function allphotos_shortcode(){

  $images = get_field('fl_gallery');

  if( $images ) {
      $output .= '<ul id="kalpht">';
      foreach( $images as $image ) :
              $output .= '<li><a class="x-img-link" href="' . $image['url'] .'" data-options="thumbnail:'' . $image['sizes']['mini-me'] . ''"><img src="' . $image['sizes']['mini-me'] . '" alt="' . $image['alt'] . '" /></a></li>';
         endforeach;
      $output .= '</ul>' . do_shortcode('[lightbox opacity="0.9" thumbnails="true"]');
}

return $output;
 }

add_shortcode('allphotos', 'allphotos_shortcode');