for fully resolving a pair of lines (one black, and one white), 2 rows of pixels should be used, right? Nope, 4 rows needed because of Bayer pattern: blue,green,blue,green. so in matter of resolution, 4k is not actually 4k, let alone 1080p. so 2 megapixel Sigma Foveon like sensor (3 layered color filter), has potential to be equal to bayer 4k. BUT, its insane to make 2 megapixel Full Frame sensor, cause every single one of pixels will have a massive area, almost 17um x 17um. that will heavily suffer from electron overflowing, and you need a thick dark ND filter for your every outdoor shot. what we lack right now, is not resolution. we lack Acuity. colors are not correct, much of that is based on mathematical guess, thanks to demosaicing, edges are soft for exactly same reason. lots of moire and false data. 4k isnt going to solve all of these, but downscaling, a decent downscaling, can give us some of that acuity we are lacking right now. the problem is, there is no camera equipped with "Built-in Best-in-Class hardware-accelerated downscaler". all the processing is on your own (PC) shoulder. otherwise, why should I care if gazillion pixels has been read out to give me my sweet 1080p?