diff --git a/lib/matplotlib/tests/test_image.py b/lib/matplotlib/tests/test_image.py
index 00a5ccc1058c..ae02a5072723 100644
--- a/lib/matplotlib/tests/test_image.py
+++ b/lib/matplotlib/tests/test_image.py
@@ -1170,7 +1170,7 @@ def __getitem__(self, item):
     def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
         func = getattr(ufunc, method)
         if "out" in kwargs:
-            raise NotImplementedError
+            return NotImplemented
         if len(inputs) == 1:
             i0 = inputs[0]
             unit = getattr(i0, "units", "dimensionless")
@@ -1190,11 +1190,16 @@ def __array_ufunc__(self, ufunc, method, *inputs, **kwargs):
                 unit = f"{u0}*{u1}"
             elif ufunc == np.divide:
                 unit = f"{u0}/({u1})"
+            elif ufunc in (np.greater, np.greater_equal,
+                           np.equal, np.not_equal,
+                           np.less, np.less_equal):
+                # Comparisons produce unitless booleans for output
+                unit = None
             else:
-                raise NotImplementedError
+                return NotImplemented
             out_arr = func(i0.view(np.ndarray), i1.view(np.ndarray), **kwargs)
         else:
-            raise NotImplementedError
+            return NotImplemented
         if unit is None:
             out_arr = np.array(out_arr)
         else: