1. A method of adjusting an exposure for an imaging system, comprising: determining a location for each of at least one instrument end effector within a field-of-view of a camera; determining a region of interest in the field-of-view based on the location for each of the at least one instrument end effector; gathering luminance statistics for the region of interest; computing a measured luminance value from the luminance statistics; and adjusting the exposure in response to a comparison of the measured luminance value with a target luminance value.