diff --git a/wagtail/wagtailimages/backends/base.py b/wagtail/wagtailimages/backends/base.py
index 25b7e882d..0c6d34951 100644
--- a/wagtail/wagtailimages/backends/base.py
+++ b/wagtail/wagtailimages/backends/base.py
@@ -130,3 +130,8 @@ class BaseImageBackend(object):
         """
         resized_image = self.resize_to_min(image, size)
         return self.crop_to_centre(resized_image, size)
+
+
+    def no_operation(self, image, param):
+        """Return the image unchanged"""
+        return image
diff --git a/wagtail/wagtailimages/models.py b/wagtail/wagtailimages/models.py
index 24fd1f0bf..781b5cd67 100644
--- a/wagtail/wagtailimages/models.py
+++ b/wagtail/wagtailimages/models.py
@@ -1,5 +1,6 @@
 import StringIO
 import os.path
+import re
 
 from taggit.managers import TaggableManager
 
@@ -150,6 +151,7 @@ class Filter(models.Model):
         'width': 'resize_to_width',
         'height': 'resize_to_height',
         'fill': 'resize_to_fill',
+        'original': 'no_operation',
     }
 
     def __init__(self, *args, **kwargs):
@@ -157,22 +159,34 @@ class Filter(models.Model):
         self.method = None  # will be populated when needed, by parsing the spec string
 
     def _parse_spec_string(self):
-        # parse the spec string, which is formatted as (method)-(arg),
-        # and save the results to self.method_name and self.method_arg
-        try:
-            (method_name_simple, method_arg_string) = self.spec.split('-')
-            self.method_name = Filter.OPERATION_NAMES[method_name_simple]
+        # parse the spec string and save the results to
+        # self.method_name and self.method_arg. There are various possible
+        # formats to match against:
+        # 'original'
+        # 'width-200'
+        # 'max-320x200'
 
-            if method_name_simple in ('max', 'min', 'fill'):
-                # method_arg_string is in the form 640x480
-                (width, height) = [int(i) for i in method_arg_string.split('x')]
-                self.method_arg = (width, height)
-            else:
-                # method_arg_string is a single number
-                self.method_arg = int(method_arg_string)
+        if self.spec == 'original':
+            self.method_name = Filter.OPERATION_NAMES['original']
+            self.method_arg = None
+            return
 
-        except (ValueError, KeyError):
-            raise ValueError("Invalid image filter spec: %r" % self.spec)
+        match = re.match(r'(width|height)-(\d+)$', self.spec)
+        if match:
+            self.method_name = Filter.OPERATION_NAMES[match.group(1)]
+            self.method_arg = int(match.group(2))
+            return
+
+        match = re.match(r'(max|min|fill)-(\d+)x(\d+)$', self.spec)
+        if match:
+            self.method_name = Filter.OPERATION_NAMES[match.group(1)]
+            width = int(match.group(2))
+            height = int(match.group(3))
+            self.method_arg = (width, height)
+            return
+
+        # Spec is not one of our recognised patterns
+        raise ValueError("Invalid image filter spec: %r" % self.spec)
 
     def process_image(self, input_file, backend_name='default'):
         """
diff --git a/wagtail/wagtailimages/tests.py b/wagtail/wagtailimages/tests.py
index 00d1245e6..a2dae86b2 100644
--- a/wagtail/wagtailimages/tests.py
+++ b/wagtail/wagtailimages/tests.py
@@ -107,6 +107,13 @@ class TestRenditions(TestCase):
         self.assertEqual(rendition.width, 160)
         self.assertEqual(rendition.height, 120)
 
+    def test_resize_to_original(self):
+        rendition = self.image.get_rendition('original')
+
+        # Check size
+        self.assertEqual(rendition.width, 640)
+        self.assertEqual(rendition.height, 480)
+
     def test_cache(self):
         # Get two renditions with the same filter
         first_rendition = self.image.get_rendition('width-400')
@@ -153,6 +160,13 @@ class TestRenditionsWand(TestCase):
         self.assertEqual(rendition.width, 160)
         self.assertEqual(rendition.height, 120)
 
+    def test_resize_to_original(self):
+        rendition = self.image.get_rendition('original')
+
+        # Check size
+        self.assertEqual(rendition.width, 640)
+        self.assertEqual(rendition.height, 480)
+
     def test_cache(self):
         # Get two renditions with the same filter
         first_rendition = self.image.get_rendition('width-400')