A system for adjusting a selected operating parameter of an image forming device to control white vector based on selected environmental conditions includes an image forming station having a photoconductive surface with a latent image formed by discharged areas leaving non-discharged areas different from the discharged areas, a sensor mechanism for measuring selected environmental conditions of dry-bulb temperature and relative humidity, a control mechanism for reading the sensor mechanism to adjust the voltage bias of a charging unit by an offset applied to the charging unit based on a wet-bulb temperature value so as to minimize white vector without enabling onset of development of toner background on non-discharged areas, and a memory connected to and accessible by the control mechanism and storing a lookup table of a list of wet-bulb temperature values related to measured dry-bulb temperature and relative humidity values and correlated to a list of voltage bias offsets.