Collecting samples to adjust a signal includes providing a shutter in an opened position to allow a detector of an infrared camera to detect infrared radiation and generate a signal corresponding to the infrared radiation. A first touchup iteration is initiated by moving the shutter to a closed position, and samples of a reference frame are collected according to a collection instruction. The shutter is then moved to the opened position. If there is a change in a state of the infrared camera, the collection instruction is adjusted in response to the change. A second touchup iteration is initiated by moving the shutter to the closed position, and samples are collected according to the adjusted collection instruction. A modification of the signal is determined in accordance with at least some of the samples.