julienmonnerie/site/controllers/gallery.php

<?php

return function ($pages, $page) {

    // Get exhibition page object
    $exhibitionsPage = $pages->template('exhibitions')->first();

    // Get image files section content
    $images = $page->files()->template("full_screen_image")->sortBy('sort');

    return [
        'exhibitionsPage' => $exhibitionsPage,
        'images' => $images
    ];
};