1. A method, comprising: capturing a series of digital images with an image sensor; as the series of digital images are captured, adjusting at least one parameter of the image sensor selected from the group consisting of exposure time and gain to adjust a mean intensity value of the digital images until a target mean intensity value is reached; and selecting the target mean intensity value from a plurality of target mean intensity values based on a relative number of pixels, in each captured digital image, that have an intensity value that falls outside a range of intensity values.