  Recording and (computational) processing of complex wave fields offers a vast
realm of new optical methods. Also for optical 3D-metrology. We discuss
fundamental similarities and differences of holographic surface topography
measurement versus non-holographic principles, such as triangulation, classical
interferometry, rough surface interferometry and slope measuring methods. Key
features are the physical origin of the ultimate precision limit and how the
topographic information is encoded and decoded. We demonstrate that the
question "is holography just interferometry?" has different answers, depending
on how we exploit holograms or interferograms for metrology. The answers will
help users to find out if their measurement results could be improved or if
they already hit the ultimate limit of what physics allows.
