Just a tiny fix of two typos

- Fixed a typo in the help text
- Fixed a typo in a comment line

modules/sfm/samples/scene_reconstruction.cpp

@@ -20,7 +20,7 @@ static void help() {
       << "        example_sfm_scene_reconstruction <path_to_file> <f> <cx> <cy>\n"
       << " where: path_to_file is the file absolute path into your system which contains\n"
       << "        the list of images to use for reconstruction. \n"
-      << "        f  is the focal lenght in pixels. \n"
+      << "        f  is the focal length in pixels. \n"
       << "        cx is the image principal point x coordinates in pixels. \n"
       << "        cy is the image principal point y coordinates in pixels. \n"
       << "------------------------------------------------------------------------------------\n\n"
@@ -60,7 +60,7 @@ int main(int argc, char* argv[])
   getdir( argv[1], images_paths );
 
 
-  // Build instrinsics
+  // Build intrinsics
 
   float f  = atof(argv[2]),
         cx = atof(argv[3]), cy = atof(argv[4]);
@@ -156,4 +156,4 @@ int main(int argc, char* argv[])
   window.spin();
 
   return 0;
-}
\ No newline at end of file
+}