Get a collection of products without image, ordered by an attribute

gistfile1.php

<?php

require_once 'app/Mage.php';
Mage::app();

$collection = Mage::getModel('catalog/product')->getCollection();

$collection->addAttributeToSelect(array('name', 'sku', 'isbn'))
  ->addAttributeToFilter('image', array('null' => true))
  ->addAttributeToSort('editorial');


foreach ($collection as $product) {
  echo "Product " . $product->getSku() . " has no image\n";
}