In this video BEST IPC master instructor Tammy Grefkowitz discusses the various magnification requirements of IPC-A-610 when inspecting PCBs. Tammy discusses when you should use what magnification as well as what the "refereeing" guidelines stipulate.
More on IPC-A-610 training here:
http://www.ipctraining.com/ipc-a-610-inspection-pcbs/
