diff --git a/rtengine/dcraw.patch b/rtengine/dcraw.patch
index e00393219..826580dff 100644
--- a/rtengine/dcraw.patch
+++ b/rtengine/dcraw.patch
@@ -661,29 +661,29 @@
 +                double d = tpp->defGain * image[i* ::width+j][1];
 +                if (d>64000)
 +                    continue;
-+                avg_g += d*d*d*d*d*d;
++                avg_g += d;
 +                gn++;
 +            }
 +            if (FISRED(filter,i,j)) {
 +                double d = tpp->defGain * image[i* ::width+j][0];
 +                if (d>64000)
 +                    continue;
-+                avg_r += d*d*d*d*d*d;
++                avg_r += d;
 +                rn++;
 +            }
 +            if (FISBLUE(filter,i,j)) {
 +                double d = tpp->defGain * image[i* ::width+j][2];
 +                if (d>64000)
 +                    continue;
-+                avg_b += d*d*d*d*d*d;
++                avg_b += d;
 +                bn++;
 +            }
 +        }
 +    }
 +
-+    double reds   = pow (avg_r/rn, 1.0/6.0) * tpp->camwbRed;
-+    double greens = pow (avg_g/gn, 1.0/6.0) * tpp->camwbGreen;
-+    double blues  = pow (avg_b/bn, 1.0/6.0) * tpp->camwbBlue;
++    double reds   = avg_r/rn * tpp->camwbRed;
++    double greens = avg_g/gn * tpp->camwbGreen;
++    double blues  = avg_b/bn * tpp->camwbBlue;
 +    
 +    double rm = rgb_cam[0][0]*reds + rgb_cam[0][1]*greens + rgb_cam[0][2]*blues;
 +    double gm = rgb_cam[1][0]*reds + rgb_cam[1][1]*greens + rgb_cam[1][2]*blues;
diff --git a/rtengine/rtthumbnail.cc b/rtengine/rtthumbnail.cc
index 7a7cff322..9e88698cf 100644
--- a/rtengine/rtthumbnail.cc
+++ b/rtengine/rtthumbnail.cc
@@ -116,18 +116,17 @@ Thumbnail* Thumbnail::loadFromImage (const Glib::ustring& fname, int &w, int &h,
     double avg_g = 0;
     double avg_b = 0;
     int n = 0;
-    int p = 6;
     for (int i=1; i<img->height-1; i++)
         for (int j=1; j<img->width-1; j++) {
             int ofs = 3*(i*img->width + j);
             if (img->data[ofs]>250 || img->data[ofs+1]>250 || img->data[ofs+2]>250)
                 continue;
-            avg_r += StdImageSource::intpow((double)img->data[ofs]*256, p);
-            avg_g += StdImageSource::intpow((double)img->data[ofs+1]*256, p);
-            avg_b += StdImageSource::intpow((double)img->data[ofs+2]*256, p);
+            avg_r += img->data[ofs];
+            avg_g += img->data[ofs+1];
+            avg_b += img->data[ofs+2];
             n++;
         }
-    ColorTemp::mul2temp (pow(avg_r/n, 1.0/p), pow(avg_g/n, 1.0/p), pow(avg_b/n, 1.0/p), tpp->autowbTemp, tpp->autowbGreen);
+    ColorTemp::mul2temp (avg_r/n, avg_g/n, avg_b/n, tpp->autowbTemp, tpp->autowbGreen);
 
     delete img;
     tpp->init ();