1. A method for digital radiographic 3D volume image reconstruction of a subject, executed at least in part on a computer, comprising: obtaining image data at a first binning mode for a plurality of 2D projection images over a range of scan angles; generating, for each of the plurality of 2D projection images, an increased-spatial resolution projection image by: (i) providing an image representation of a different corresponding object at a second higher spatial resolution binning mode; (ii) determining an image data transformation for the first binning mode according to the image representation obtained at the second higher spatial resolution binning mode; (iii) applying the image data transformation individually to the plurality of 2D projection images obtained at the first binning mode to generate the increased-spatial resolution plurality of 2D projection images; and storing the increased-spatial resolution plurality of 2D projection images in a computer-accessible memory.