Time-lapse seismic is now a core technology for reservoir monitoring and characterization. However, many challenges continue to exist in its application in complex geology (e.g. sub-salt reservoirs). Differences in acquisition geometry (non-repeatability) and poor illumination are examples of factors that cause contamination of the desired time-lapse effects (i.e. changes due to production). By computing the time-lapse response as a difference between least-squares inverse images or posing time-lapse imaging as a least-squares inverse problem, we hope to attenuate geometry and other unwanted effects.