An automatic data collection device is provided with an aiming beam that can be deactivated prior to reading a target machine-readable symbol. The data collection device includes a sensor that generates one or more signals associated with light received by the sensor. The sensor signal(s) is used to adjust the illumination levels for the sensor and/or the gain of the sensor, and are also used to deactivate the aiming beam prior to reading the target machine-readable symbol or to perform other illumination adjustment.