def KS93(shear1, shear2):
'''KS-inversion from shear to convergence, using Schneider eq 44.
Requires cython code KSI.pyx'''
smap = shear1 + shear2 * 1.0j
smap = smap
smap = smap.astype(complex128)
D = D_kernel(31)
D = D.astype(complex128)
kmap = KSI.KSI_calc(smap, D)
return real(kmap)
