1. A method comprising: receiving first seismic data acquired by one or more receivers in response to energy produced by one or more seismic sources interacting with a subsurface feature, wherein: the first seismic data being indicative of measured reflection coefficients for image points for the subsurface feature, the measured reflection coefficients being associated with incidence angles, and a range of the incidence angles varying with respect to an image point position; and processing the first seismic data in a machine to generate second data indicative of a normal incidence reflection coefficient for at least one of the image points not associated with a normal angle of incidence.