diff --git a/rtdata/languages/default b/rtdata/languages/default
index 1ac0e40aa..8d0248fd9 100644
--- a/rtdata/languages/default
+++ b/rtdata/languages/default
@@ -1263,6 +1263,7 @@ TP_ICM_WORKINGPROFILE;Working Profile
 TP_IMPULSEDENOISE_LABEL;Impulse Noise Reduction
 TP_IMPULSEDENOISE_THRESH;Threshold
 TP_LABCURVE_AVOIDCOLORSHIFT;Avoid color shift
+TP_LABCURVE_CHROMA_TOOLTIP;To apply Bwtoning, set Chromaticity to -100
 TP_LABCURVE_AVOIDCOLORSHIFT_TOOLTIP;Fit colors into gamut of the working color space and apply Munsell correction
 TP_LABCURVE_BRIGHTNESS;Lightness
 TP_LABCURVE_CHROMATICITY;Chromaticity
diff --git a/rtengine/improcfun.cc b/rtengine/improcfun.cc
index 8bea8519e..638b12b0b 100644
--- a/rtengine/improcfun.cc
+++ b/rtengine/improcfun.cc
@@ -2965,6 +2965,7 @@ void ImProcFunctions::chromiLuminanceCurve (int pW, LabImage* lold, LabImage* ln
 	bool highlight = params->hlrecovery.enabled; //Get the value if "highlight reconstruction" is activated
 	int chromaticity = params->labCurve.chromaticity;
 	bool bwToning = params->labCurve.chromaticity==-100  /*|| params->blackwhite.method=="Ch" */ || params->blackwhite.enabled;
+	//if(chromaticity==-100) chromaticity==-99;
 	//if(bwToning) printf("OK bwto\n"); else printf("pas de bw\n");
 	bool LCredsk = params->labCurve.lcredsk;
 	bool ccut = ccutili;
@@ -3340,13 +3341,16 @@ void ImProcFunctions::chromiLuminanceCurve (int pW, LabImage* lold, LabImage* ln
 			else {
 //				if(Lprov1 > maxlp) maxlp=Lprov1;
 //				if(Lprov1 < minlp) minlp=Lprov1;
+				if(!bwToning){
 				lnew->L[i][j]=Lprov1*327.68f;
 				lnew->a[i][j]=327.68f*Chprov1*cos(HH);
 				lnew->b[i][j]=327.68f*Chprov1*sin(HH);
-
+				}
+				else {
 				//Luv limiter only
-				//lnew->a[i][j] = atmp;
-				//lnew->b[i][j] = btmp;
+				lnew->a[i][j] = atmp;
+				lnew->b[i][j] = btmp;
+				}
 			}
 		}
 } // end of parallelization
diff --git a/rtgui/labcurve.cc b/rtgui/labcurve.cc
index 4d96ef310..3fd6e2f51 100644
--- a/rtgui/labcurve.cc
+++ b/rtgui/labcurve.cc
@@ -32,6 +32,7 @@ LCurve::LCurve () : Gtk::VBox(), FoldableToolPanel(this) {
 	brightness = Gtk::manage (new Adjuster (M("TP_LABCURVE_BRIGHTNESS"), -100., 100., 1., 0.));
 	contrast   = Gtk::manage (new Adjuster (M("TP_LABCURVE_CONTRAST"), -100., 100., 1., 0.));
 	chromaticity   = Gtk::manage (new Adjuster (M("TP_LABCURVE_CHROMATICITY"), -100., 100., 1., 0.));
+	chromaticity->set_tooltip_markup(M("TP_LABCURVE_CHROMA_TOOLTIP"));
 
 	pack_start (*brightness);
 	brightness->show ();