Fix Paganin documentation, use one convention

nabu/preproc/phase.py

@@ -29,8 +29,6 @@ def lmicron_to_db(Lmicron, energy, distance):
     .. math::
        L^2 = \\pi \\lambda D \\frac{\\delta}{\\beta}
 
-    The PyHST2 normalization differs from the one used by other softwares
-    like tomopy by a factor :math:`1/(4\pi^2)`
     """
     L2 = Lmicron**2
     wavelength = 1.23984199e-3 / energy
@@ -144,7 +142,7 @@ class PaganinPhaseRetrieval(object):
         The radio is divided, in the Fourier domain, by the original "Paganin filter" `[1]`.
         .. math::
 
-          F = 1 + \\frac{\\delta}{\\beta} \\lambda D \\rho |k|^2
+          F = 1 + \\frac{\\delta}{\\beta} \\lambda D \\pi |k|^2
 
         where k is the wave vector, computed as
 
@@ -154,8 +152,6 @@ class PaganinPhaseRetrieval(object):
 
         where P is the pixel size, N the number of pixels in one direction,
         and :math:`l \\in [0, N-1]`.
-        The factor :math:`\\rho` is either :math:`\\pi` or :math:`1/(4\\pi^2)`
-        depending on the convention (default is the former).
 
 
         References
@@ -275,8 +271,7 @@ class PaganinPhaseRetrieval(object):
         D = self.distance_micron
         L = self.wavelength_micron
         db = self.delta_beta
-        self.paganin_filter = 1.0 / (1 + db * L * D * pi * k2)  # HST / savu
-        #~ self.paganin_filter = 1.0 / (1 + db * L * D * k2/ (4*pi))  # Paganin / tomopy
+        self.paganin_filter = 1.0 / (1 + db * L * D * pi * k2)
 
     def pad_with_values(self, data, top_val=0, bottom_val=0, left_val=0,
                         right_val=0):