1. . 
The amount by which a log measurement must be adjusted to remove the contribution of the borehole. Although most log measurements are designed to pick up a minimum of signal from the borehole, some contribution usually remains. This contribution may be removed by software or by manual entry into correction charts. In resistivity logging, the correction replaces the borehole with a resistivity equal to that of the formation. In nuclear logging, the correction adjusts the reading to that which would be found in a standard condition, such as an 8-in [20-cm] borehole filled with fresh water.