diff --git a/gtsam/geometry/CameraSet.h b/gtsam/geometry/CameraSet.h
index 27c0a78f3..3a34ca1fd 100644
--- a/gtsam/geometry/CameraSet.h
+++ b/gtsam/geometry/CameraSet.h
@@ -32,7 +32,7 @@ namespace gtsam {
 template<class CAMERA>
 class CameraSet: public std::vector<CAMERA> {
 
-private:
+protected:
 
   /**
    * 2D measurement and noise model for each of the m views
@@ -45,6 +45,10 @@ private:
 
 public:
 
+  /// Definitions for blocks of F
+  typedef Eigen::Matrix<double, ZDim, Dim> MatrixZD; // F
+  typedef std::pair<Key, MatrixZD> FBlock; // Fblocks
+
   /**
    * print
    * @param s optional string naming the factor
@@ -70,7 +74,7 @@ public:
   }
 
   /**
-   *  project, with derivatives in this, point, and calibration
+   * Project a point, with derivatives in this, point, and calibration
    * throws CheiralityException
    */
   std::vector<Z> project(const Point3& point, boost::optional<Matrix&> F =