@WPDragon i should have mentioned i just made up the markup without testing or looking at lightbox documentation — also if your using a repeater try this for testing:
<?php //For Use with Repeater Field
$videos = get_field('video');
$videos_raw = get_field('video', FALSE, FALSE);
//Add the Thubmnail to the $videos object
foreach($videos_raw as $key => $video_raw) :
$videos[$key]['video_thumb'] = get_video_thumbnail_uri($video_raw['field_5449746362c3d']);
//Replace 'field_5449746362c3d' with your field's Field key (obtainable by going to screen options in the fields admin, and setting 'Show Field Key' to 'Yes')
endforeach;
//Loop through the $videos object
foreach($videos as $video): ?>
VIDEO THUMB URL: <?php echo $video['video_thumb']; ?>
VIDEO EMBED: <?php echo $video['video_url'] ?>
<? endforeach; ?>
