The transfer function of the imaging process in magnetic force microscopy is calculated theoretically using a reciprocal force based approach. The reciprocal force is that exerted on the sample by the tip, and according to Newton’s third law, is simply equal but opposite to the force exerted on the tip by the sample. The method allows the role of the tip in the imaging process to be represented in a particularly simple fashion, and the system transfer function is shown to depend on the Fourier transform of the field distribution produced by the microscope tip at the surface of that tip, an exponential spacing loss term reflecting the separation of the tip and the sample and finally a loss term dependent on the sample thickness. ©1996 American Institute of Physics.