Figure 3. MLEM reconstruction of Pawley scaling factors of titanium dioxide and barium sulfate from XRD data in the first column, along with their major elements, titanium and barium from XRF data in the second column, showing the presence of rutile in three paint layers and barite in two layers. Two trace elements, strontium and niobium, show less absorption because of their higher energetic emission lines. Sinogram dimensions are 1.2 mm(15-μm steps) by 180◦ (3◦ steps). Tomogram dimensions are 1.2 × 1.2mm (15 × 15 μmsteps).