1. An imaging system comprising: an image sensor comprising a pixel array for sensing electromagnetic radiation, the pixel array comprising: a plurality of pixel groups comprising only active pixels, and a plurality of pixel groups comprising only optical black pixels; and a plurality of line readouts, wherein each line readout is configured to read out a single group of the plurality of pixel groups in the pixel array, wherein the imaging system samples one or more of the plurality of pixel groups comprising only optical black pixels a plurality of times to reduce a size of the image sensor by reducing a number of optical black columns.