diff --git a/src/components/Viewfinder.tsx b/src/components/Viewfinder.tsx
index 3b7c6e5..e0d5b24 100644
--- a/src/components/Viewfinder.tsx
+++ b/src/components/Viewfinder.tsx
@@ -20,6 +20,7 @@ import {
   ColorMatrix,
   Image as SkiaImage,
   ImageShader,
+  BlendMode,
   TileMode,
   FilterMode,
   MipmapMode,
@@ -353,11 +354,18 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
     // eslint-disable-next-line react-hooks/exhaustive-deps
     []
   );
+  // Highlight Diffusion Filter strength (0..10); 0 = no glow pass.
+  const hdfSync = useMemo(
+    () => createSynchronizable<number>(adjustments.hdf ?? 0),
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+    []
+  );
   useEffect(() => {
     colorMatrixSync.setBlocking(colorMatrix);
     toneSync.setBlocking(toneParams);
     cinemaSync.setBlocking(cinemaParams ? cinemaParams.flat : cinemaOffFlat());
-  }, [colorMatrix, toneParams, cinemaParams, colorMatrixSync, toneSync, cinemaSync]);
+    hdfSync.setBlocking(adjustments.hdf ?? 0);
+  }, [colorMatrix, toneParams, cinemaParams, adjustments.hdf, colorMatrixSync, toneSync, cinemaSync, hdfSync]);
 
   // Camera controller lives behind SkiaCamera. AE bias is not tracked live:
   // flushExposureBias() below applies it right before each photo capture so the
@@ -714,10 +722,12 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
         // one frame. Validate + try/catch, fall back to identity (no filter):
         // a 1-frame gain error beats a 1-frame black beat. DEBUG-EV.
         const paint = Skia.Paint();
+        let baseColorFilter: ReturnType<typeof Skia.ColorFilter.MakeMatrix> | null = null;
         try {
           const cm = colorMatrixSync.getDirty();
           if (cm != null && cm.length === 20 && cm.every((v) => typeof v === 'number' && Number.isFinite(v))) {
-            paint.setColorFilter(Skia.ColorFilter.MakeMatrix(cm));
+            baseColorFilter = Skia.ColorFilter.MakeMatrix(cm);
+            paint.setColorFilter(baseColorFilter);
           } else {
             console.warn('Invalid color matrix (len ' + (cm == null ? 'null' : cm.length) + ') — filter skipped');
           }
@@ -733,6 +743,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
         // ignores the paint shader, which is why the DR/Highlight/Shadow tone
         // never showed on the live preview) or as a plain color-matrix image.
         const drawFullFrame = () => {
+          let fullShader = null;
           if (hasTone || hasCinema) {
             try {
               const imageShader = frameTexture.makeShaderOptions(T_CLAMP, T_CLAMP, F_LINEAR, M_NONE);
@@ -744,13 +755,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
                 const cinemaShader = cinemaEffect.makeShaderWithChildren(cinema, [final ?? imageShader]);
                 if (cinemaShader != null) final = cinemaShader;
               }
-              if (final != null) {
-                const w = frameTexture.width();
-                const h = frameTexture.height();
-                paint.setShader(final);
-                canvas.drawRect(Skia.XYWHRect(0, 0, w, h), paint);
-                return;
-              }
+              if (final != null) fullShader = final;
             } catch (e) {
               if (!toneFailLogged.getBlocking()) {
                 toneFailLogged.setBlocking(true);
@@ -758,7 +763,55 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
               }
             }
           }
-          canvas.drawImage(frameTexture, 0, 0, paint);
+          if (fullShader != null) {
+            const w = frameTexture.width();
+            const h = frameTexture.height();
+            paint.setShader(fullShader);
+            canvas.drawRect(Skia.XYWHRect(0, 0, w, h), paint);
+          } else {
+            canvas.drawImage(frameTexture, 0, 0, paint);
+          }
+          // HDF: mirror of export pass 5b — extract highlights with a hard
+          // contrast curve, blur that selection, Screen it back on top. Screen
+          // against near-black is a no-op, so shadows stay put. Same source
+          // (shader or image) the base draw used, so the glow sits on processed
+          // pixels. Radius is a fraction of width so preview/export bloom alike.
+          const hdfV = hdfSync.getDirty();
+          if (hdfV > 0) {
+            const strength = hdfV / 10;
+            const width = frameTexture.width();
+            const sigma = width * (0.004 + 0.015 * strength);
+            const hiMatrix = [
+              2.5, 0, 0, 0, -1.5,
+              0, 2.5, 0, 0, -1.5,
+              0, 0, 2.5, 0, -1.5,
+              0, 0, 0, 1, 0,
+            ];
+            const hiFilter = Skia.ColorFilter.MakeMatrix(hiMatrix);
+            // Order is load-bearing (see exportEngine pass 5b): chain both as
+            // image filters so the highlight selection runs BEFORE the blur.
+            const selection = Skia.ImageFilter.MakeColorFilter(
+              baseColorFilter != null
+                ? Skia.ColorFilter.MakeCompose(hiFilter, baseColorFilter)
+                : hiFilter,
+              null
+            );
+            const glowPaint = Skia.Paint();
+            glowPaint.setBlendMode(BlendMode.Screen);
+            glowPaint.setAlphaf(0.15 + 0.35 * strength);
+            glowPaint.setImageFilter(
+              Skia.ImageFilter.MakeCompose(
+                Skia.ImageFilter.MakeBlur(sigma, sigma, TileMode.Clamp, null),
+                selection
+              )
+            );
+            if (fullShader != null) {
+              glowPaint.setShader(fullShader);
+              canvas.drawRect(Skia.XYWHRect(0, 0, width, frameTexture.height()), glowPaint);
+            } else {
+              canvas.drawImage(frameTexture, 0, 0, glowPaint);
+            }
+          }
         };
         // Composition band: without this the SkiaCamera layer later cover-fits
         // the upright snapshot onto the fullscreen view, so a 4:3 ratio band
@@ -857,7 +910,7 @@ const Viewfinder = forwardRef<ViewfinderHandle, ViewfinderProps>(function Viewfi
       });
       frame.dispose();
     },
-    [colorMatrixSync, toneSync, cinemaSync, toneFailLogged, feedRectSync, frameBeatSync]
+    [colorMatrixSync, toneSync, cinemaSync, hdfSync, toneFailLogged, feedRectSync, frameBeatSync]
   );
 
   const grainOpacity = adjustments.grain / 20;