Well, I have been toying with this lens for a while. Everything looked good on the ground glass, and thanks to J. Bruner's video on calculating f stop, I was able to determine everything I needed to make an image. It gives me about f3.16, focal length is 143mm The result is something quite a bit different from what I usually get. I like it. If you have a speed graphic and have not tried this yet, I strongly recommend you do. Any cheap lens will work. You may be surprised with what you get.