I did a basic test with my new zeiss mutar 2x converter and the vivitar 2x converter. The difference after scanning is not that much that it is noticable after scanning. Maybe a 30x30cm print of a part of the image would show the difference at macro level. My opinion is that the vivitar it's image has somewhat more overall contrast than the mutar shows. The images where on the same film and shot directly after each other.