diff --git a/rtengine/iplocallab.cc b/rtengine/iplocallab.cc
index e11fdf50c..6b2c7ae47 100644
--- a/rtengine/iplocallab.cc
+++ b/rtengine/iplocallab.cc
@@ -2447,7 +2447,7 @@ static void showmask(const local_params& lp, int xstart, int ystart, int cx, int
     }
 }
 
-void maskcalccol(int bfw, int bfh, int xstart, int ystart, int sk, int cx, int cy, LabImage* bufcolorig, LabImage* bufmaskblurcol, LabImage* originalmaskcol, LabImage* original, /*LabImage * transformed, */int inv, const struct local_params & lp,
+void maskcalccol(bool invmask, int bfw, int bfh, int xstart, int ystart, int sk, int cx, int cy, LabImage* bufcolorig, LabImage* bufmaskblurcol, LabImage* originalmaskcol, LabImage* original, /*LabImage * transformed, */int inv, const struct local_params & lp,
                  const LocCCmaskCurve & locccmasCurve, bool & lcmasutili, const  LocLLmaskCurve & locllmasCurve, bool & llmasutili, const  LocHHmaskCurve & lochhmasCurve, bool &lhmasutili, bool multiThread,
                  bool enaMask, bool showmaske, bool deltaE, bool modmask, bool zero, bool modif, float chrom, float rad, float gamma, float slope, float blendm)
 {
@@ -2456,7 +2456,9 @@ void maskcalccol(int bfw, int bfh, int xstart, int ystart, int sk, int cx, int c
     float meanfab, fab;
     mean_fab(xstart, ystart, bfw, bfh, bufcolorig, original, fab, meanfab, chrom);
 //    meanfab = 5000.f;
-
+    float kinv = 1.f;
+    float kneg = 1.f;
+    if(invmask) {kinv = 0.f; kneg = -1.f;}
     if (deltaE || modmask || enaMask || showmaske) {
 
 #ifdef _OPENMP
@@ -2506,11 +2508,11 @@ void maskcalccol(int bfw, int bfh, int xstart, int ystart, int sk, int cx, int c
                     float kmaskH = 0.f;
 
                     if (locllmasCurve && llmasutili) {
-                        kmaskL = 32768.f * LIM01(1.f - locllmasCurve[(500.f / 32768.f) * bufcolorig->L[ir][jr]]);
+                        kmaskL = 32768.f * LIM01(kinv - kneg * locllmasCurve[(500.f / 32768.f) * bufcolorig->L[ir][jr]]);
                     }
 
                     if (!deltaE && locccmasCurve && lcmasutili) {
-                        kmaskC = LIM01(1.f - locccmasCurve[500.f * (0.0001f + sqrt(SQR(bufcolorig->a[ir][jr]) + SQR(bufcolorig->b[ir][jr])) / fab)]);
+                        kmaskC = LIM01(kinv  - kneg * locccmasCurve[500.f * (0.0001f + sqrt(SQR(bufcolorig->a[ir][jr]) + SQR(bufcolorig->b[ir][jr])) / fab)]);
                     }
 
                     if (lochhmasCurve && lhmasutili) {
@@ -2526,7 +2528,7 @@ void maskcalccol(int bfw, int bfh, int xstart, int ystart, int sk, int cx, int c
                             h -= 1.f;
                         }
 
-                        const float valHH = LIM01(1.f - lochhmasCurve[500.f *  h]);
+                        const float valHH = LIM01(kinv - kneg * lochhmasCurve[500.f *  h]);
 
                         if (!deltaE) {
                             kmaskH = valHH;
@@ -7275,7 +7277,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
                     float gamma = lp.gammacb;
                     float slope = lp.slomacb;
                     float blendm = lp.blendmacb;
-                    maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, loctemp.get(), bufmaskorigcb.get(), originalmaskcb.get(), original, inv, lp,
+                    maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, loctemp.get(), bufmaskorigcb.get(), originalmaskcb.get(), original, inv, lp,
                                 locccmascbCurve, lcmascbutili, locllmascbCurve, llmascbutili, lochhmascbCurve, lhmascbutili, multiThread,
                                 enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -7544,7 +7546,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
                     float blendm = lp.blendmatm;
 
                     if (!params->locallab.spots.at(sp).enatmMaskaft) {
-                        maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, bufgbm.get(), bufmaskorigtm.get(), originalmasktm.get(), original, inv, lp,
+                        maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, bufgbm.get(), bufmaskorigtm.get(), originalmasktm.get(), original, inv, lp,
                                     locccmastmCurve, lcmastmutili, locllmastmCurve, llmastmutili, lochhmastmCurve, lhmastmutili, multiThread,
                                     enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -7566,7 +7568,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
 
                         if (enatmMasktmap) {
                             //calculate new values for original, originalmasktm, bufmaskorigtm...in function of tmp1
-                            maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, tmp1.get(), bufmaskorigtm.get(), originalmasktm.get(), original, inv, lp,
+                            maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, tmp1.get(), bufmaskorigtm.get(), originalmasktm.get(), original, inv, lp,
                                         locccmastmCurve, lcmastmutili, locllmastmCurve, llmastmutili, lochhmastmCurve, lhmastmutili, multiThread,
                                         enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -7721,7 +7723,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
                     float gamma = lp.gammaSH;
                     float slope = lp.slomaSH;
                     float blendm = lp.blendmaSH;
-                    maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, bufexporig.get(), bufmaskorigSH.get(), originalmaskSH.get(), original, inv, lp,
+                    maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, bufexporig.get(), bufmaskorigSH.get(), originalmaskSH.get(), original, inv, lp,
                                 locccmasSHCurve, lcmasSHutili, locllmasSHCurve, llmasSHutili, lochhmasSHCurve, lhmasSHutili, multiThread,
                                 enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -7814,7 +7816,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
             float slope = lp.slomaSH;
             float blendm = lp.blendmaSH;
 
-            maskcalccol(GW, GH, 0, 0, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskSH.get(), original, inv, lp,
+            maskcalccol(false, GW, GH, 0, 0, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskSH.get(), original, inv, lp,
                         locccmasSHCurve, lcmasSHutili, locllmasSHCurve, llmasSHutili, lochhmasSHCurve, lhmasSHutili, multiThread,
                         enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -9889,8 +9891,8 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
                     float gamma = lp.gammaexp;
                     float slope = lp.slomaexp;
                     float blendm = lp.blendmaexp;
-
-                    maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, bufexporig.get(), bufmaskblurexp.get(), originalmaskexp.get(), original, inv, lp,
+                   // bool invmask = params->locallab.spots.at(sp).enaExpMaskaft;
+                    maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, bufexporig.get(), bufmaskblurexp.get(), originalmaskexp.get(), original, inv, lp,
                                 locccmasexpCurve, lcmasexputili, locllmasexpCurve, llmasexputili, lochhmasexpCurve, lhmasexputili, multiThread,
                                 enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -10152,8 +10154,9 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
             float gamma = lp.gammaexp;
             float slope = lp.slomaexp;
             float blendm = lp.blendmaexp;
+           // bool invmask = params->locallab.spots.at(sp).enaExpMaskaft;
 
-            maskcalccol(GW, GH, 0, 0, sk, cx, cy, bufexporig.get(), bufmaskblurexp.get(), originalmaskexp.get(), original, inv, lp,
+            maskcalccol(false, GW, GH, 0, 0, sk, cx, cy, bufexporig.get(), bufmaskblurexp.get(), originalmaskexp.get(), original, inv, lp,
                         locccmasexpCurve, lcmasexputili, locllmasexpCurve, llmasexputili, lochhmasexpCurve, lhmasexputili, multiThread,
                         enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -10390,7 +10393,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
                     float gamma = lp.gammacol;
                     float slope = lp.slomacol;
                     float blendm = lp.blendmacol;
-                    maskcalccol(bfw, bfh, xstart, ystart, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskcol.get(), original, inv, lp,
+                    maskcalccol(false, bfw, bfh, xstart, ystart, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskcol.get(), original, inv, lp,
                                 locccmasCurve, lcmasutili, locllmasCurve, llmasutili, lochhmasCurve, lhmasutili, multiThread,
                                 enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
@@ -10591,7 +10594,7 @@ void ImProcFunctions::Lab_Local(int call, int sp, float** shbuffer, LabImage * o
             float slope = lp.slomacol;
             float blendm = lp.blendmacol;
 
-            maskcalccol(GW, GH, 0, 0, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskcol.get(), original, inv, lp,
+            maskcalccol(false, GW, GH, 0, 0, sk, cx, cy, bufcolorig.get(), bufmaskblurcol.get(), originalmaskcol.get(), original, inv, lp,
                         locccmasCurve, lcmasutili, locllmasCurve, llmasutili, lochhmasCurve, lhmasutili, multiThread,
                         enaMask, showmaske, deltaE, modmask, zero, modif, chrom, rad, gamma, slope, blendm);
 
diff --git a/rtgui/locallab.cc b/rtgui/locallab.cc
index 1b83d3ec7..9fdca4b82 100644
--- a/rtgui/locallab.cc
+++ b/rtgui/locallab.cc
@@ -5013,7 +5013,7 @@ void Locallab::inversexChanged()
         exnoiseMethod->hide();
         showmaskexpMethod->hide();
         showmaskexpMethodinv->show();
-
+        expMethod->set_active(0);
         if (expMethod->get_active_row_number() == 0) {
             pdeFrame->hide();
             fatFrame->hide();
@@ -8215,6 +8215,7 @@ void Locallab::updateSpecificGUIState()
         showmaskexpMethod->hide();
         softradiusexp->show();
 
+        expMethod->set_active(0);
         if (expMethod->get_active_row_number() == 0) {
             pdeFrame->hide();
             fatFrame->hide();