The present invention relates to an image sensor and to an imaging system comprising the same. The present invention particularly relates to X-ray image sensors and imaging systems. The image sensor according to the invention comprises a pixel array that includes a plurality of active pixels arranged in a matrix of rows and columns, and a plurality of column lines to which outputs of pixels in the same column are coupled for the purpose of outputting pixel signals. The image sensor further comprises readout circuitry that includes a plurality of readout units, each readout unit being configured for reading out a respective column line through an input node of the readout unit. The image sensor is characterized in that the image sensor further comprises capacitive units, such as capacitors, for capacitively coupling each input node to its corresponding column line.