Display info from custom fields in all images’ HTML

You can create a filter using the “wp_get_attachment_image_attributes” hook. Place this in your functions.php file.

function filter_image_title($attr, $attachment = null){
        //Find your $photographer with $attachment->ID
        $attr['title'] .= ' (' . __('Photographed by', 'foobar') . ' ' . $photographer . ')';
        return $attr;
}
add_filter('wp_get_attachment_image_attributes', 'filter_image_title', 10, 2);