diff --git a/.gitignore b/.gitignore
index d9befd7..cc88be3 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,2 @@
-demo/out.jpg
+demo/*.jpg
+demo/*.pgm
diff --git a/CaptchaBuilder.php b/CaptchaBuilder.php
index eb3b0b6..084313c 100644
--- a/CaptchaBuilder.php
+++ b/CaptchaBuilder.php
@@ -203,7 +203,7 @@ public function build($width = 150, $height = 40, $font = null, $fingerprint = n
 
         // Apply effects
         $square = $width * $height;
-        $effects = $this->rand($square/5000, $square/2500);
+        $effects = $this->rand($square/3000, $square/1000);
         for ($e = 0; $e < $effects; $e++) {
             $function = $this->getScramblingFunction();
             for ($i=0; $i<$square/5000; $i++) {
diff --git a/demo/ocr.php b/demo/ocr.php
new file mode 100644
index 0000000..705e37e
--- /dev/null
+++ b/demo/ocr.php
@@ -0,0 +1,41 @@
+<?php
+
+include('../CaptchaBuilder.php');
+include('../PhraseBuilder.php');
+
+use Gregwar\Captcha\CaptchaBuilder;
+
+/**
+ * Generates 1000 captchas and try to read their code with the
+ * ocrad OCR
+ */
+
+$tests = 1000;
+$passed = 0;
+
+shell_exec('rm passed*.jpg');
+
+for ($i=0; $i<$tests; $i++) {
+    echo "Captcha $i/$tests... ";
+
+    $captcha = new CaptchaBuilder;
+
+    $captcha
+        ->build()
+        ->save('out.jpg', 20)
+        ;
+
+    shell_exec('convert out.jpg out.pgm');
+    $result = trim(shell_exec('ocrad out.pgm'));
+
+    if ($result == $captcha->getPhrase()) {
+        echo "passed at ocr\n";
+        shell_exec("cp out.jpg passed$passed.jpg");
+        $passed++;
+    } else {
+        echo "failed\n";
+    }
+}
+
+echo "\n";
+echo "Over, $passed/$tests readed with OCR\n";
diff --git a/demo/output.php b/demo/output.php
index ec1a5b9..ecb8902 100644
--- a/demo/output.php
+++ b/demo/output.php
@@ -8,6 +8,6 @@
 header('Content-type: image/jpeg');
 
 CaptchaBuilder::create()
-    ->build(300, 70)
+    ->build()
     ->output(20)
     ;