diff --git a/rtengine/diagonalcurves.cc b/rtengine/diagonalcurves.cc
index 23c1fba47..b2ac7414e 100644
--- a/rtengine/diagonalcurves.cc
+++ b/rtengine/diagonalcurves.cc
@@ -289,7 +289,8 @@ inline double catmull_rom_tj(double ti,
                              double xi, double yi,
                              double xj, double yj)
 {
-    return sqrt(sqrt(pow2(xj-xi) + pow2(yj-yi))) + ti;
+    static constexpr double alpha = 0.25;
+    return pow(sqrt(pow2(xj-xi) + pow2(yj-yi)), alpha) + ti;
 }
 
 
@@ -303,7 +304,7 @@ inline void catmull_rom_spline(int n_points,
 {
     res_x.reserve(n_points);
     res_y.reserve(n_points);
-    
+
     double t0 = 0;
     double t1 = catmull_rom_tj(t0, p0_x, p0_y, p1_x, p1_y);
     double t2 = catmull_rom_tj(t1, p1_x, p1_y, p2_x, p2_y);
@@ -359,15 +360,13 @@ void catmull_rom_chain(int n_points, int n_cp, double *x, double *y,
                        std::vector<double> &res_x, std::vector<double> &res_y)
 {
     static const double epsilon = 1e-5;
-    // double xr = x[1] - x[0];
-    // double yr = y[1] - y[0];
-    double xr = x[n_cp-1] - x[0];
-    double yr = y[n_cp-1] - y[0];
-    double x_first = x[0] - xr * 0.1;
+    double xr = x[1] - x[0];
+    double yr = y[1] - y[0];
+    double x_first = x[0] - xr * 0.01;
     double y_first = xr > epsilon ? (yr / xr) * (x_first - x[0]) + y[0] : y[0];
-    // xr = x[n_cp-1] - x[n_cp-2];
-    // yr = y[n_cp-1] - x[n_cp-2];
-    double x_last = x[n_cp-1] + xr * 0.1;
+    xr = x[n_cp-1] - x[n_cp-2];
+    yr = y[n_cp-1] - x[n_cp-2];
+    double x_last = x[n_cp-1] + xr * 0.01;
     double y_last = xr > epsilon ? (yr / xr) * (x_last - x[0]) + y[0] : y[0];
 
     int segments = n_cp - 1;
diff --git a/rtengine/histmatching.cc b/rtengine/histmatching.cc
index 184152ac8..d4f236d0e 100644
--- a/rtengine/histmatching.cc
+++ b/rtengine/histmatching.cc
@@ -221,20 +221,26 @@ void mappingToCurve(const std::vector<int> &mapping, std::vector<double> &curve)
         curve = { DCT_Linear }; // not enough points, fall back to linear
     } else {
         CubicSplineCurve c(curve);
-        curve.pop_back();
-        curve.pop_back();
-        double gap = coord(step);
-        while (1 - curve[curve.size()-2] > gap) {
-            double x = curve[curve.size()-2] + gap;
-            if (1 - x <= gap / 3) {
-                break;
-            }
+        double mid = coord(idx);
+        double x = 0.0;
+        constexpr double shgap = 0.075;
+        curve = { DCT_Spline };
+        while (mid - x > shgap / 2) {
             curve.push_back(x);
             curve.push_back(c.getVal(x));
+            x += shgap;
+        }
+        curve.push_back(mid);
+        curve.push_back(c.getVal(mid));
+        constexpr double hlgap = 0.2;
+        x = mid + hlgap;
+        while (1 - x > hlgap / 2) {
+            curve.push_back(x);
+            curve.push_back(c.getVal(x));
+            x += hlgap;
         }
         curve.push_back(1.0);
         curve.push_back(1.0);
-        curve.insert(curve.begin(), DCT_Spline);
     }
 }