diff --git a/rtengine/dcrop.cc b/rtengine/dcrop.cc
index 71030f35b..513039ad6 100644
--- a/rtengine/dcrop.cc
+++ b/rtengine/dcrop.cc
@@ -696,37 +696,48 @@ void Crop::update (int todo)
         int fw = skips(parent->fw, skip);
         int fh = skips(parent->fh, skip);
         bool need_cropping = false;
+        bool need_fattal = true;
 
         if (trafx || trafy || trafw != fw || trafh != fh) {
             need_cropping = true;
             // fattal needs to work on the full image. So here we get the full
             // image from imgsrc, and replace the denoised crop in case
-            f = new Imagefloat(fw, fh);
-            fattalCrop.reset(f);
-            PreviewProps pp (0, 0, parent->fw, parent->fh, skip);
-            int tr = getCoarseBitMask(params.coarse);
-            parent->imgsrc->getImage(parent->currWB, tr, f, pp, params.toneCurve, params.icm, params.raw);
-            parent->imgsrc->convertColorSpace(f, params.icm, parent->currWB);
+            if (!params.dirpyrDenoise.enabled && skip == 1 && parent->fattal_11_dcrop_cache) {
+                f = parent->fattal_11_dcrop_cache;
+                need_fattal = false;
+            } else {
+                f = new Imagefloat(fw, fh);
+                fattalCrop.reset(f);
+                PreviewProps pp (0, 0, parent->fw, parent->fh, skip);
+                int tr = getCoarseBitMask(params.coarse);
+                parent->imgsrc->getImage(parent->currWB, tr, f, pp, params.toneCurve, params.icm, params.raw);
+                parent->imgsrc->convertColorSpace(f, params.icm, parent->currWB);
 
-            if (params.dirpyrDenoise.enabled) {
-                // copy the denoised crop
-                int oy = trafy / skip;
-                int ox = trafx / skip;
+                if (params.dirpyrDenoise.enabled) {
+                    // copy the denoised crop
+                    int oy = trafy / skip;
+                    int ox = trafx / skip;
 #ifdef _OPENMP
-                #pragma omp parallel for
+                    #pragma omp parallel for
 #endif
-                for (int y = 0; y < baseCrop->getHeight(); ++y) {
-                    int dy = oy + y;
-                    for (int x = 0; x < baseCrop->getWidth(); ++x) {
-                        int dx = ox + x;
-                        f->r(dy, dx) = baseCrop->r(y, x);
-                        f->g(dy, dx) = baseCrop->g(y, x);
-                        f->b(dy, dx) = baseCrop->b(y, x);
+                    for (int y = 0; y < baseCrop->getHeight(); ++y) {
+                        int dy = oy + y;
+                        for (int x = 0; x < baseCrop->getWidth(); ++x) {
+                            int dx = ox + x;
+                            f->r(dy, dx) = baseCrop->r(y, x);
+                            f->g(dy, dx) = baseCrop->g(y, x);
+                            f->b(dy, dx) = baseCrop->b(y, x);
+                        }
                     }
+                } else if (skip == 1) {
+                    parent->fattal_11_dcrop_cache = f; // cache this globally
+                    fattalCrop.release();
                 }
             }
         }
-        parent->ipf.ToneMapFattal02(f);
+        if (need_fattal) {
+            parent->ipf.ToneMapFattal02(f);
+        }
 
         // crop back to the size expected by the rest of the pipeline
         if (need_cropping) {
@@ -735,7 +746,7 @@ void Crop::update (int todo)
             int oy = trafy / skip;
             int ox = trafx / skip;
 #ifdef _OPENMP
-#pragma omp parallel for
+            #pragma omp parallel for
 #endif
             for (int y = 0; y < trafh; ++y) {
                 int cy = y + oy;
diff --git a/rtengine/improccoordinator.cc b/rtengine/improccoordinator.cc
index 9172fbf96..532068eee 100644
--- a/rtengine/improccoordinator.cc
+++ b/rtengine/improccoordinator.cc
@@ -33,7 +33,7 @@ namespace rtengine
 extern const Settings* settings;
 
 ImProcCoordinator::ImProcCoordinator ()
-    : orig_prev (nullptr), oprevi (nullptr), oprevl (nullptr), nprevl (nullptr), previmg (nullptr), workimg (nullptr),
+    : orig_prev (nullptr), oprevi (nullptr), oprevl (nullptr), nprevl (nullptr), fattal_11_dcrop_cache(nullptr), previmg (nullptr), workimg (nullptr),
       ncie (nullptr), imgsrc (nullptr), shmap (nullptr), lastAwbEqual (0.), lastAwbTempBias (0.0), ipf (&params, true), monitorIntent (RI_RELATIVE),
       softProof (false), gamutCheck (false), scale (10), highDetailPreprocessComputed (false), highDetailRawComputed (false),
       allocated (false), bwAutoR (-9000.f), bwAutoG (-9000.f), bwAutoB (-9000.f), CAMMean (NAN),
@@ -111,6 +111,10 @@ ImProcCoordinator::~ImProcCoordinator ()
     mProcessing.lock();
     mProcessing.unlock();
     freeAll ();
+    if (fattal_11_dcrop_cache) {
+        delete fattal_11_dcrop_cache;
+        fattal_11_dcrop_cache = nullptr;
+    }
 
     std::vector<Crop*> toDel = crops;
 
@@ -386,6 +390,10 @@ void ImProcCoordinator::updatePreviewImage (int todo, Crop* cropCall)
     readyphase++;
 
     if ((todo & M_HDR) && params.fattal.enabled) {
+        if (fattal_11_dcrop_cache) {
+            delete fattal_11_dcrop_cache;
+            fattal_11_dcrop_cache = nullptr;
+        }
         ipf.ToneMapFattal02(orig_prev);
         if (oprevi != orig_prev) {
             delete oprevi;
diff --git a/rtengine/improccoordinator.h b/rtengine/improccoordinator.h
index 41b901e93..2f5fe52e5 100644
--- a/rtengine/improccoordinator.h
+++ b/rtengine/improccoordinator.h
@@ -57,6 +57,7 @@ protected:
     Imagefloat *oprevi;
     LabImage *oprevl;
     LabImage *nprevl;
+    Imagefloat *fattal_11_dcrop_cache; // global cache for ToneMapFattal02 used in 1:1 detail windows (except when denoise is active)
     Image8 *previmg;  // displayed image in monitor color space, showing the output profile as well (soft-proofing enabled, which then correspond to workimg) or not
     Image8 *workimg;  // internal image in output color space for analysis
     CieImage *ncie;