Various techniques are provided to perform flat field correction for infrared cameras. In one example, a method of calibrating an infrared camera includes calibrating a focal plane array (FPA) of the infrared camera to an external scene to determine a set of flat field correction values associated with a first optical path from the external scene to the FPA. The method also includes calibrating the FPA to a shutter of the infrared camera to determine a set of flat field correction values associated with a second optical path from the shutter to the FPA. The method also includes using the flat field correction values associated with the first and second optical paths to calculate a set of supplemental flat field correction values to apply to thermal image data obtained with the infrared camera. The method also includes storing the supplemental flat field correction values.