I believe he is using a 50mm lens. if you reverse it with a ring you will get about 20 diopters. With the tube it only increases. Actual numbers would require some expensive measuring equipment and a ton of time.
I like it. I am always looking for hacks like these to put things in unused spaces. I am trying to sell my wife on this idea, she loves the pics. Now I just need to get my shop back in running order.Two thumbs up ! ! !
A beginner's guide to Arduino