diff --git a/gtsam/geometry/Cal3_S2.h b/gtsam/geometry/Cal3_S2.h
index c134860bb..03c6bff3f 100644
--- a/gtsam/geometry/Cal3_S2.h
+++ b/gtsam/geometry/Cal3_S2.h
@@ -165,6 +165,16 @@ public:
    */
   Vector3 calibrate(const Vector3& p) const;
 
+  /// "Between", subtracts calibrations. between(p,q) == compose(inverse(p),q)
+  inline Cal3_S2 between(const Cal3_S2& q,
+      boost::optional<Matrix&> H1=boost::none,
+      boost::optional<Matrix&> H2=boost::none) const {
+    if(H1) *H1 = -eye(5);
+    if(H2) *H2 = eye(5);
+    return Cal3_S2(q.fx_-fx_, q.fy_-fy_, q.s_-s_, q.u0_-u0_, q.v0_-v0_);
+  }
+
+
   /// @}
   /// @name Manifold
   /// @{
diff --git a/gtsam/geometry/tests/testCal3_S2.cpp b/gtsam/geometry/tests/testCal3_S2.cpp
index d77a534d6..86c0b7e33 100644
--- a/gtsam/geometry/tests/testCal3_S2.cpp
+++ b/gtsam/geometry/tests/testCal3_S2.cpp
@@ -93,6 +93,17 @@ TEST( Cal3_S2, retract)
   CHECK(assert_equal(d,K.localCoordinates(actual),1e-7));
 }
 
+/* ************************************************************************* */
+TEST(Cal3_S2, between) {
+  Cal3_S2 k1(5, 5, 5, 5, 5), k2(5, 6, 7, 8, 9);
+  Matrix H1, H2;
+
+  EXPECT(assert_equal(Cal3_S2(0,1,2,3,4), k1.between(k2, H1, H2)));
+  EXPECT(assert_equal(-eye(5), H1));
+  EXPECT(assert_equal(eye(5), H2));
+
+}
+
 /* ************************************************************************* */
 int main() {
   TestResult tr;