1. An arrangement for adjusting at least one reading parameter of an imaging reader for reading targets by image capture over a range of working distances, the arrangement comprising: an energizable aiming assembly for directing an aiming light spot along an aiming axis to the target when energized; a controller for energizing and deenergizing the aiming assembly; an imaging assembly for capturing a first image of the target containing the aiming light spot with the aiming assembly energized, and for capturing a second image of the target without the aiming light spot with the aiming assembly deenergized, each image being captured in a frame over a field of view having an imaging axis offset from the aiming axis; an image pre-processor for comparing first image data from the first image with second image data from the second image over a common fractional region of both frames to obtain a position of the aiming light spot in the first image, and for determining a distance to the target based on the position of the aiming light spot in the first image; and the controller being further operative for adjusting the at least one reading parameter of the imaging reader based on the determined target distance.