1. A method comprising: determining a color temperature of a first pixel and a brightness of the first pixel, wherein the first pixel appears in a first image that was captured by an image sensor; selecting a mapping between pixel brightness and noise deviation of the image sensor, wherein the noise deviation characterizes error in pixels that have the color temperature of the first pixel, wherein the error is introduced when the image sensor is capturing an image; using the selected mapping to map at least the brightness of the first pixel to a particular noise deviation; and based on the brightness of the first pixel, the particular noise deviation, and a brightness of a second pixel, determining whether to merge the first pixel and the second pixel, wherein the second pixel appears in a second image that was captured by an image sensor.