1. A method comprising: obtaining, by a computing device, a plurality of images of a scene, wherein the plurality of images were captured by an image sensor, and wherein the plurality of images includes a first image and a second image, wherein a particular gain has been applied to the first image; determining an effective color temperature and a brightness of a first pixel in the first image; based on the effective color temperature and the particular gain, selecting a mapping between pixel characteristics and noise deviation of the image sensor, wherein the pixel characteristics include pixel brightness; using the selected mapping to map at least the brightness of the first pixel to a particular noise deviation; comparing the brightness of the first pixel and the particular noise deviation to a brightness of a second pixel of the second image; and based on the comparison, determining whether to merge the first pixel and the second pixel.