(1) The difference observed between two different well-logging measurements of the same or related parameters recorded or plotted on the same [[log]] (e.g., porosities, [[formation factor log|formation factor curves]], etc.)

(2) The differences observed between two similar well logging measurements, made at different [[depth of investigation|depths of investigation]], recorded or plotted on the same log (e.g., [[resistivity|resistivities]], [[movable oil plot]], etc.).