The very limited depth of field of a microscope necessitates doing depth stacking for every field of view. This is done automatically by the apparatus. As a side effect, it gives a heightmap, but with the lens used for the whole-painting scan (what HIROX calls "35x", corresponding to ~5 µm sampling resolution), the elevations are not reliable, especially near the edge of the field. For selected areas, a higher magnification was used that gives much more reliable elevations. Sadly, only a small fraction of the painting was imaged using this higher resolution, so the 3D data is spotty.
