The Abrams-Lind formulation of degenerate four-wave phase conjugation is generalized to treat signal-pump detuning. The theory is an extension of two-wave grating-dip spectroscopy. We find that the reflection passband of phase conjugation is limited by the power-broadened bandwidth of the population difference, a width that can be very narrow. Unlike the running-wave saturator case, the signal absorption saturated by a standing wave shows no gain. This is due to the presence of appreciable amounts of unsaturated medium between spatial holes. We also generalize the degenerate three-wave mixing coefficients of Heer to include signal-pump detuning.