Eric Renner and Nancy Spencer run "The Pinhole Resource" (Address: Star
Rte. 15 Box 1355 San Lorenzo, NM). They have worked out a remarkable
amount of these technical issues and will send it to you. They also have a
web-site with this info, but I donnot have the URL handy. You might search
it out.
Hope this helps.
Jon Bailey
>Am I right to use formula for hole diameter D:
> SQRT(Focal lenght)
>D= -------------------- [mm]
> 44
>
>Since I have enough quantity of b/w 9x12 sheet film, film holders,
>cassetes, Jobo tank for development of 6 pieces at time, home made
>enlargerer; can someone recomend me a combination of hole diameter
>and focal lenght for this format. I am esspecialy interested is
>there combination that can allow enlargment and by what ratio?