An image sensor may include an array of image photodiodes formed in rows and columns. The array of image photodiodes may include a region of photodiodes arranged in three adjacent rows and three adjacent columns of the array. The region of photodiodes may include four non-adjacent photodiodes, each of which generates charge in response to the same color of light. The four non-adjacent photodiodes may be coupled to a shared floating diffusion node. Each of the four non-adjacent photodiodes may transfer generated charge to the shared floating diffusion node. The charges from each of the four non-adjacent photodiodes may be summed at the shared floating diffusion node and read out as a summed signal or may be individually transferred to the shared floating diffusion node and read out individually.