get_post_thumbnail_caption()

<?php
/**
 * @package Wordspop
 * @subpackage Fotofolio_Landscape
 */

add_theme_support('webfont');

/**
 * Load initial WPop script
 */
require_once dirname(__FILE__) . '/libs/wpop/init.php';

function get_post_thumbnail_caption() {
  global $post;

  $thumb_id = get_post_thumbnail_id($post->id);

  $args = array(
    'post_type' => 'attachment',
    'post_status' => null,
    'post_parent' => $post->ID,
    'include'  => $thumb_id
    );

   $thumbnail_image = get_posts($args);

   if ($thumbnail_image && isset($thumbnail_image[0])) {
     //show thumbnail title
     //return $thumbnail_image[0]->post_title;

     //Uncomment to show the thumbnail caption
     return $thumbnail_image[0]->post_excerpt;

     //Uncomment to show the thumbnail description
     //return $thumbnail_image[0]->post_content;

     //Uncomment to show the thumbnail alt field
     //$alt = get_post_meta($thumbnail_id, '_wp_attachment_image_alt', true);
     //if(count($alt)) return $alt;
  }
  else {
    return false;
  }
}