diff --git a/README.md b/README.md
index 0125bf2d..7b8a983c 100644
--- a/README.md
+++ b/README.md
@@ -47,8 +47,8 @@ Add the facade of this package to the `$aliases` array.
 * Image::resize - Resize current image based on given width and/or height
 * Image::grab - Cut out a detail of the image in given ratio and resize to output size
 * Image::insert - Insert another image on top of the current image
-* Image::brightness - Changes brightness of current image (from -255 to +255)
-* Image::contrast - Changes contrast of current image (from -100 to +100)
+* Image::brightness - Changes brightness of current image (-100 = min brightness, 0 = no change, +100 = max brightness)
+* Image::contrast - Changes contrast of current image (-100 = min contrast, 0 = no change, +100 = max contrast)
 * Image::pixelate - Pixelate current image
 * Image::greyscale - Turn current image into a greyscale version
 * Image::text - Write text in current image
diff --git a/src/Intervention/Image/Image.php b/src/Intervention/Image/Image.php
index 94e34bca..1fbcfe9b 100644
--- a/src/Intervention/Image/Image.php
+++ b/src/Intervention/Image/Image.php
@@ -429,7 +429,15 @@ class Image
      */
     public function brightness($level)
     {
+        // normalize level
+        if ($level >= -100 && $level <= 100) {
+            $level = $level * 2.55;
+        } else {
+            throw new Exception('Brightness level must be between -100 and +100');
+        }
+
         imagefilter($this->resource, IMG_FILTER_BRIGHTNESS, $level);
+
         return $this;
     }
 
@@ -441,7 +449,15 @@ class Image
      */
     public function contrast($level)
     {
+        // normalize level
+        if ($level >= -100 && $level <= 100) {
+            $level = $level * (-1);
+        } else {
+            throw new Exception('Contrast level must be between -100 and +100');
+        }
+
         imagefilter($this->resource, IMG_FILTER_CONTRAST, $level);
+
         return $this;
     }
 
@@ -455,6 +471,7 @@ class Image
     public function pixelate($size = 10, $advanced = true)
     {
         imagefilter($this->resource, IMG_FILTER_PIXELATE, $size, $advanced);
+
         return $this;
     }
 
@@ -466,6 +483,7 @@ class Image
     public function grayscale()
     {
         imagefilter($this->resource, IMG_FILTER_GRAYSCALE);
+
         return $this;
     }
 
@@ -477,6 +495,7 @@ class Image
     public function greyscale()
     {
         $this->grayscale();
+
         return $this;
     }
 
@@ -488,6 +507,7 @@ class Image
     public function reset()
     {
         $this->setProperties($this->dirname .'/'. $this->basename);
+
         return $this;
     }
 
diff --git a/tests/ImageTest.php b/tests/ImageTest.php
index 7c642690..7475df06 100644
--- a/tests/ImageTest.php
+++ b/tests/ImageTest.php
@@ -349,19 +349,47 @@ class ImageTest extends PHPUnit_Framework_Testcase
     public function testBrightnessImage()
     {
         $img = $this->getTestImage();
-        $img->brightness(50);
-        $img->brightness(-50);
+        $img->brightness(100);
+        $img->brightness(-100);
         $this->assertInstanceOf('Intervention\Image\Image', $img);
     }
 
     public function testContrastImage()
     {
         $img = $this->getTestImage();
-        $img->contrast(50);
-        $img->contrast(-50);
+        $img->contrast(100);
+        $img->contrast(-100);
         $this->assertInstanceOf('Intervention\Image\Image', $img);
     }
 
+    public function testBrightnessException()
+    {
+        $img = $this->getTestImage();
+
+        // test exception
+        try {
+            $img->brightness(255);
+        } catch (Exception $e) {
+            return;
+        }
+
+        $this->fail('An expected exception has not been raised for brightness filter');
+    }
+
+    public function testContrastException()
+    {
+        $img = $this->getTestImage();
+
+        // test exception
+        try {
+            $img->contrast(255);
+        } catch (Exception $e) {
+            return;
+        }
+
+        $this->fail('An expected exception has not been raised for contrast filter');
+    }
+
     public function testStaticCallMake()
     {
         $img = Image::make('public/test.jpg');