diff --git a/optika/_tests/test_systems.py b/optika/_tests/test_systems.py
index 3f4d256..1a554b4 100644
--- a/optika/_tests/test_systems.py
+++ b/optika/_tests/test_systems.py
@@ -257,6 +257,7 @@ def test_rayfunction_default(self, a: optika.systems.AbstractSequentialSystem):
     axis_pixel=na.Cartesian2dVectorArray("detector_x", "detector_y"),
     timedelta_exposure=1 * u.s,
     num_pixel=na.Cartesian2dVectorArray(128, 128),
+    transformation=na.transformations.Cartesian3dTranslation(z=1 * u.mm),
     is_field_stop=True,
 )
 
diff --git a/optika/sensors/_sensors.py b/optika/sensors/_sensors.py
index 4c54c07..9388d2e 100644
--- a/optika/sensors/_sensors.py
+++ b/optika/sensors/_sensors.py
@@ -100,7 +100,7 @@ def readout(
         Parameters
         ----------
         rays
-            A set of incident rays in global coordinates to measure.
+            A set of incident rays in local coordinates to measure.
         timedelta
             The exposure time of the measurement.
             If :obj:`None` (the default), the value in :attr:`timedelta_exposure`
@@ -114,9 +114,6 @@ def readout(
         if timedelta is None:
             timedelta = self.timedelta_exposure
 
-        if self.transformation is not None:
-            rays = self.transformation.inverse(rays)
-
         where = where & rays.unvignetted
 
         rays = dataclasses.replace(
diff --git a/optika/systems.py b/optika/systems.py
index 7e548ab..b3b564c 100644
--- a/optika/systems.py
+++ b/optika/systems.py
@@ -603,8 +603,8 @@ def raytrace(
     ) -> optika.rays.RayFunctionArray:
         """
         Given the wavelength, field position, and pupil position of some input
-        rays, trace those rays through the system and return the result,
-        including all intermediate rays.
+        rays, trace those rays through the system and return the result in
+        global coordinates, including all intermediate rays.
 
         Parameters
         ----------
@@ -634,7 +634,8 @@ def raytrace(
 
         See Also
         --------
-        rayfunction : Similar to `raytrace` except it only returns the rays at the last surface.
+        rayfunction : Similar to `raytrace` except it only returns the rays at
+            the last surface in local coordinates.
         """
 
         if axis is None:
@@ -683,7 +684,7 @@ def rayfunction(
         """
         Given the wavelength, field position, and pupil position of some input
         rays, trace those rays through the system and return the resulting
-        rays at the last surface.
+        rays in local coordinates at the last surface.
 
         Parameters
         ----------
@@ -710,7 +711,8 @@ def rayfunction(
 
         See Also
         --------
-        raytrace : Similar to `rayfunction` except it computes all the intermediate rays.
+        raytrace : Similar to `rayfunction` except it computes all the
+            intermediate rays, and it returns results in global coordinates.
         """
 
         axis = "_dummy"
@@ -723,13 +725,25 @@ def rayfunction(
             normalized_field=normalized_field,
             normalized_pupil=normalized_pupil,
         )
-        return raytrace[{axis: ~0}]
+        rayfunction = raytrace[{axis: ~0}]
+        rays = rayfunction.outputs
+
+        if self.sensor.transformation is not None:
+            rays = self.sensor.transformation.inverse(rays)
+
+        rayfunction.outputs = rays
+
+        return rayfunction
 
     @functools.cached_property
     def rayfunction_default(self) -> optika.rays.RayFunctionArray:
         """
-        Computes the rays at the last surface in the system as a function of
-        input wavelength and position using :attr:`grid_input`.
+        Computes the rays in local coordinates at the last surface in the system
+        as a function of input wavelength and position using :attr:`grid_input`.
+
+        This property is cached to increase performance.
+        If :attr:`grid_input` is updated, the cache must be cleared with
+        ``del system.rayfunction_default`` before calling property.
         """
         return self.rayfunction()