diff --git a/rtengine/color.cc b/rtengine/color.cc
index c0d52a7d6..13d320cc5 100644
--- a/rtengine/color.cc
+++ b/rtengine/color.cc
@@ -1593,7 +1593,7 @@ void Color::calcGamma (double pwr, double ts, int mode, GammaValues &gamma)
     bnd[g[1] >= 1.] = 1.;
 
     if (g[1] && (g[1] - 1.) * (g[0] - 1.) <= 0.) {
-        for (i = 0; i < 48; i++) {
+        for (i = 0; i < 99; i++) {
             g[2] = (bnd[0] + bnd[1]) / 2.;
 
             if (g[0]) {
diff --git a/rtengine/color.h b/rtengine/color.h
index 5b863d735..edcc02cb4 100644
--- a/rtengine/color.h
+++ b/rtengine/color.h
@@ -1073,25 +1073,29 @@ public:
 
     /**
     * @brief sRGB gamma
-    * See also calcGamma above with the following values: pwr=2.4  ts=12.92  mode=0.003041  imax=0.055011
+    * See also calcGamma above with the following values: pwr=2.399  ts=12.92  mode=0.003041  imax=0.055
     * @param x red, green or blue channel's value [0 ; 1]
     * @return the gamma modified's value [0 ; 1]
     */
     static inline double gamma2     (double x)      //  g3                  1+g4
     {
-        return x <= 0.003041 ? x * 12.92 : 1.055011 * exp(log(x) / sRGBGammaCurve) - 0.055011;
+      //  return x <= 0.003041 ? x * 12.92 : 1.055 * exp(log(x) / 2.39990) - 0.055;//calculate with calcgamma
+        return x <= 0.0031308 ? x * 12.92 : 1.055 * exp(log(x) / sRGBGammaCurve) - 0.055;
+		//very small differences between the 2
     }
 
 
     /**
     * @brief Inverse sRGB gamma
-    * See also calcGamma above with the following values: pwr=2.4  ts=12.92  mode=0.003041  imax=0.055011
+    * See also calcGamma above with the following values: pwr=2.3999  ts=12.92  mode=0.003041  imax=0.055
     * @param x red, green or blue channel's value [0 ; 1]
     * @return the inverse gamma modified's value [0 ; 1]
     */
     static inline double igamma2    (double x)      //g2
     {
-        return x <= 0.039293 ? x / 12.92 : exp(log((x + 0.055011) / 1.055011) * sRGBGammaCurve);
+       // return x <= 0.039289 ? x / 12.92 : exp(log((x + 0.055) / 1.055) * 2.39990);//calculate with calcgamma
+        return x <= 0.04045 ? x / 12.92 : exp(log((x + 0.055) / 1.055) * sRGBGammaCurve);
+		//very small differences between the 2
     }
 
 
diff --git a/rtengine/iccstore.cc b/rtengine/iccstore.cc
index 50ff58878..15fb366a0 100644
--- a/rtengine/iccstore.cc
+++ b/rtengine/iccstore.cc
@@ -1083,7 +1083,7 @@ void rtengine::ICCStore::getGammaArray(const procparams::ColorManagementParams &
         ga[3] = 1. / slope;
         ga[5] = 0.0;
         ga[6] = 0.0;
-        //printf("ga[0]=%f ga[1]=%f ga[2]=%f ga[3]=%f ga[4]=%f\n", ga[0],ga[1],ga[2],ga[3],ga[4]);
+        printf("ga[0]=%f ga[1]=%f ga[2]=%f ga[3]=%f ga[4]=%f\n", ga[0],ga[1],ga[2],ga[3],ga[4]);
     }
 }
 
diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index 3edca9f45..be8aa2533 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -27,6 +27,7 @@
 #include <iostream>
 #include <fstream>
 #include <string>
+#include "color.h"
 
 #ifdef _OPENMP
 #include <omp.h>
@@ -316,6 +317,16 @@ void ImProcCoordinator::updatePreviewImage (int todo, Crop* cropCall)
             awbListener->WBChanged (params.wb.temperature, params.wb.green);
         }
 		
+/*		
+        GammaValues g_a;
+        double pwr = 1.0 / params.icm.gampos;
+        double ts = params.icm.slpos;
+
+
+        int mode = 0;
+        Color::calcGamma(pwr, ts, mode, g_a); // call to calcGamma with selected gamma and slope
+	        printf("ga[0]=%f ga[1]=%f ga[2]=%f ga[3]=%f ga[4]=%f\n", g_a[0],g_a[1],g_a[2],g_a[3],g_a[4]);
+	
             Glib::ustring datal;
 			datal = "lutsrgb.txt";
 		            ofstream fou(datal, ios::out | ios::trunc);
@@ -323,13 +334,13 @@ void ImProcCoordinator::updatePreviewImage (int todo, Crop* cropCall)
 		for(int i=0; i < 212; i++) {
 			//printf("igamma2=%i\n", (int) 65535.f*Color::igamma2(i/212.0));
 					float gam = Color::igamma2(i/211.0);
-					int lutga = 65535.f* gam;
+					int lutga = nearbyint(65535.f* gam);
                   //  fou << 65535*(int)Color::igamma2(i/212.0) << endl;
                     fou << i << " " << lutga << endl;
 			
 		}	
                 fou.close();
-		
+*/		
         int tr = getCoarseBitMask (params.coarse);
 
         imgsrc->getFullSize (fw, fh, tr);
diff --git a/rtengine/rawimagesource.cc b/rtengine/rawimagesource.cc
index a89cfc1bf..653c4294f 100644
--- a/rtengine/rawimagesource.cc
+++ b/rtengine/rawimagesource.cc
@@ -2103,7 +2103,7 @@ void RawImageSource::retinexPrepareBuffers(const ColorManagementParams& cmp, con
         int mode = 0;
         Color::calcGamma(pwr, ts, mode, g_a); // call to calcGamma with selected gamma and slope
 
-        //    printf("g_a0=%f g_a1=%f g_a2=%f g_a3=%f g_a4=%f\n", g_a0,g_a1,g_a2,g_a3,g_a4);
+   //        printf("g_a0=%f g_a1=%f g_a2=%f g_a3=%f g_a4=%f\n", g_a0,g_a1,g_a2,g_a3,g_a4);
         double start;
         double add;
 
diff --git a/rtgui/icmpanel.cc b/rtgui/icmpanel.cc
index f71ff354b..ce0c6a8f7 100644
--- a/rtgui/icmpanel.cc
+++ b/rtgui/icmpanel.cc
@@ -243,7 +243,7 @@ ICMPanel::ICMPanel () : FoldableToolPanel(this, "icm", M("TP_ICM_LABEL")), iunch
     freegamma->set_active (false);
     fgFrame->set_label_widget(*freegamma);
 
-    gampos = Gtk::manage(new Adjuster (M("TP_GAMMA_CURV"), 1, 3.5, 0.01, 2.22));
+    gampos = Gtk::manage(new Adjuster (M("TP_GAMMA_CURV"), 1, 3.5, 0.00001, 2.22));
     gampos->setAdjusterListener (this);
 
     if (gampos->delay < options.adjusterMaxDelay) {