Hello everybody,

New here and to lf photography, and just bought me a Fuji gx617, I tried searching the web and not have been very successful in finding what I want to know, maybe because I don't understand the answer or I am not asking the right question? I am no Forest Gump but then I've never been confused for Einstein either, probably more towards Forest Gump. Any way, the first question is I got a ground glass viewer, it works great for composition but lacks a little for focusing, so I bought a fresnel lens for it, where does the fresnel go or attach? does it replace the ground glass or mount to it? It doesn't fit in from the front, and the viewer wont attach with it on the front! My second question is can someone point me to a good source about the number on my lenses, how do you focus reliably using the numbers? Third
question is, does anybody know of the website DOFmaster? I am not sure what camera to pick? aps 6x7 etc.. or the circle of confusion?
Anyway, If someone could be so kind as to get me pointed in the right direction it sure would be greatly appreciated.

Thanks again

John