diff --git a/Surface_mesher/changes.txt b/Surface_mesher/changes.txt
index 6e0aa6e905a..1ff526a104c 100644
--- a/Surface_mesher/changes.txt
+++ b/Surface_mesher/changes.txt
@@ -8,6 +8,8 @@
   Surface_mesher::refine_mesh. It is now template parameters of the class
   Surface_mesher. I have verified that the optimizer of GNU/CC is able to
   strip the debug code when NO_DEBUG is use.
+- change sligthly the code of examples, and modify sligthly the user manual
+  accordingly
 
 21 March 2006 Laurent Rineau
 - fix examples/Surface_mesher/3d_image_surface_mesher.C (stupid bug: the
diff --git a/Surface_mesher/doc_tex/Surface_mesher/main.tex b/Surface_mesher/doc_tex/Surface_mesher/main.tex
index dd4212a8be1..087eaa10e28 100644
--- a/Surface_mesher/doc_tex/Surface_mesher/main.tex
+++ b/Surface_mesher/doc_tex/Surface_mesher/main.tex
@@ -202,11 +202,15 @@ the automatically generated traits class
 In this example the surface to be meshed is defined
 as the locus of points with a given gray level
 in a 3D image.
-The code is quite similar to the previous example,
-except for the definition of the function
-which is passed to the creator of the surface.
-In this case, it is an instance of
-the \ccc{CGAL::Gray_level_image_3} class.
+The code is quite similar to the previous example. The parameters of the
+surface creator are different:
+\begin{itemize}
+\item the function is an instance of the \ccc{CGAL::Gray_level_image_3}
+  class, 
+\item the bounding sphere is chosen carefully, so that its center is inside
+  the surface and the radius high enough to actually bound the definition
+  domain of the 3D image.
+\end{itemize}
 \ccIncludeExampleCode{Surface_mesher/3d_image_surface_mesher.C}
 
 
diff --git a/Surface_mesher/examples/Surface_mesher/3d_image_surface_mesher.C b/Surface_mesher/examples/Surface_mesher/3d_image_surface_mesher.C
index dae8bbbc173..d8f4df9709f 100644
--- a/Surface_mesher/examples/Surface_mesher/3d_image_surface_mesher.C
+++ b/Surface_mesher/examples/Surface_mesher/3d_image_surface_mesher.C
@@ -10,8 +10,6 @@ typedef CGAL::Surface_mesh_cell_base_3<Kernel> Cb;
 typedef CGAL::Triangulation_data_structure_3<Vb, Cb> Tds;
 typedef CGAL::Delaunay_triangulation_3<Kernel, Tds> Tr;
 typedef CGAL::Surface_mesh_complex_2_in_triangulation_3<Tr> C2t3;
-typedef Kernel::Sphere_3 Sphere_3;
-typedef Kernel::Point_3 Point_3;
 
 typedef CGAL::Gray_level_image_3<Kernel::FT> Gray_level_image;
 typedef CGAL::Implicit_surface_3<Kernel, Gray_level_image> Surface_3;
@@ -20,11 +18,20 @@ int main(int, char **) {
   Tr tr;            // 3D-Delaunay triangulation
   C2t3 c2t3 (tr);   // 2D-complex in 3D-Delaunay triangulation
 
-  // defining the surface
   Gray_level_image image("ImageIO/data/skull_2.9.inr.gz", 2.9);
-  Surface_3 surface(image, 
-                    Sphere_3(Point_3(250., 250., 250.), 300.*300.*2.),
-                    1e-02);
+
+  // bounding_sphere_center is a point inside the surface defined by image.
+  Kernel::Point_3 bounding_sphere_center(122., 102., 117.);
+
+  // bounding_sphere_squared_radius is chosen so that the sphere bounds the
+  // whole image
+  Kernel::FT bounding_sphere_squared_radius = 200.*200.*2.;
+
+  Kernel::Sphere_3 bounding_sphere(bounding_sphere_center,
+                                   bounding_sphere_squared_radius);
+
+  // definition of the surface
+  Surface_3 surface(image, bounding_sphere, 1e-2);
 
   // defining meshing criteria
   CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,
diff --git a/Surface_mesher/examples/Surface_mesher/implicit_surface_mesher.C b/Surface_mesher/examples/Surface_mesher/implicit_surface_mesher.C
index 67fc4da1700..7f7dacc3507 100644
--- a/Surface_mesher/examples/Surface_mesher/implicit_surface_mesher.C
+++ b/Surface_mesher/examples/Surface_mesher/implicit_surface_mesher.C
@@ -25,8 +25,7 @@ int main(int, char **) {
 
   // defining the surface
   Surface_3 surface(sphere_function,            // pointer to function
-                    Sphere_3(CGAL::ORIGIN, 2.), // bounding sphere
-                    1e-03);  // precision for intersections computations
+                    Sphere_3(CGAL::ORIGIN, 2.)); // bounding sphere
 
   // defining meshing criteria
   CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,  //angular bound