1. An image sensor having an image pixel array with a plurality of rows and columns, wherein the image pixel array comprises: a plurality of phase detection pixel pairs that gather phase information, wherein each of the phase detection pixel pairs comprises first and second photosensitive regions, wherein the first and second photosensitive regions are covered by a single microlens, wherein each microlens has a length, a width, and a height, wherein the length is longer than the width, and wherein the phase detection pixel pairs are arranged in a dashed line in a single row of the plurality of rows; and a plurality of image pixels that each have a symmetric response to incident light, wherein the dashed line comprises at least one image pixel interposed between each phase detection pixel pair.