diff --git a/src/com/jwetherell/motion_detection/detection/Comparer.java b/src/com/jwetherell/motion_detection/detection/Comparer.java
index e930e29..47484b9 100644
--- a/src/com/jwetherell/motion_detection/detection/Comparer.java
+++ b/src/com/jwetherell/motion_detection/detection/Comparer.java
@@ -32,6 +32,7 @@ public void setDebugMode(int m) {
 	// compare two images.
 	public Comparison compare(State s1, State s2) {
 		if (s1==null || s2==null) return null;
+		if (s1.getWidth()!=s2.getWidth() || s1.getHeight()!=s2.getHeight()) return null;
 		
 		int cx = comparex;
 		if (cx > s1.getWidth()) cx = s1.getWidth();
@@ -54,8 +55,9 @@ public Comparison compare(State s1, State s2) {
 			if (debugMode > 0) output.append("|");
 			ty = y*by;
 			for (int x = 0; x < cx; x++) {
-				int b1 = aggregateMapArea(s1.getMap(), x*bx, ty, bx, by);
-				int b2 = aggregateMapArea(s2.getMap(), x*bx, ty, bx, by);
+				int tx = x*bx;
+				int b1 = aggregateMapArea(s1.getMap(), tx, ty, bx, by);
+				int b2 = aggregateMapArea(s2.getMap(), tx, ty, bx, by);
 				int diff = Math.abs(b1 - b2);
 				variance[y][x] = diff;
 				// the difference in a certain region has passed the threshold value
@@ -73,7 +75,7 @@ public Comparison compare(State s1, State s2) {
 	
 	private static int aggregateMapArea(int[][] map, int ox, int oy, int w, int h) {
 		if (map==null) return Integer.MIN_VALUE;
-		
+
 		int t = 0;
 		for (int i = 0; i < h; i++) {
 			int ty = oy+i;
diff --git a/src/com/jwetherell/motion_detection/detection/MotionDetection.java b/src/com/jwetherell/motion_detection/detection/MotionDetection.java
index 4336da7..5a63a70 100644
--- a/src/com/jwetherell/motion_detection/detection/MotionDetection.java
+++ b/src/com/jwetherell/motion_detection/detection/MotionDetection.java
@@ -21,10 +21,10 @@ public abstract class MotionDetection {
 	private static int[] mPrevious = null;
 	private static int mPreviousWidth = 0;
 	private static int mPreviousHeight = 0;
-	private static State mPreviousStatus = null;
+	private static State mPreviousState = null;
 	
 	public static int[] getPrevious() {
-		return (mPrevious!=null)?mPrevious.clone():null;
+		return ((mPrevious!=null)?mPrevious.clone():null);
 	}
 
 	protected static boolean isDifferentComparingState(int[] first, int width, int height) {
@@ -32,18 +32,13 @@ protected static boolean isDifferentComparingState(int[] first, int width, int h
 		if (first.length != mPrevious.length) return true;
 		if (mPreviousWidth != width || mPreviousHeight != height) return true;
 
-		if (mPreviousStatus==null) {
-			mPreviousStatus = new State(mPrevious, width, height);
-			return false;
-		}
+		if (mPreviousState==null) mPreviousState = new State(mPrevious, mPreviousWidth, mPreviousHeight);
 
-		State state = new State(first, (width/10), (height/10)); 
-		Comparer ic = new Comparer(20, 20, 0);
+		State state = new State(first, width, height); 
+		Comparer ic = new Comparer((width/10), (height/10), 0);
 		ic.setDebugMode(1);
-		Comparison c = ic.compare(mPreviousStatus, state);
-		
-		mPreviousStatus = new State(mPrevious, width, height);
-		
+		Comparison c = ic.compare(mPreviousState, state);
+
 		boolean different = c.isDifferent();
 		String output = "isDifferent="+different;
 		if (different) {
@@ -52,6 +47,8 @@ protected static boolean isDifferentComparingState(int[] first, int width, int h
 			Log.d(TAG, output);
 		}
 
+		mPreviousState = state;
+		
 		return different;
 	}
 	
diff --git a/src/com/jwetherell/motion_detection/image/ImageProcessing.java b/src/com/jwetherell/motion_detection/image/ImageProcessing.java
index 7499953..c4564a8 100644
--- a/src/com/jwetherell/motion_detection/image/ImageProcessing.java
+++ b/src/com/jwetherell/motion_detection/image/ImageProcessing.java
@@ -60,14 +60,14 @@ public static float[] convertToHSL(int r, int g, int b) {
             }
         }
         
-        //convert to 0-360
+        //convert to 0-360 (degrees)
         HSL[H] *= 60;
         if (HSL[H]<0) HSL[H] += 360;
         
-        //convert to 0-100
+        //convert to 0-100 (percent)
         HSL[S] *= 100;
-        HSL[L] *= 100; 
-
+        HSL[L] *= 100;
+        
 		return HSL;
 	}
 
@@ -82,7 +82,7 @@ public static float getBrightnessAtPoint(int pixel) {
         float red = r / 255;
         float green = g / 255;
         float blue = b / 255;
-        float h=0,s=0,l=0;
+        float h=0,l=0;
         
 		float minComponent = Math.min(red, Math.min(green, blue));
         float maxComponent = Math.max(red, Math.max(green, blue));
@@ -90,14 +90,7 @@ public static float getBrightnessAtPoint(int pixel) {
         
         l = (maxComponent + minComponent) / 2;
 
-        if(range == 0) { // Monochrome image
-        	h = s = 0;
-        } else {
-            s = 	(l > 0.5) ? 
-		    				range / (2 - range) 
-		    			: 
-		    				range / (maxComponent + minComponent);
-            
+        if(range > 0) {
             if(red == maxComponent) {
             	h = (blue - green) / range;
             } else if(green == maxComponent) {
@@ -112,8 +105,7 @@ public static float getBrightnessAtPoint(int pixel) {
         if (h<0) h += 360;
         
         //convert to 0-100
-        s *= 100;
-        l *= 100; 
+        l *= 100;
 
         //Convert the HSL into a single "brightness" representation
 		return (float)(l * 0.5 + ((h / 360) * 50));