Radiographic imaging using the (a) 5× and (b) 10× microscope objectives on an extremely round metal sphere embedded in epoxy and evaluation of its diameter. The `bubbles' visible in the images (particularly with 10× magnification) are air pockets in the epoxy tube. The red line in both images indicates the line profile used in the software Fiji (Schindelin et al., 2012). Selected profile data points were used to fit linear functions, and the intercepts of the two functions at each end were adopted as the edges of the sphere. The distance between these two end points was calculated to obtain the sphere diameter for both 5× and 10× magnification, as indicated.