diff --git a/gtsam/geometry/Cal3.cpp b/gtsam/geometry/Cal3.cpp
index 31e9bf834..6183c6e5e 100644
--- a/gtsam/geometry/Cal3.cpp
+++ b/gtsam/geometry/Cal3.cpp
@@ -22,28 +22,25 @@
 #include <iostream>
 
 namespace gtsam {
-using namespace std;
 
 /* ************************************************************************* */
 Cal3::Cal3(double fov, int w, int h)
     : s_(0), u0_((double)w / 2.0), v0_((double)h / 2.0) {
   double a = fov * M_PI / 360.0;  // fov/2 in radians
-  fx_ =
-      (double)w / (2.0 * tan(a));  //    old formula: fx_ = (double) w * tan(a);
+  // old formula: fx_ = (double) w * tan(a);
+  fx_ = double(w) / (2.0 * tan(a));
   fy_ = fx_;
 }
 
 /* ************************************************************************* */
 Cal3::Cal3(const std::string& path)
     : fx_(320), fy_(320), s_(0), u0_(320), v0_(140) {
-  char buffer[200];
-  buffer[0] = 0;
-  sprintf(buffer, "%s/calibration_info.txt", path.c_str());
+  const auto buffer = path + std::string("/calibration_info.txt");
   std::ifstream infile(buffer, std::ios::in);
 
-  if (infile)
+  if (infile) {
     infile >> fx_ >> fy_ >> s_ >> u0_ >> v0_;
-  else {
+  } else {
     throw std::runtime_error("Cal3: Unable to load the calibration");
   }
 
@@ -51,9 +48,9 @@ Cal3::Cal3(const std::string& path)
 }
 
 /* ************************************************************************* */
-ostream& operator<<(ostream& os, const Cal3& cal) {
-  os << "{fx: " << cal.fx() << ", fy: " << cal.fy() << ", s:" << cal.skew()
-     << ", px:" << cal.px() << ", py:" << cal.py() << "}";
+std::ostream& operator<<(std::ostream& os, const Cal3& cal) {
+  os << "{ fx: " << cal.fx() << ", fy: " << cal.fy() << ", s: " << cal.skew()
+     << ", px: " << cal.px() << ", py: " << cal.py() << " }";
   return os;
 }
 
@@ -62,9 +59,9 @@ void Cal3::print(const std::string& s) const { gtsam::print((Matrix)K(), s); }
 
 /* ************************************************************************* */
 bool Cal3::equals(const Cal3& K, double tol) const {
-  return (std::fabs(fx_ - K.fx_) < tol) && (std::fabs(fy_ - K.fy_) < tol) &&
-         (std::fabs(s_ - K.s_) < tol) && (std::fabs(u0_ - K.u0_) < tol) &&
-         (std::fabs(v0_ - K.v0_) < tol);
+  return (std::fabs(fx_ - K.fx_) < tol && std::fabs(fy_ - K.fy_) < tol &&
+          std::fabs(s_ - K.s_) < tol && std::fabs(u0_ - K.u0_) < tol &&
+          std::fabs(v0_ - K.v0_) < tol);
 }
 
 /* ************************************************************************* */