Index: trunk/src/com/drew/imaging/PhotographicConversions.java
===================================================================
--- trunk/src/com/drew/imaging/PhotographicConversions.java	(revision 4231)
+++ trunk/src/com/drew/imaging/PhotographicConversions.java	(revision 6127)
@@ -1,15 +1,21 @@
 /*
- * This is public domain software - that is, you can do whatever you want
- * with it, and include it software that is licensed under the GNU or the
- * BSD license, or whatever other licence you choose, including proprietary
- * closed source licenses.  I do ask that you leave this header in tact.
+ * Copyright 2002-2012 Drew Noakes
  *
- * If you make modifications to this code that you think would benefit the
- * wider community, please send me a copy and I'll post it on my site.
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
  *
- * If you make use of this code, I'd appreciate hearing about it.
- *   drew@drewnoakes.com
- * Latest version of this software kept at
- *   http://drewnoakes.com/
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ *
+ * More information about this project is available at:
+ *
+ *    http://drewnoakes.com/code/exif/
+ *    http://code.google.com/p/metadata-extractor/
  */
 package com.drew.imaging;
@@ -17,14 +23,19 @@
 /**
  * Contains helper methods that perform photographic conversions.
+ *
+ * @author Drew Noakes http://drewnoakes.com
  */
-public class PhotographicConversions
+public final class PhotographicConversions
 {
     public final static double ROOT_TWO = Math.sqrt(2);
 
-    private PhotographicConversions()
-    {}
+    private PhotographicConversions() throws Exception
+    {
+        throw new Exception("Not intended for instantiation.");
+    }
 
     /**
      * Converts an aperture value to its corresponding F-stop number.
+     *
      * @param aperture the aperture value to convert
      * @return the F-stop number of the specified aperture
@@ -32,9 +43,7 @@
     public static double apertureToFStop(double aperture)
     {
-        double fStop = Math.pow(ROOT_TWO, aperture);
-        return fStop;
+        return Math.pow(ROOT_TWO, aperture);
 
-        // Puzzle?!
-        // jhead uses a different calculation as far as i can tell...  this confuses me...
+        // NOTE jhead uses a different calculation as far as i can tell...  this confuses me...
         // fStop = (float)Math.exp(aperture * Math.log(2) * 0.5));
     }
@@ -42,4 +51,5 @@
     /**
      * Converts a shutter speed to an exposure time.
+     *
      * @param shutterSpeed the shutter speed to convert
      * @return the exposure time of the specified shutter speed
@@ -47,5 +57,5 @@
     public static double shutterSpeedToExposureTime(double shutterSpeed)
     {
-        return (float)(1 / Math.exp(shutterSpeed * Math.log(2)));
+        return (float) (1 / Math.exp(shutterSpeed * Math.log(2)));
     }
 }