Abstract: The invention relates to an estimate of the seismic illumination fold (x,p) in the migrated 3D domain at an image point x, for a dip of vector p characterized in that the illumination fold I (z, p; s, r) is estimated for each (source s, receiver r) pair in the seismic survey, by applying the following steps:—determination of the reflection travel time tr (·xr (p); s·r) from the source s to the specular reflection point z, on the plane reflector passing through the image point x and perpendicular to the dip vector p, and then return to the reflector r; starting from the diffraction travel time td (·z;s·r) from the source to the said image point x and then return to the reflector r;—incrementing the said illumination fold I (X, p;s, r) related to the said (source s, receiver r) pair as a function of the difference between the diffraction travel time td (x; s, r) and the reflection travel time tr(xr (p)isrr).