The Tenax I is simple and a bit primitive. The Tenax II is a high-quality 35 with interchangeable lenses and quite innovative for its time. The life-size finder, bright RF patch, sharp lenses and rapid advance make for a easy-to-operate camera with beautiful handling. Unfortunately, it uses the square 24mm X 24mm format. This can make getting film processed a bit of a challenge unless you are into do-it-yourself. My local lab cannot print or digitize negatives except one at a time—quite expensive. I enjoy mine. It has made film photography fun again. Cheers, WES LODER