diff --git a/rtengine/ffmanager.cc b/rtengine/ffmanager.cc
index 82aa709b7..6b0302d1e 100644
--- a/rtengine/ffmanager.cc
+++ b/rtengine/ffmanager.cc
@@ -138,7 +138,7 @@ void ffInfo::updateRawImage()
             int H = ri->get_height();
             int W = ri->get_width();
             ri->compress_image(0);
-            int rSize = W * ((ri->getSensorType() == ST_BAYER || ri->getSensorType() == ST_FUJI_XTRANS) ? 1 : 3);
+            int rSize = W * ((ri->getSensorType() == ST_BAYER || ri->getSensorType() == ST_FUJI_XTRANS || ri->get_colors() == 1) ? 1 : 3);
             acc_t **acc = new acc_t*[H];
 
             for( int row = 0; row < H; row++) {
@@ -160,7 +160,7 @@ void ffInfo::updateRawImage()
                     temp->compress_image(0);     //\ TODO would be better working on original, because is temporary
                     nFiles++;
 
-                    if( ri->getSensorType() == ST_BAYER || ri->getSensorType() == ST_FUJI_XTRANS ) {
+                    if( ri->getSensorType() == ST_BAYER || ri->getSensorType() == ST_FUJI_XTRANS || ri->get_colors() == 1 ) {
                         for( int row = 0; row < H; row++) {
                             for( int col = 0; col < W; col++) {
                                 acc[row][col] += temp->data[row][col];
diff --git a/rtengine/imagesource.h b/rtengine/imagesource.h
index af9eecc35..c0565a4a3 100644
--- a/rtengine/imagesource.h
+++ b/rtengine/imagesource.h
@@ -87,6 +87,7 @@ public:
     // use right after demosaicing image, add coarse transformation and put the result in the provided Imagefloat*
     virtual void        getImage    (const ColorTemp &ctemp, int tran, Imagefloat* image, const PreviewProps &pp, const ToneCurveParams &hlp, const RAWParams &raw) = 0;
     virtual eSensorType getSensorType () const = 0;
+    virtual bool        isMono () const = 0;
     // true is ready to provide the AutoWB, i.e. when the image has been demosaiced for RawImageSource
     virtual bool        isWBProviderReady () = 0;
 
diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index ff1bd7b3a..e22aa3b0d 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -215,7 +215,7 @@ void ImProcCoordinator::updatePreviewImage (int todo, Crop* cropCall)
     // If high detail (=100%) is newly selected, do a demosaic update, since the last was just with FAST
 
     if (imageTypeListener) {
-        imageTypeListener->imageTypeChanged (imgsrc->isRAW(), imgsrc->getSensorType() == ST_BAYER, imgsrc->getSensorType() == ST_FUJI_XTRANS);
+        imageTypeListener->imageTypeChanged (imgsrc->isRAW(), imgsrc->getSensorType() == ST_BAYER, imgsrc->getSensorType() == ST_FUJI_XTRANS, imgsrc->isMono());
     }
 
     if (   (todo & M_RAW)
diff --git a/rtengine/rawimagesource.cc b/rtengine/rawimagesource.cc
index aef4447ce..5dd671ce9 100644
--- a/rtengine/rawimagesource.cc
+++ b/rtengine/rawimagesource.cc
@@ -2815,7 +2815,7 @@ void RawImageSource::processFlatField(const RAWParams &raw, RawImage *riFlatFile
         cfaboxblur(riFlatFile, cfablur, BS, BS);
     }
 
-    if(ri->getSensorType() == ST_BAYER) {
+    if(ri->getSensorType() == ST_BAYER || ri->get_colors() == 1) {
         float refcolor[2][2];
 
         //find centre average values by channel
@@ -2823,8 +2823,8 @@ void RawImageSource::processFlatField(const RAWParams &raw, RawImage *riFlatFile
             for (int n = 0; n < 2; n++) {
                 int row = 2 * (H >> 2) + m;
                 int col = 2 * (W >> 2) + n;
-                int c  = FC(row, col);
-                int c4 = ( c == 1 && !(row & 1) ) ? 3 : c;
+                int c  = ri->get_colors() != 1 ? FC(row, col) : 0;
+                int c4 = ri->get_colors() != 1 ? (( c == 1 && !(row & 1) ) ? 3 : c) : 0;
                 refcolor[m][n] = max(0.0f, cfablur[row * W + col] - black[c4]);
             }
 
@@ -2836,8 +2836,8 @@ void RawImageSource::processFlatField(const RAWParams &raw, RawImage *riFlatFile
             for (int m = 0; m < 2; m++)
                 for (int n = 0; n < 2; n++) {
                     float maxval = 0.f;
-                    int c  = FC(m, n);
-                    int c4 = ( c == 1 && !(m & 1) ) ? 3 : c;
+                    int c  = ri->get_colors() != 1 ? FC(m, n) : 0;
+                    int c4 = ri->get_colors() != 1 ? (( c == 1 && !(m & 1) ) ? 3 : c) : 0;
 #ifdef _OPENMP
                     #pragma omp parallel
 #endif
@@ -2886,13 +2886,20 @@ void RawImageSource::processFlatField(const RAWParams &raw, RawImage *riFlatFile
                 refcolor[m][n] *= limitFactor;
             }
 
+        unsigned int c[2][2] {};
+        unsigned int c4[2][2] {};
+        if(ri->get_colors() != 1) {
+            for (int i = 0; i < 2; ++i) {
+                for(int j = 0; j < 2; ++j) {
+                    c[i][j] = FC(i, j);
+                }
+            }
+            c4[0][0] = ( c[0][0] == 1) ? 3 : c[0][0];
+            c4[0][1] = ( c[0][1] == 1) ? 3 : c[0][1];
+            c4[1][0] = c[1][0];
+            c4[1][1] = c[1][1];
+        }
 
-        unsigned int c[2][2]  = {{FC(0, 0), FC(0, 1)}, {FC(1, 0), FC(1, 1)}};
-        unsigned int c4[2][2];
-        c4[0][0] = ( c[0][0] == 1) ? 3 : c[0][0];
-        c4[0][1] = ( c[0][1] == 1) ? 3 : c[0][1];
-        c4[1][0] = c[1][0];
-        c4[1][1] = c[1][1];
 
 #ifdef __SSE2__
         vfloat refcolorv[2] = {_mm_set_ps(refcolor[0][1], refcolor[0][0], refcolor[0][1], refcolor[0][0]),
@@ -3016,13 +3023,20 @@ void RawImageSource::processFlatField(const RAWParams &raw, RawImage *riFlatFile
         cfaboxblur(riFlatFile, cfablur1, 0, 2 * BS); //now do horizontal blur
         cfaboxblur(riFlatFile, cfablur2, 2 * BS, 0); //now do vertical blur
 
-        if(ri->getSensorType() == ST_BAYER) {
-            unsigned int c[2][2]  = {{FC(0, 0), FC(0, 1)}, {FC(1, 0), FC(1, 1)}};
-            unsigned int c4[2][2];
-            c4[0][0] = ( c[0][0] == 1) ? 3 : c[0][0];
-            c4[0][1] = ( c[0][1] == 1) ? 3 : c[0][1];
-            c4[1][0] = c[1][0];
-            c4[1][1] = c[1][1];
+        if(ri->getSensorType() == ST_BAYER || ri->get_colors() == 1) {
+            unsigned int c[2][2] {};
+            unsigned int c4[2][2] {};
+            if(ri->get_colors() != 1) {
+                for (int i = 0; i < 2; ++i) {
+                    for(int j = 0; j < 2; ++j) {
+                        c[i][j] = FC(i, j);
+                    }
+                }
+                c4[0][0] = ( c[0][0] == 1) ? 3 : c[0][0];
+                c4[0][1] = ( c[0][1] == 1) ? 3 : c[0][1];
+                c4[1][0] = c[1][0];
+                c4[1][1] = c[1][1];
+            }
 
 #ifdef __SSE2__
             vfloat blackv[2] = {_mm_set_ps(black[c4[0][1]], black[c4[0][0]], black[c4[0][1]], black[c4[0][0]]),
@@ -3140,6 +3154,9 @@ void RawImageSource::copyOriginalPixels(const RAWParams &raw, RawImage *src, Raw
                 }
             }
         }
+        if (riFlatFile && W == riFlatFile->get_width() && H == riFlatFile->get_height()) {
+            processFlatField(raw, riFlatFile, black);
+        }  // flatfield
     } else {
         // No bayer pattern
         // TODO: Is there a flat field correction possible?
diff --git a/rtengine/rawimagesource.h b/rtengine/rawimagesource.h
index ff7d2c1f9..78cfb86b8 100644
--- a/rtengine/rawimagesource.h
+++ b/rtengine/rawimagesource.h
@@ -145,6 +145,10 @@ public:
     {
         return ri != nullptr ? ri->getSensorType() : ST_NONE;
     }
+    bool        isMono () const
+    {
+        return ri->get_colors() == 1;
+    }
     ColorTemp   getWB       () const
     {
         return camera_wb;
diff --git a/rtengine/rtengine.h b/rtengine/rtengine.h
index 846366cee..687836c49 100644
--- a/rtengine/rtengine.h
+++ b/rtengine/rtengine.h
@@ -359,7 +359,7 @@ class ImageTypeListener
 {
 public :
     virtual ~ImageTypeListener() = default;
-    virtual void imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans) = 0;
+    virtual void imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans, bool is_Mono = false) = 0;
 };
 
 class WaveletListener
diff --git a/rtengine/stdimagesource.h b/rtengine/stdimagesource.h
index 304bc3d8d..62cca7d4f 100644
--- a/rtengine/stdimagesource.h
+++ b/rtengine/stdimagesource.h
@@ -52,6 +52,7 @@ public:
     ColorTemp   getSpotWB   (std::vector<Coord2D> &red, std::vector<Coord2D> &green, std::vector<Coord2D> &blue, int tran, double equal);
 
     eSensorType getSensorType() const {return ST_NONE;}
+    bool isMono() const {return false;}
 
     bool        isWBProviderReady ()
     {
diff --git a/rtgui/toolpanelcoord.cc b/rtgui/toolpanelcoord.cc
index a88feff7d..de8e28915 100644
--- a/rtgui/toolpanelcoord.cc
+++ b/rtgui/toolpanelcoord.cc
@@ -261,7 +261,7 @@ ToolPanelCoordinator::~ToolPanelCoordinator ()
     delete toolBar;
 }
 
-void ToolPanelCoordinator::imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans)
+void ToolPanelCoordinator::imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans, bool isMono)
 {
     if (isRaw) {
         if (isBayer) {
@@ -292,7 +292,20 @@ void ToolPanelCoordinator::imageTypeChanged (bool isRaw, bool isBayer, bool isXt
             };
             idle_register.add(func, this);
         }
-        else {
+        else if (isMono) {
+            const auto func = [](gpointer data) -> gboolean {
+                ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
+
+                self->rawPanelSW->set_sensitive (true);
+                self->sensorbayer->FoldableToolPanel::hide();
+                self->sensorxtrans->FoldableToolPanel::hide();
+                self->preprocess->FoldableToolPanel::hide();
+                self->flatfield->FoldableToolPanel::show();
+
+                return FALSE;
+            };
+            idle_register.add(func, this);
+        } else {
             const auto func = [](gpointer data) -> gboolean {
                 ToolPanelCoordinator* const self = static_cast<ToolPanelCoordinator*>(data);
 
diff --git a/rtgui/toolpanelcoord.h b/rtgui/toolpanelcoord.h
index b387ac988..5b9822ef2 100644
--- a/rtgui/toolpanelcoord.h
+++ b/rtgui/toolpanelcoord.h
@@ -218,7 +218,7 @@ public:
     // toolpanellistener interface
     void panelChanged   (rtengine::ProcEvent event, const Glib::ustring& descr);
 
-    void imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans);
+    void imageTypeChanged (bool isRaw, bool isBayer, bool isXtrans, bool isMono = false);
     // profilechangelistener interface
     void profileChange  (const rtengine::procparams::PartialProfile* nparams, rtengine::ProcEvent event, const Glib::ustring& descr, const ParamsEdited* paramsEdited = nullptr);
     void setDefaults    (rtengine::procparams::ProcParams* defparams);