Fast approximate focus operations providing an approximately focused image that is sufficiently focused to support certain subsequent inspection operations. The operations are particularly advantageous when used to provide images for successive inspection operations that predominate when inspecting planar workpieces. Improved inspection throughput is provided because, in contrast to conventional autofocus operations, the fast approximate focus operations do not acquire an image stack during a run mode as a basis for determining a best focused image. Rather, during learn mode, a representative feature-specific focus curve and a focus threshold value are determined and used during run mode to provide an approximately focused image that reliably supports certain inspection operations. In one embodiment, an acceptable approximately focused inspection image is provided within a limit of two focus adjustment moves that provide two corresponding images. The adjustment moves are based on the representative feature-specific focus curve provided in learn mode.