diff --git a/rtengine/filmnegativeproc.cc b/rtengine/filmnegativeproc.cc
index 64f7a697b..948e86957 100644
--- a/rtengine/filmnegativeproc.cc
+++ b/rtengine/filmnegativeproc.cc
@@ -104,8 +104,8 @@ bool RawImageSource::getFilmNegativeExponents (Coord2D spotA, Coord2D spotB, int
       std::swap(clearVals, denseVals);
 
     if (settings->verbose) {
-        printf("Clear film values:  R=%f G=%f B=%f\n", clearVals[0], clearVals[1], clearVals[2]);
-        printf("Dense film values:  R=%f G=%f B=%f\n", denseVals[0], denseVals[1], denseVals[2]);
+        printf("Clear film values:  R=%g G=%g B=%g\n", clearVals[0], clearVals[1], clearVals[2]);
+        printf("Dense film values:  R=%g G=%g B=%g\n", denseVals[0], denseVals[1], denseVals[2]);
     }
 
     float denseGreenRatio = clearVals[1] / denseVals[1];
@@ -119,7 +119,7 @@ bool RawImageSource::getFilmNegativeExponents (Coord2D spotA, Coord2D spotB, int
             newExps[ch] = CLAMP(logBase(clearVals[ch] / denseVals[ch], denseGreenRatio), 0.3f, 3.f);
 
     if (settings->verbose)
-        printf("New exponents:  R=%f G=%f B=%f\n", newExps[0], newExps[1], newExps[2]);
+        printf("New exponents:  R=%g G=%g B=%g\n", newExps[0], newExps[1], newExps[2]);
 
     return true;
 }
@@ -230,20 +230,23 @@ void RawImageSource::filmNegativeProcess(const procparams::FilmNegativeParams &p
     float mults[3] = { 1.f };  // Channel normalization multipliers
 
     for (int c=0; c<3; c++) {
-        // Find median values for each channel using a histogram search function
-        findMinMaxPercentile(&cvs[c][0], cvs[c].size(), 0.5f, medians[c], 0.5f, medians[c], true);
-        // Determine the channel multipler so that N times the median becomes 65k. This clips away
-        // the values in the dark border surrounding the negative (due to the film holder, for example),
-        // the reciprocal of which have blown up to stellar values.
-        mults[c] = MAX_OUT_VALUE / (medians[c] * 24);
+        // Find median values for each channel
+        if(cvs[c].size() > 0) {
+            std::sort(cvs[c].begin(), cvs[c].end());
+            medians[c] = cvs[c].at(cvs[c].size() / 2);
+            // Determine the channel multipler so that N times the median becomes 65k. This clips away
+            // the values in the dark border surrounding the negative (due to the film holder, for example),
+            // the reciprocal of which have blown up to stellar values.
+            mults[c] = MAX_OUT_VALUE / (medians[c] * 24);
+        }
     }
 
 
     t4.set();
     if (settings->verbose) {
         printf("Sample count : %lu, %lu, %lu\n", cvs[0].size(), cvs[1].size(), cvs[2].size());
-        printf("Medians : %f %f %f\n", medians[0], medians[1], medians[2] );
-        printf("Computed multipliers : %f %f %f\n", mults[0], mults[1], mults[2] );
+        printf("Medians : %g %g %g\n", medians[0], medians[1], medians[2] );
+        printf("Computed multipliers : %g %g %g\n", mults[0], mults[1], mults[2] );
         printf("Median calc time us: %d\n", t4.etime(t3));
     }
 
diff --git a/rtgui/filmnegative.cc b/rtgui/filmnegative.cc
index bf4c22837..94c6db4dd 100644
--- a/rtgui/filmnegative.cc
+++ b/rtgui/filmnegative.cc
@@ -34,7 +34,7 @@ FilmNegative::FilmNegative () : FoldableToolPanel(this, "filmnegative", M("TP_FI
 {
 
     auto mkExponentAdjuster = [this](Glib::ustring label, double defaultVal) {
-        Adjuster *adj = Gtk::manage(new Adjuster (label, 0.3, 3, 0.01, defaultVal)); //exponent
+        Adjuster *adj = Gtk::manage(new Adjuster (label, 0.3, 5, 0.001, defaultVal)); //exponent
         adj->setAdjusterListener (this);
     
         if (adj->delay < options.adjusterMaxDelay) {
@@ -49,6 +49,9 @@ FilmNegative::FilmNegative () : FoldableToolPanel(this, "filmnegative", M("TP_FI
     greenExp = mkExponentAdjuster(M("TP_FILMNEGATIVE_GREEN"), 1.0);
     blueExp  = mkExponentAdjuster(M("TP_FILMNEGATIVE_BLUE"), 0.86);
 
+    redRatio = redExp->getValue() / greenExp->getValue();
+    blueRatio = blueExp->getValue() / greenExp->getValue();
+
     auto m = ProcEventMapper::getInstance();
     EvFilmNegativeEnabled = m->newEvent(ALL, "HISTORY_MSG_FILMNEGATIVE_ENABLED");
     EvFilmNegativeExponents = m->newEvent(ALL, "HISTORY_MSG_FILMNEGATIVE_EXPONENTS");
@@ -139,10 +142,23 @@ void FilmNegative::enabledChanged()
 
 void FilmNegative::adjusterChanged(Adjuster* a, double newval)
 {
-    if (listener && getEnabled()) {
+    if (listener) {
         if(a == redExp || a == greenExp || a == blueExp) {
-            listener->panelChanged (EvFilmNegativeExponents, Glib::ustring::compose (
-                "R=%1 ; G=%2 ; B=%3", redExp->getTextValue(), greenExp->getTextValue(), blueExp->getTextValue()));
+            disableListener();
+            if(a == greenExp) {
+                redExp->setValue(a->getValue() * redRatio);
+                blueExp->setValue(a->getValue() * blueRatio);
+            } else if(a == redExp) {
+                redRatio = newval / greenExp->getValue();
+            } else if(a == blueExp) {
+                blueRatio = newval / greenExp->getValue();
+            }
+            enableListener();
+            
+            if(getEnabled()) {
+                listener->panelChanged (EvFilmNegativeExponents, Glib::ustring::compose (
+                    "R=%1 ; G=%2 ; B=%3", redExp->getTextValue(), greenExp->getTextValue(), blueExp->getTextValue()));
+            }
         }
     }
 }
diff --git a/rtgui/filmnegative.h b/rtgui/filmnegative.h
index 614e60fb5..5d6c8ce03 100644
--- a/rtgui/filmnegative.h
+++ b/rtgui/filmnegative.h
@@ -54,6 +54,8 @@ private:
     Gtk::ToggleButton* spotbutton;
     sigc::connection spotConn;
 
+    double redRatio, blueRatio;
+
     void editToggled ();
 
 public: