diff --git a/rtengine/curves.h b/rtengine/curves.h
index 27cd9366c..bb2daab5b 100644
--- a/rtengine/curves.h
+++ b/rtengine/curves.h
@@ -61,8 +61,8 @@ class CurveFactory {
             return 0.0;
         double k = sqrt ((m1-1.0)*(m1-m2)/2) / (1.0-m2);
         double l = (m1-m2) / (1.0-m2) + k;
-        double lx = log(x);
-        return m2*x + (1.0-m2)*(2.0 - exp(k*lx))*exp(l*lx);
+        double lx = xlog(x);
+        return m2*x + (1.0-m2)*(2.0 - xexp(k*lx))*xexp(l*lx);
     }
     // basic concave function between (0,0) and (1,1). m1 and m2 controls the slope at the start and end point
     static inline double baseu (double x, double m1, double m2) {
@@ -220,6 +220,12 @@ class Curve {
     int ppn;			// targeted polyline point number
     double* x;
     double* y;
+    // begin of variables used in Parametric curves only
+    double mc;
+    double mfc;
+    double msc;
+    double mhc;
+    // end of variables used in Parametric curves only
     std::vector<double> poly_x;		// X points of the faceted curve
     std::vector<double> poly_y;		// Y points of the faceted curve
     std::vector<HashEntry> hash;
diff --git a/rtengine/diagonalcurves.cc b/rtengine/diagonalcurves.cc
index 545759b4e..fe816b736 100644
--- a/rtengine/diagonalcurves.cc
+++ b/rtengine/diagonalcurves.cc
@@ -80,6 +80,11 @@ DiagonalCurve::DiagonalCurve (const std::vector<double>& p, int poly_pn) {
                     x[8] = 1.0;
                 else
                     x[8] = p[8]/100.0;
+				mc = -xlog(2.0)/xlog(x[2]);
+				double mbase = pfull (0.5, x[8], x[6], x[5]);
+				mfc = mbase<=1e-14 ? 0.0 : xexp(xlog(mbase)/mc);			// value of the curve at the center point
+				msc = -xlog(2.0)/xlog(x[1]/x[2]);
+				mhc = -xlog(2.0)/xlog((x[3]-x[2])/(1-x[2]));
             }
         }
         if (identity) {
@@ -221,28 +226,21 @@ double DiagonalCurve::getVal (double t) const {
     case DCT_Parametric : {
         if (t<=1e-14)
             return 0.0;
-        double c = -log(2.0)/log(x[2]);
-        double tv = exp(c*log(t));
+        double tv = xexp(mc*xlog(t));
         double base = pfull (tv, x[8], x[6], x[5]);
-        double stretched = base<=1e-14 ? 0.0 : exp(log(base)/c);
+        double stretched = base<=1e-14 ? 0.0 : xexp(xlog(base)/mc);
 
-        base = pfull (0.5, x[8], x[6], x[5]);
-        double fc = base<=1e-14 ? 0.0 : exp(log(base)/c);   // value of the curve at the center point
         if (t<x[2]) {
             // add shadows effect:
-            double sc = -log(2.0)/log(x[1]/x[2]);
-            double stv = exp(sc*log(stretched/fc));
+            double stv = xexp(msc*xlog(stretched/mfc));
             double sbase = pfull (stv, x[8], x[7], 0.5);
-            double sstretched = fc*(sbase<=1e-14 ? 0.0 : exp(log(sbase)/sc));
-            return sstretched;
+            return mfc*(sbase<=1e-14 ? 0.0 : xexp(xlog(sbase)/msc));
         }
         else {
             // add highlights effect:
-            double hc = -log(2.0)/log((x[3]-x[2])/(1-x[2]));
-            double htv = exp(hc*log((stretched-fc)/(1-fc)));
+            double htv = xexp(mhc*xlog((stretched-mfc)/(1-mfc)));
             double hbase = pfull (htv, x[8], 0.5, x[4]);
-            double hstretched = fc + (1-fc)*(hbase<=1e-14 ? 0.0 : exp(log(hbase)/hc));
-            return hstretched;
+            return mfc + (1-mfc)*(hbase<=1e-14 ? 0.0 : xexp(xlog(hbase)/mhc));
         }
         break;
     }
diff --git a/rtengine/ipvibrance.cc b/rtengine/ipvibrance.cc
index 51c14e68d..4c51ad374 100644
--- a/rtengine/ipvibrance.cc
+++ b/rtengine/ipvibrance.cc
@@ -44,43 +44,27 @@ using namespace procparams;
 
 extern const Settings* settings;
 
-void fillCurveArrayVib(DiagonalCurve* diagCurve, LUTf &outCurve, int skip, bool needed) {
-	if (needed && diagCurve) {
-		LUTf lutCurve (65536);
+void fillCurveArrayVib(DiagonalCurve* diagCurve, LUTf &outCurve, bool needed) {
 
-		for (int i=0; i<=0xffff; i+= i<0xffff-skip ? skip : 1 ) {
+	if (needed && diagCurve) {
+#ifdef _OPENMP
+#pragma omp parallel for
+#endif
+		for (int i=0; i<=0xffff; i++ ) {
 			// change to [0,1] range
 			// apply custom/parametric/NURBS curve, if any
 			// and store result in a temporary array
-			lutCurve[i] = diagCurve->getVal( double(i)/65535.0 );
-		}
-
-		// if skip>1, let apply linear interpolation in the skipped points of the curve
-		if (skip > 1) {
-			int prev = 0;
-			for (int i=1; i<=0xffff-skip; i++) {
-				int iMod = i%skip;
-				if (!iMod) {
-					prev+=skip;
-					continue;
-				}
-				lutCurve[i] = ( lutCurve[prev] * (skip-iMod) + lutCurve[prev+skip]*iMod ) / skip;
-			}
-		}
-
-		for (int i=0; i<=0xffff; i++) {
-			outCurve[i] = (65535.0f * lutCurve[i]);
-		}
+			outCurve[i] = 65535.f*diagCurve->getVal( double(i)/65535.0 );
+		}
 	}
 	else {
 		for (int i=0; i<=0xffff; i++) {
 			outCurve[i] = float(i);
 		}
-	}
+	}
 }
 
 
-
 /*
  * Vibrance correction
  * copyright (c)2011  Jacques Desmis <jdesmis@gmail.com> and Jean-Christophe Frisch <natureh@free.fr>
@@ -88,10 +72,12 @@ void fillCurveArrayVib(DiagonalCurve* diagCurve, LUTf &outCurve, int skip, bool
  */
 void ImProcFunctions::vibrance (LabImage* lab) {
 
-	int skip=1; //scale==1 ? 1 : 16;
+	if (!params->vibrance.enabled)
+		return;
+//	int skip=1; //scale==1 ? 1 : 16;
 	bool skinCurveIsSet=false;
 	DiagonalCurve* dcurve = NULL;
-	dcurve = new DiagonalCurve (params->vibrance.skintonescurve, CURVES_MIN_POLY_POINTS/skip);
+	dcurve = new DiagonalCurve (params->vibrance.skintonescurve, CURVES_MIN_POLY_POINTS);
 	if (dcurve) {
 		if (!dcurve->isIdentity()) {
 			skinCurveIsSet = true;
@@ -102,11 +88,11 @@ void ImProcFunctions::vibrance (LabImage* lab) {
 		}
 	}
 
-	if (!params->vibrance.enabled || (!skinCurveIsSet && !params->vibrance.pastels && !params->vibrance.saturated)) {
+	if (!skinCurveIsSet && !params->vibrance.pastels && !params->vibrance.saturated) {
 		if (dcurve) {
 			delete dcurve;
 			dcurve = NULL;
-		}
+		}
 		return;
 	}
 
@@ -121,8 +107,8 @@ void ImProcFunctions::vibrance (LabImage* lab) {
 	// skin hue curve
 	// I use diagonal because I think it's better
 	LUTf skin_curve (65536,0);
-
-	fillCurveArrayVib(dcurve, skin_curve, skip, skinCurveIsSet);
+	if(skinCurveIsSet)
+		fillCurveArrayVib(dcurve, skin_curve, skinCurveIsSet);
 	if (dcurve) {
 		delete dcurve;
 		dcurve = NULL;