diff --git a/rtengine/curves.cc b/rtengine/curves.cc
index 361062d81..d76626cb8 100644
--- a/rtengine/curves.cc
+++ b/rtengine/curves.cc
@@ -592,7 +592,6 @@ void CurveFactory::curveToningLL ( bool & llctoningutili,const std::vector<doubl
 									 LUTu & outBeforeCCurveHistogram,
 									 ToneCurve & customToneCurve1,
 									 ToneCurve & customToneCurve2,
-									 
 									 int skip) {
 		
 		
@@ -675,37 +674,12 @@ void CurveFactory::curveToningLL ( bool & llctoningutili,const std::vector<doubl
 				hlCurve[i]=exp_scale;
 			float scalemshoulder = scale - shoulder;
 
-			// SSE makes more sense than omp here
-#ifdef __SSE2__
-			int i;
-			__m128 exp_scalev = _mm_set1_ps(exp_scale);
-			__m128 scalemshoulderv = _mm_set1_ps(scalemshoulder);
-			__m128 compv = _mm_set1_ps(comp);
-			__m128 valv = _mm_set_ps(4.f,3.f,2.f,1.f);
-			__m128 onev = _mm_set1_ps(1.f);
-			__m128 fourv = _mm_set1_ps(4.f);
-			for (i=shoulder+1; i<0xFFFD; i+=4) {
-				// change to [0,1] range
-				__m128 Rv = valv*compv/(scalemshoulderv);
-				_mm_storeu_ps(&hlCurve[i],xlogf(onev+Rv*exp_scalev)/Rv);
-				valv += fourv;
-			}
-			for (; i<0x10000; i++) {
-				// change to [0,1] range
-				float val = (float)i-shoulder;
-				float R = val*comp/(scalemshoulder);
-				hlCurve[i] = xlogf(1.f+R*exp_scale)/R;
-			}
-
-#else
 			for (int i=shoulder+1; i<0x10000; i++) {
 				// change to [0,1] range
 				float val = (float)i-shoulder;
 				float R = val*comp/(scalemshoulder);
-				hlCurve[i] = xlogf(1.f+R*exp_scale)/R;
+				hlCurve[i] = xlog(1.0+R*exp_scale)/R; // don't use xlogf or 1.f here. Leads to errors caused by too low precision
 			}
-#endif
-
 		}
 
 
diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index 4ee5b9dfe..82a2dcef0 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -36,7 +36,7 @@ ImProcCoordinator::ImProcCoordinator ()
       bwAutoR(-9000.f), bwAutoG(-9000.f), bwAutoB(-9000.f), CAMMean(0.), chaut(0.f), redaut(0.f), blueaut(0.f), maxredaut(0.f), maxblueaut(0.f),nresi(0.f),
 		chromina(0.f), sigma(0.f), lumema(0.f),minredaut(0.f), minblueaut(0.f),
 
-      hltonecurve(65536,0),
+      hltonecurve(65536,LUT_CLIP_BELOW),  // used LUT_CLIP_BELOW, because we want to have a baseline of 2^expcomp in this curve. If we don't clip the lut we get wrong values, see Issue 2621 #14 for details
       shtonecurve(65536,2),//clip above
       tonecurve(65536,0),//,1);
 
diff --git a/rtengine/simpleprocess.cc b/rtengine/simpleprocess.cc
index fefcdafee..53276bd3e 100644
--- a/rtengine/simpleprocess.cc
+++ b/rtengine/simpleprocess.cc
@@ -589,7 +589,7 @@ IImage16* processImage (ProcessingJob* pjob, int& errorCode, ProgressListener* p
     }
     // RGB processing
 
-    LUTf curve1 (65536,0);
+    LUTf curve1 (65536,LUT_CLIP_BELOW); // used LUT_CLIP_BELOW, because we want to have a baseline of 2^expcomp in this curve. If we don't clip the lut we get wrong values, see Issue 2621 #14 for details
     LUTf curve2 (65536,0);
 	LUTf curve (65536,0);
 	LUTf satcurve (65536,0);