diff --git a/compose.yaml b/compose.yaml
index 8f5bab659..c158a7d1b 100644
--- a/compose.yaml
+++ b/compose.yaml
@@ -91,6 +91,7 @@ services:
       PHOTOPRISM_ASSETS_PATH: "/go/src/github.com/photoprism/photoprism/assets"
       PHOTOPRISM_STORAGE_PATH: "/go/src/github.com/photoprism/photoprism/storage"
       PHOTOPRISM_ORIGINALS_PATH: "/go/src/github.com/photoprism/photoprism/storage/originals"
+      PHOTOPRISM_ORIGINALS_LIMIT: 128000             # sets originals file size limit to 128 GB
       PHOTOPRISM_IMPORT_PATH: "/go/src/github.com/photoprism/photoprism/storage/import"
       PHOTOPRISM_DISABLE_CHOWN: "false"              # disables updating storage permissions via chmod and chown on startup
       PHOTOPRISM_DISABLE_BACKUPS: "false"            # disables backing up albums and photo metadata to YAML files
diff --git a/internal/config/config.go b/internal/config/config.go
index 370a275cb..975eb3939 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -62,6 +62,7 @@ import (
 
 // log points to the global logger.
 var log = event.Log
+var initThumbsMutex sync.Mutex
 
 // Config holds database, cache and all parameters of photoprism
 type Config struct {
@@ -86,11 +87,25 @@ func init() {
 		LowMem = TotalMem < MinMem
 	}
 
+	initThumbs()
+}
+
+func initThumbs() {
+	initThumbsMutex.Lock()
+	defer initThumbsMutex.Unlock()
+
+	maxSize := thumb.MaxSize()
+	Thumbs = ThumbSizes{}
+
 	// Init public thumb sizes for use in client apps.
 	for i := len(thumb.Names) - 1; i >= 0; i-- {
 		name := thumb.Names[i]
 		t := thumb.Sizes[name]
 
+		if t.Width > maxSize {
+			continue
+		}
+
 		if t.Public {
 			Thumbs = append(Thumbs, ThumbSize{Size: string(name), Usage: t.Usage, Width: t.Width, Height: t.Height})
 		}
@@ -254,6 +269,7 @@ func (c *Config) Propagate() {
 	thumb.SizeOnDemand = c.ThumbSizeUncached()
 	thumb.JpegQualityDefault = c.JpegQuality()
 	thumb.CachePublic = c.HttpCachePublic()
+	initThumbs()
 
 	// Set cache expiration defaults.
 	ttl.CacheDefault = c.HttpCacheMaxAge()
diff --git a/internal/config/extensions.go b/internal/config/extensions.go
index edee8b211..3ab3e26e2 100644
--- a/internal/config/extensions.go
+++ b/internal/config/extensions.go
@@ -17,16 +17,19 @@ var (
 // Register registers a new package extension.
 func Register(name string, initConfig func(c *Config) error, clientConfig func(c *Config, t ClientType) Map) {
 	extMutex.Lock()
+	defer extMutex.Unlock()
+
 	n, _ := extensions.Load().(Extensions)
 	extensions.Store(append(n, Extension{name: name, init: initConfig, clientValues: clientConfig}))
-	extMutex.Unlock()
 }
 
 // Ext returns all registered package extensions.
 func Ext() (ext Extensions) {
 	extMutex.Lock()
+	defer extMutex.Unlock()
+
 	ext, _ = extensions.Load().(Extensions)
-	extMutex.Unlock()
+
 	return ext
 }
 
diff --git a/internal/entity/search/viewer/result.go b/internal/entity/search/viewer/result.go
index abf79cb50..b2ff42111 100644
--- a/internal/entity/search/viewer/result.go
+++ b/internal/entity/search/viewer/result.go
@@ -23,7 +23,7 @@ type Result struct {
 	Hash         string        `json:"Hash"`
 	Codec        string        `json:"Codec,omitempty"`
 	Mime         string        `json:"Mime,omitempty"`
-	Thumbs       *thumb.Viewer `json:"Thumbs"`
+	Thumbs       *thumb.Viewer `json:"Thumbs,omitempty"`
 	DownloadUrl  string        `json:"DownloadUrl,omitempty"`
 }
 
diff --git a/internal/thumb/crop/image.go b/internal/thumb/crop/image.go
index fff80f210..c03c942db 100644
--- a/internal/thumb/crop/image.go
+++ b/internal/thumb/crop/image.go
@@ -23,6 +23,7 @@ var thumbFileNames = []string{
 	"%s_1920x1200_fit.jpg",
 	"%s_2560x1600_fit.jpg",
 	"%s_4096x4096_fit.jpg",
+	"%s_5120x5120_fit.jpg",
 	"%s_7680x4320_fit.jpg",
 }
 
@@ -33,6 +34,7 @@ var thumbFileSizes = []thumb.Size{
 	thumb.Sizes[thumb.Fit1920],
 	thumb.Sizes[thumb.Fit2560],
 	thumb.Sizes[thumb.Fit4096],
+	thumb.Sizes[thumb.Fit5120],
 	thumb.Sizes[thumb.Fit7680],
 }
 
@@ -56,10 +58,10 @@ func ImageFromThumb(thumbName string, area Area, size Size, cache bool) (img ima
 	// Cached?
 	if !fs.FileExists(cropName) {
 		// Do nothing.
-	} else if img, err := imaging.Open(cropName); err != nil {
+	} else if cropImg, cropErr := imaging.Open(cropName); cropErr != nil {
 		log.Errorf("crop: failed loading %s", filepath.Base(cropName))
 	} else {
-		return img, nil
+		return cropImg, nil
 	}
 
 	// Open thumb image file.
@@ -70,21 +72,21 @@ func ImageFromThumb(thumbName string, area Area, size Size, cache bool) (img ima
 	}
 
 	// Get absolute crop coordinates and dimension.
-	min, max, dim := area.Bounds(img)
+	posMin, posMax, dim := area.Bounds(img)
 
 	if dim < size.Width {
 		log.Debugf("crop: %s is too small, upscaling %dpx to %dpx", filepath.Base(thumbName), dim, size.Width)
 	}
 
 	// Crop area from image.
-	img = imaging.Crop(img, image.Rect(min.X, min.Y, max.X, max.Y))
+	img = imaging.Crop(img, image.Rect(posMin.X, posMin.Y, posMax.X, posMax.Y))
 
 	// Resample crop area.
 	img = thumb.Resample(img, size.Width, size.Height, size.Options...)
 
 	// Cache crop image?
 	if cache {
-		if err := imaging.Save(img, cropName); err != nil {
+		if err = imaging.Save(img, cropName); err != nil {
 			log.Errorf("crop: failed caching %s", filepath.Base(cropName))
 		} else {
 			log.Debugf("crop: saved %s", filepath.Base(cropName))
diff --git a/internal/thumb/fit.go b/internal/thumb/fit.go
index a45b01df8..e7320fcc9 100644
--- a/internal/thumb/fit.go
+++ b/internal/thumb/fit.go
@@ -6,6 +6,7 @@ import "image"
 // Best for the viewer as proportional resizing maintains the aspect ratio.
 var FitSizes = SizeList{
 	Sizes[Fit7680],
+	Sizes[Fit5120],
 	Sizes[Fit4096],
 	Sizes[Fit2560],
 	Sizes[Fit1920],
@@ -13,7 +14,7 @@ var FitSizes = SizeList{
 	Sizes[Fit720],
 }
 
-// Fit returns the largest fitting thumbnail size.
+// Fit returns the smallest fitting thumbnail size.
 func Fit(w, h int) (size Size) {
 	j := len(FitSizes) - 1
 
@@ -26,7 +27,7 @@ func Fit(w, h int) (size Size) {
 	return FitSizes[0]
 }
 
-// FitBounds returns the largest thumbnail size fitting the rectangle.
+// FitBounds returns the smallest thumbnail size fitting the rectangle.
 func FitBounds(r image.Rectangle) (s Size) {
 	return Fit(r.Dx(), r.Dy())
 }
diff --git a/internal/thumb/fit_test.go b/internal/thumb/fit_test.go
index 9612b0362..f6d86dcac 100644
--- a/internal/thumb/fit_test.go
+++ b/internal/thumb/fit_test.go
@@ -17,7 +17,9 @@ func TestFit(t *testing.T) {
 	assert.Equal(t, Sizes[Fit2560], Fit(1600, 1600))
 	assert.Equal(t, Sizes[Fit4096], Fit(1000, 3000))
 	assert.Equal(t, Sizes[Fit4096], Fit(2300, 2000))
-	assert.Equal(t, Sizes[Fit7680], Fit(5000, 5000))
+	assert.Equal(t, Sizes[Fit5120], Fit(5000, 2000))
+	assert.Equal(t, Sizes[Fit7680], Fit(6020, 2000))
+	assert.Equal(t, Sizes[Fit7680], Fit(8000, 8000))
 }
 
 func TestFitBounds(t *testing.T) {
diff --git a/internal/thumb/names.go b/internal/thumb/names.go
index 832e819f6..265b09e5e 100644
--- a/internal/thumb/names.go
+++ b/internal/thumb/names.go
@@ -33,12 +33,14 @@ const (
 	Fit2560  Name = "fit_2560"
 	Fit3840  Name = "fit_3840"
 	Fit4096  Name = "fit_4096"
+	Fit5120  Name = "fit_5120"
 	Fit7680  Name = "fit_7680"
 )
 
 // Names contains all default size names.
 var Names = []Name{
 	Fit7680,
+	Fit5120,
 	Fit4096,
 	Fit2560,
 	Fit1920,
diff --git a/internal/thumb/size_test.go b/internal/thumb/size_test.go
index 657a01105..262b9a77c 100644
--- a/internal/thumb/size_test.go
+++ b/internal/thumb/size_test.go
@@ -98,6 +98,19 @@ func TestSize_Skip(t *testing.T) {
 			t.Fatal(err)
 		}
 
+		assert.True(t, size.Skip(img))
+	})
+	t.Run("Fit5120", func(t *testing.T) {
+		size := Sizes[Fit5120]
+
+		assert.FileExists(t, src)
+
+		img, err := imaging.Open(src, imaging.AutoOrientation(true))
+
+		if err != nil {
+			t.Fatal(err)
+		}
+
 		assert.True(t, size.Skip(img))
 	})
 }
diff --git a/internal/thumb/sizes.go b/internal/thumb/sizes.go
index a846028b8..be5acfdfa 100644
--- a/internal/thumb/sizes.go
+++ b/internal/thumb/sizes.go
@@ -1,8 +1,9 @@
 package thumb
 
+// Default thumbnail size limits (cached and uncached).
 var (
 	SizeCached   = SizeFit1920.Width
-	SizeOnDemand = SizeFit7680.Width
+	SizeOnDemand = SizeFit5120.Width
 )
 
 // MaxSize returns the max supported size in pixels.
@@ -50,9 +51,10 @@ var (
 	SizeFit1600  = Size{Fit1600, Fit1920, "Social Media", 1600, 900, false, true, true, false, Options{ResampleFit, ResampleDefault}}
 	SizeFit1920  = Size{Fit1920, "", "Full HD", 1920, 1200, true, true, false, false, Options{ResampleFit, ResampleDefault}}
 	SizeFit2048  = Size{Fit2048, Fit4096, "DCI 2K, Tablets", 2048, 2048, false, true, true, false, Options{ResampleFit, ResampleDefault}}
-	SizeFit2560  = Size{Fit2560, Fit4096, "Quad HD, Notebooks", 2560, 1600, true, true, false, false, Options{ResampleFit, ResampleDefault}}
+	SizeFit2560  = Size{Fit2560, Fit4096, "Quad HD", 2560, 1600, true, true, false, false, Options{ResampleFit, ResampleDefault}}
 	SizeFit3840  = Size{Fit3840, Fit4096, "4K Ultra HD", 3840, 2400, false, true, true, false, Options{ResampleFit, ResampleDefault}}
 	SizeFit4096  = Size{Fit4096, "", "DCI 4K, Retina 4K", 4096, 4096, true, true, false, false, Options{ResampleFit, ResampleDefault}}
+	SizeFit5120  = Size{Fit5120, "", "Retina 5K", 5120, 5120, true, true, false, false, Options{ResampleFit, ResampleDefault}}
 	SizeFit7680  = Size{Fit7680, "", "8K Ultra HD 2", 7680, 4320, true, true, false, false, Options{ResampleFit, ResampleDefault}}
 )
 
@@ -74,5 +76,6 @@ var Sizes = SizeMap{
 	Fit2560:  SizeFit2560,
 	Fit3840:  SizeFit3840, // Deprecated in favor of Fit4096
 	Fit4096:  SizeFit4096,
+	Fit5120:  SizeFit5120,
 	Fit7680:  SizeFit7680,
 }
diff --git a/internal/thumb/thumb.go b/internal/thumb/thumb.go
index 258e226de..79fa9b19d 100644
--- a/internal/thumb/thumb.go
+++ b/internal/thumb/thumb.go
@@ -53,10 +53,10 @@ type Thumb struct {
 }
 
 // New creates a new photo thumbnail.
-func New(w, h int, hash string, s Size, contentUri, previewToken string) Thumb {
+func New(w, h int, hash string, s Size, contentUri, previewToken string) *Thumb {
 	if s.Width >= w && s.Height >= h {
 		// Smaller
-		return Thumb{W: w, H: h, Src: Url(hash, s.Name.String(), contentUri, previewToken)}
+		return &Thumb{W: w, H: h, Src: Url(hash, s.Name.String(), contentUri, previewToken)}
 	}
 
 	srcAspectRatio := float64(w) / float64(h)
@@ -66,11 +66,11 @@ func New(w, h int, hash string, s Size, contentUri, previewToken string) Thumb {
 
 	if srcAspectRatio > maxAspectRatio {
 		newW = s.Width
-		newH = int(math.Round(float64(newW) / srcAspectRatio))
+		newH = int(math.Ceil(float64(newW) / srcAspectRatio))
 	} else {
 		newH = s.Height
-		newW = int(math.Round(float64(newH) * srcAspectRatio))
+		newW = int(math.Ceil(float64(newH) * srcAspectRatio))
 	}
 
-	return Thumb{W: newW, H: newH, Src: Url(hash, s.Name.String(), contentUri, previewToken)}
+	return &Thumb{W: newW, H: newH, Src: Url(hash, s.Name.String(), contentUri, previewToken)}
 }
diff --git a/internal/thumb/viewer.go b/internal/thumb/viewer.go
index 355d59dc2..5f6f8b309 100644
--- a/internal/thumb/viewer.go
+++ b/internal/thumb/viewer.go
@@ -6,12 +6,13 @@ import (
 
 // Viewer represents thumbnail URLs for the photo/video viewer.
 type Viewer struct {
-	Fit720  Thumb `json:"fit_720"`
-	Fit1280 Thumb `json:"fit_1280"`
-	Fit1920 Thumb `json:"fit_1920"`
-	Fit2560 Thumb `json:"fit_2560"`
-	Fit4096 Thumb `json:"fit_4096"`
-	Fit7680 Thumb `json:"fit_7680"`
+	Fit720  *Thumb `json:"fit_720"`
+	Fit1280 *Thumb `json:"fit_1280"`
+	Fit1920 *Thumb `json:"fit_1920"`
+	Fit2560 *Thumb `json:"fit_2560"`
+	Fit4096 *Thumb `json:"fit_4096"`
+	Fit5120 *Thumb `json:"fit_5120"`
+	Fit7680 *Thumb `json:"fit_7680"`
 }
 
 // ViewerThumbs creates and returns a Viewer struct pointer with the required thumbnail URLs for the photo/video viewer.
@@ -21,8 +22,9 @@ func ViewerThumbs(fileWidth, fileHeight int, fileHash, contentUri, previewToken
 	// Get Viewer struct fields.
 	fields := reflect.ValueOf(thumbs).Elem()
 
-	// Remember the largest size needed, if any.
-	var maxSize Size
+	// Remember the maximum allowed size and the maximum actual size.
+	var maxSize = MaxSize()
+	var largestSize Size
 
 	// Iterate through all Viewer struct fields and set the best matching thumb size.
 	for i := 0; i < fields.NumField(); i++ {
@@ -43,13 +45,13 @@ func ViewerThumbs(fileWidth, fileHeight int, fileHash, contentUri, previewToken
 		}
 
 		// Remember this as the largest size needed if the original size is smaller than the thumb size.
-		if maxSize.Name == "" && s.Width >= fileWidth && s.Height >= fileHeight {
-			maxSize = s
+		if largestSize.Name == "" && (s.Width >= fileWidth && s.Height >= fileHeight || s.Width >= maxSize) {
+			largestSize = s
 		}
 
 		// Set the field value to the current size or the maximum size, if any.
-		if maxSize.Name != "" {
-			thumb.Set(reflect.ValueOf(New(fileWidth, fileHeight, fileHash, maxSize, contentUri, previewToken)))
+		if largestSize.Name != "" {
+			thumb.Set(reflect.ValueOf(New(fileWidth, fileHeight, fileHash, largestSize, contentUri, previewToken)))
 		} else {
 			thumb.Set(reflect.ValueOf(New(fileWidth, fileHeight, fileHash, s, contentUri, previewToken)))
 		}
diff --git a/internal/thumb/viewer_test.go b/internal/thumb/viewer_test.go
index 955b087de..087d313e7 100644
--- a/internal/thumb/viewer_test.go
+++ b/internal/thumb/viewer_test.go
@@ -24,7 +24,10 @@ func TestViewerThumbs(t *testing.T) {
 		assert.Equal(t, "https://example.com/t/011df944f313a05f89d170a561fad09ce6cef44e/12345678/fit_2560", result.Fit2560.Src)
 		assert.Equal(t, 2000, result.Fit4096.W)
 		assert.Equal(t, 1500, result.Fit4096.H)
-		assert.Equal(t, "https://example.com/t/011df944f313a05f89d170a561fad09ce6cef44e/12345678/fit_2560", result.Fit4096.Src)
+		assert.Equal(t, "https://example.com/t/011df944f313a05f89d170a561fad09ce6cef44e/12345678/fit_2560", result.Fit2560.Src)
+		assert.Equal(t, 2000, result.Fit5120.W)
+		assert.Equal(t, 1500, result.Fit5120.H)
+		assert.Equal(t, "https://example.com/t/011df944f313a05f89d170a561fad09ce6cef44e/12345678/fit_2560", result.Fit5120.Src)
 		assert.Equal(t, 2000, result.Fit7680.W)
 		assert.Equal(t, 1500, result.Fit7680.H)
 		assert.Equal(t, "https://example.com/t/011df944f313a05f89d170a561fad09ce6cef44e/12345678/fit_2560", result.Fit7680.Src)