diff --git a/core/utils.py b/core/utils.py
index 82fc78a7..a815975b 100644
--- a/core/utils.py
+++ b/core/utils.py
@@ -82,40 +82,47 @@ def get_semester_code(d: Optional[date] = None) -> str:
     return "P" + str(start.year)[-2:]
 
 
-def resize_image(im: Image, edge: int, img_format: str):
-    """Resize an image to fit the given edge length and format."""
+def resize_image(
+    im: Image, edge: int, img_format: str, *, optimize: bool = True
+) -> ContentFile:
+    """Resize an image to fit the given edge length and format.
+
+    Args:
+        im: the image to resize
+        edge: the length that the greater side of the resized image should have
+        img_format: the target format of the image ("JPEG", "PNG", "WEBP"...)
+        optimize: Should the resized image be optimized ?
+    """
     (w, h) = im.size
     ratio = edge / max(w, h)
     (width, height) = int(w * ratio), int(h * ratio)
-    return resize_image_explicit(im, (width, height), img_format)
+    return resize_image_explicit(im, (width, height), img_format, optimize=optimize)
 
 
-def resize_image_explicit(im: Image, size: tuple[int, int], img_format: str):
-    """Resize an image to the given size and format."""
+def resize_image_explicit(
+    im: Image, size: tuple[int, int], img_format: str, *, optimize: bool = True
+) -> ContentFile:
+    """Resize an image to the given size and format.
+
+    Args:
+        im: the image to resize
+        size: the target dimension, as a [width, height] tuple
+        img_format: the target format of the image ("JPEG", "PNG", "WEBP"...)
+        optimize: Should the resized image be optimized ?
+    """
     img_format = img_format.upper()
     content = BytesIO()
     # use the lanczos filter for antialiasing and discard the alpha channel
-    im = im.resize((size[0], size[1]), Resampling.LANCZOS)
+    if size != im.size:
+        im = im.resize((size[0], size[1]), Resampling.LANCZOS)
     if img_format == "JPEG":
         # converting an image with an alpha channel to jpeg would cause a crash
         im = im.convert("RGB")
     try:
-        im.save(
-            fp=content,
-            format=img_format,
-            quality=90,
-            optimize=True,
-            progressive=True,
-        )
+        im.save(fp=content, format=img_format, optimize=optimize)
     except IOError:
         PIL.ImageFile.MAXBLOCK = im.size[0] * im.size[1]
-        im.save(
-            fp=content,
-            format=img_format,
-            quality=90,
-            optimize=True,
-            progressive=True,
-        )
+        im.save(fp=content, format=img_format, optimize=optimize)
     return ContentFile(content.getvalue())
 
 
diff --git a/sas/models.py b/sas/models.py
index e63ef8b0..4248be50 100644
--- a/sas/models.py
+++ b/sas/models.py
@@ -117,7 +117,11 @@ class Picture(SasFile):
         # meant to be shown on the website, but rather to keep the real image
         # for less frequent cases (like downloading the pictures of an user)
         extension = self.mime_type.split("/")[-1]
-        file = resize_image(im, max(im.size), extension)
+        # the HD version of the image doesn't need to be optimized, because :
+        # - it isn't frequently queried
+        # - optimizing large images takes a lot time, which greatly hinders the UX
+        # - photographers usually already optimize their images
+        file = resize_image(im, max(im.size), extension, optimize=False)
         thumb = resize_image(im, 200, "webp")
         compressed = resize_image(im, 1200, "webp")
         if overwrite: