reading period in timings of applying a gate pulse. During the offset reading period, a pixel addition can be performed such that the switching elements corresponding to two or more lines are concurrently turned on-off thus reducing the offset reading period.